METHODS FOR CULTIVATING RECOMBINANT EUKARYOTIC CELLS FOR IMPROVED PRODUCTION OF RECOMBINANT PROTEIN

Abstract

The specification describes a composition comprising an improved eukaryotic cell culture medium, which can be used for the production of a protein of interest. Taurine can be added to the serum-free medium or the chemically defined medium to increase the production of a protein of interest. Methods for recombinantly expressing high levels of protein using the compositions comprising the medium are included.

Description

FIELD The invention relates to a medium and methods for cell culture and for the production of recombinant proteins. The invention specifically relates to a taurine-supplemented medium and methods thereof for the culture of recombinant eukaryotic cells for the production of protein biotherapeutic agents. BACKGROUND Taurine is an organic acid, often referred to as a β-amylo acid, which is found in high concentrations in most tissues and is a derivative of the amino acid cholesteine ​​(Huxtable, kJ., 1992, Physiol Rev, 72:101-163). Taurine Structure 231038 CAB Taurine is present in many tissues of humans and other mammalian species, e.g., brain, retina, myocardium, skeletal and smooth muscle, platelets, and neutrophils. Taurine is known to aid in osmoregulation, membrane stabilization, and anti-inflammation, and it also regulates mitochondrial protein synthesis by increasing electron transport chain activity, which protects against superoxide generation (Jong et al., 2010, Journal of Biomedical Science 17(Suppl 1):S25; Jong et al., 2012, Amino Acids 42:2223-2232sw). In primary neuronal cultures, taurine has been characterized as a cytoprotective agent due to its suppression of glutamate-induced toxicity. Several taurine-containing embryo culture media have been developed. Cell culture techniques involving amino acid feeding have a long history of use in the production of recombinant proteins from cultured cells. Amino acids are biosynthetic precursors, energy sources, osmolytes, and the like, and their use in production cultures is strongly correlated with sustained cell growth and productivity. However, the physiological events that contribute to high-performance protein productivity and expression are numerous, and competing metabolic activities and transport mechanisms make designing feeding strategies challenging. The type of amino acid supplementation and the timing of addition may also impact the quality of the protein produced in culture (Altamirano et al., 2006, Electron. J. Biotechnol. 9:61-67). Byproduct accumulation is frequently problematic in production cell culture and is considered a consequence of nutrient imbalance in the cell culture, which ultimately inhibits cell growth (Fan et al., Biotechnol. Bioeng. 2015). Mar; 112(3):521-35). Hypotaurine or an analogue or precursor thereof has been suggested in cell culture to achieve the desired results of reducing the color intensity of a composition comprising a recombinantly produced polypeptide (W020lJl45098A1, published September 18, 2014). A cell culture medium including taurine that promotes the maturation of immature retinal pigment epithelial cells into mature retinal pigment epithelial cells has also been described (WO2013184809A1, published December 12, 2013). However, optimization of recombinant protein productivity in taurine-supplemented cultures has not been recognized in the art. Cell culture processes that increase the productivity of recombinantly expressed proteins while minimizing the production of potentially toxic cellular metabolic byproducts, such as ammonia, are highly desirable.Any consistent increase in productivity can mean a significantly larger commercial-scale supply of a biotherapeutic product. Therefore, there is a need in the technique for a method and methods to cultivate mammalian cells, where the medium makes possible the growth and maintenance of healthy and strong cells, and the production of high titers of biopharmaceutical drug substance. SYNTHESIS The inventors have surprisingly discovered that including taurine in a cell culture medium increases cell-specific productivity and results in less ammonia byproduct per cell. Various feeding strategies incorporating taurine allow for the production of higher-titer proteins. Furthermore, the addition of taurine has no negative impact on culture performance or the quality of the resulting antibodies. The present invention provides a method for producing high-yield therapeutic protein comprising cultivating a recombinant cell line in a medium containing taurine, wherein the cell line comprises a stably integrated nucleic acid encoding the therapeutic protein. The present invention relates to a cell culture medium, which is serum-free and comprises approximately 0.1 mM to approximately 10 mM of taurine. The present invention relates to a cell culture medium, which is serum-free and comprises approximately 1 mM to approximately 10 mM of taurine. The present invention relates to a cell culture medium, which is serum-free and comprises approximately 1 mM to approximately 5 mM of taurine, approximately 1 mM to approximately 6 mM of taurine, approximately 1 mM to approximately 7 mM of taurine, approximately 1 mM to approximately 8 mM of taurine, or approximately 1 mM to approximately 9 mM of taurine. In some embodiments, the medium further comprises additional amino acids from the group consisting of arginine, histidine, lysine, aspartic acid, glutamic acid, serine, threonine, asparagine, glutamine, cysteine, glycine, proline, alanine, valine, isoleucine, leucine, methionine, phenylalanine, tyrosine, and tryptophan. In some embodiments, the medium contains <16 g / L of hydrolysate. In some embodiments, the medium contains no hydrolysate at all. In one embodiment, the medium contains a chemically defined base medium, such as a conventional formulation or a commercially available base medium. In another embodiment, the complete medium is chemically defined, serum-free, and hydrolysate-free. In some embodiments, the complete process, including the base medium and feeds, contains a total of at least 115 mM of a mixture of amino acids or amino acid salts. In one embodiment, the amino acid mixture comprises amino acids selected from the group consisting of arginine, histidine, lysine, aspartic acid, glutamic acid, serine, threonine, asparagine, glutamine, cysteine, glycine, proline, alanine, valine, isoleucine, leucine, methionine, phenylalanine, tyrosine, and tryptophan, in an amount selected from Table 1. In some embodiments, the medium contains one or more fatty acids. In one particular embodiment, the medium contains a mixture of fatty acids (or fatty acid derivatives) and alpha-tocopherol. The fatty acids or fatty acid derivatives are selected from the group consisting of linoleic acid, linolenic acid, thioctic acid, oleic acid, palmitic acid, stearic acid, arachidic acid, arachidonic acid, lauric acid, behenic acid, decanoic acid, dodecanoic acid, hexanoic acid, lignoceric acid, myristic acid, and octanoic acid. In some embodiments, the medium contains a mixture of nucleosides. In one embodiment, the medium contains adenosine, guanosine, cytidine, uridine, thymidine, and hypoxanthine. In some embodiments, the medium contains a mixture of salts. The salts include divalent cations, such as calcium and magnesium. In one embodiment, the medium contains calcium chloride and magnesium sulfate. Other salts may include phosphate salts. In one embodiment, the medium (1) contains 0.1 ± 0.015 mM, 1 ± 0.015 mM, 3 ± 0.05 mM, 5 ± 0.10 mM, 7 ± 0.15 mM, or 10 ± 0.2 mM of taurine, (2) contains ≤ 16 g / L of a hydrolysate, (3) is whey-free, (4) further optionally contains a mixture of amino acids, (5) contains a mixture of fatty acids, (6) contains a mixture of nucleosides including adenosine, guanosine, cytidine, uridine, thymidine, and hypoxanthine, and (7) contains calcium, magnesium, and phosphate salts. The present invention provides a method for producing a protein of interest in high yield, comprising cultivating a recombinant cell line in a cell culture medium containing at least approximately 0.1 mM to approximately 10 mM of taurine, wherein the cell line comprises a stably integrated nucleic acid encoding the protein. In other embodiments, the medium encompasses any of the aspects described above. mentioned in the invention. In another aspect, the invention provides a method for culturing eukaryotic cells for enhanced recombinant protein production, comprising the steps of: (a) propagating or maintaining the cells in a defined cell culture medium during the growth phase, (b) supplementing the base cell culture medium with approximately 0.1 mM to approximately 10 mM L-taurine and expressing a recombinant protein of interest during the production phase, and (c) increasing the titer of the protein of interest by adding taurine. In some embodiments, the taurine supplement is provided at least once during the production phase, or two, three, four, or five times during the production phase, or daily during the production phase. In other embodiments, the method further comprises supplementing the culture medium with approximately 0.1 mM to approximately 10 mM L-taurine during the growth phase.In some embodiments, the method provides improved recombinant protein production compared to eukaryotic cells lacking taurine supplementation, or with less than 0.1 mM taurine supplementation and under otherwise identical conditions. Yo In another aspect, the invention provides a method for culturing cells in a cell culture medium, such as any embodiment of the medium described in the aforementioned aspect. In one embodiment, the method employs the steps of propagating or maintaining a cell or cells in a medium that (1) contains taurine at a concentration of at least 0.1 mM ± 0.015 mM, (2) contains ≤ 16 g / L of hydrolysate, or does not contain hydrolysate, (3) is free of serum, and (4) optionally contains amino acids selected from the group consisting of a mixture of amino acids selected from Table 1. In one embodiment, the optional blend of amino acid supplements is selected from the group consisting of the amino acids in Table 1: Table 1 Amino Acid RANGE mM (mriol / L) RANGE (g / L) Alanine 0-11.2 0-1 Arginine 2.4-11.9 0.5-2.5 Asparagine 1.3-33.3 0.2-5 Aspartic Acid 1.5-93.9 0.2-12.5 Cysteine ​​1.1-19.9 0.2-3.5 Glutamic Acid 1.4-47.6 0.2-7 Glutamine 0-23.9 0-3.5 Glycine 0-16.7 0-1.25 Histidine 1-9.5 0.2-2 Isoleucine 1.5-22.9 0.2-3 Leucine 1.5-38.1 0.2-5 Urine 2.7-24.6 0.5-4.5 Metlonlna 1.3-13.4 0.2-2 Fenllalanlna 1.2-18.2 0.2-3 Prollna 1.7-26.1 0.2-3 Serlna 1.9-57.1 0.2-6 Threonlna 1.7-33.6 0.2-4 T rlpptophan 0.5-14.7 0.1-3 Tlroslna 0.9-22.2 0.2-5 Vallna 1.7-34.1 0.2-4 In some embodiments, the cell or cells are mammalian cells, avian cells, insect cells, yeast cells, or bacterial cells. In one embodiment, the cells are mammalian cells useful in the production of recombinant proteins, such as CHO cells or the CHO-K1 derivative. In some embodiments, the cells express a protein of interest, such as a biotherapeutic protein. The biotherapeutic protein may be an antigen-binding protein, which may contain an Fc domain. In some embodiments, the protein of interest is an Fc fusion protein, such as an ScFv molecule or a trap molecule. Trap molecules include, but are not limited to, the VEGF trap protein and IL-1 trap protein. In some embodiments, the protein of interest is an antibody, such as a human monoclonal antibody, a humanized monoclonal antibody, a bispecific antibody, or an antibody fragment. Given the positive effects on protein production by the inclusion of taurine in various forms of whey-free media, cells cultured according to this method result in an average increase in protein titer. In one embodiment, when compared to the protein titer in a medium not supplemented with taurine, cells cultured in taurine-supplemented culture according to this method produce proteins with a protein titer that is at least 8% higher than the titer of the comparator control culture (i.e., culture not supplemented with taurine). In one embodiment, cells cultured in taurine-supplemented culture, when compared to the protein titer in medium not supplemented with taurine, produce a protein titer that is at least 9%, at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, or at least 29% higher than the title of the control crop for comparison. Furthermore, the inclusion of taurine alone in serum-free medium results in cultured cells producing a lower ammonia byproduct than without taurine. In a serum-free and hydrolysate-free implementation of the medium supplemented with ts urine, the cell culture is able to achieve a reduction in the ammonia byproduct level (mM of NH3) that is at least 4% lower, and up to 32% lower, than a similar cell culture in a similar cell culture medium that does not contain any supplement (i.e., less than 0.1 mM of taurine or no taurine supplement). In another embodiment, the method includes the step of adding one or more place-in-use additions to the cell culture medium. In some embodiments, the place-in-use addition is any one or more of NaHCO3, glutamine, insulin, glucose, CuSO4, ZnSO4, FeCl3, NiSO4, Na4EDTA, and Na3 citrate. In one embodiment, the method employs the step of adding each of the following place-in-use chemicals to the cell culture medium: NaHCO3, glutamine, insulin, glucose, CuSO4, ZnSO4, FeCl3, NiSO4, Na4EDTA, and Na3 citrate. In some embodiments, the place-in-use additions may be included in the medium at the beginning. In one specific embodiment, the aspect provides a method for culturing cells in a serum-free medium consisting essentially of (1) taurine at a concentration of at least 0.1 mM; (2) contains £16 g / L of a hydrolysate, (3) is whey-free, and (4) optionally further contains at least approximately 20 mM, or at least approximately 25 mM, or at least approximately 30 mM, or at least approximately 40 mM, or at least approximately 50 mM, or at least approximately 60 mM, or at least approximately 70 mM total of an amino acid mixture selected from the group consisting of alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine. In another aspect, the invention provides a method for producing a protein of interest by employing the steps of (1) introducing into a cell a nucleic acid sequence encoding a protein of interest; (2) selecting a cell or cells expressing the protein of interest; (3) culturing the selected cell in an embodiment of the serum-free cell culture medium described in any preceding aspect or in accordance with any embodiment of the method described in the present invention; and (4) expressing the protein of Yo Interest in the cell where the protein of interest is secreted into the medium. In some embodiments, the cell used in the production of the protein is a mammalian cell capable of producing a biotherapeutic product, such as a CHO, 293, or BHK cell, or any of their derivatives. In one embodiment, the cell is a CHO cell, such as a CHO-K1 cell. In some embodiments, the protein of interest is an antigen-binding protein. In some embodiments, the protein of interest is a protein that has an Fc domain. In some cases, these two proteins of interest can overlap, such as in the case of an Fc-receptor fusion protein, an antibody, and an ScFv protein, for example. Therefore, in some embodiments, the protein of interest is an antibody, such as a human antibody or a humanized antibody, or an antibody fragment, such as a Fab or F(ab')2, a bispecific antibody, a trap molecule such as a VEGF Trap or an IL-1 Trap, an ScFv molecule, a soluble TCR-Fc fusion protein, or the like. In one embodiment, the protein of interest is capable of being produced in a The average titration of 14, 15, 16, or 17 days is at least 8% higher than the average titer of 14, 15, 16, or 17 days produced by a similar cell in a serum-free culture medium containing less than 0.1 mM or no taurine supplementation. In one embodiment, the protein of interest is capable of being produced at an average titration of 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17 days that is at least 9%, at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, or at least 29% higher than the average titer of 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17 days produced by a similar cell in a serum-free cell culture medium containing less than 0.1 mM or no taurine supplement. In another embodiment, the protein of interest is produced by (1) introducing into a CHO cell a nucleic acid sequence encoding a protein of interest, such as an antibody or other antigen-binding protein; (2) selecting a cell that stably expresses the protein of interest; (3) culturing the selected cell in a serum-free cell culture medium comprising approximately 0.1 mM to approximately 10 mM of taurine. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the protein titration (yield) of samples recovered each day of production culture in a cell culture producing Ab3, where taurine supplementation is provided (solid squares connected by solid lines) compared to no taurine supplementation (x connected by dashed lines). The benefits of taurine supplementation on protein yield can be observed as early as day 6 of production culture. DETAILED DESCRIPTION It should be understood that this invention is not limited to the particular methods and experimental conditions described, as these methods and conditions may vary. It should also be understood that the terminology used in the present invention is intended to describe particular embodiments only and is not meant to be a limitation, since the scope of the present invention is defined by the claims. As used in this specification and in the appended claims, the singular forms “a”, “an”, “the”, and “the” include plural references unless the context clearly indicates otherwise. Thus, for example, a reference to “a method” includes one or more methods and / or steps of the type described in the present invention and / or which will become evident to persons skilled in the art after reading this description. Unless otherwise defined, all technical and scientific terms employed in the present invention have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. Although any method and material similar or equivalent to those described herein may be used in the practice of the present invention, particular methods and materials are described below. All publications mentioned in the present invention are incorporated herein by reference in their entirety. The applicants have surprisingly discovered that adding taurine to a cell culture medium improves protein production by a recombinant cell in cell culture relative to a cell culture medium containing very little or no taurine. Before describing the present cell cultures and methods, it should be understood that this invention is not limited to the particular methods and experimental conditions described, since said methods and Conditions may vary. It should also be understood that the terminology employed in the present invention is intended to describe particular embodiments only, and is not intended to be limiting. The section headings used in the present invention are for organizational purposes only and should not be construed as limiting the scope of the invention. The methods and techniques described in the present invention are generally carried out in accordance with conventional methods known in the art and as described in various general and more specific references cited and described throughout this specification, unless otherwise indicated. See, for example, Sambrook et al., Molecular Cloning: A Laboratory Manual, 3rd ed., Coid Spring Harbor Laboratory Press, Coid Spring Harbor, NY (2001) and Ausubel et al., Current Protocols in Molecular Biology, Greene Publishing Associates (1992), Harlow and Lane, Antibodies: A Laboratory Manual, Coid Spring Harbor Laboratory Press, Coid Spring Harbor, NY (1990), and Julio E. Celis, Cell Biology: A Laboratory Handbook, 2nd ed., Academic Press, New York, NY (1998), and Dieffenbach and Dveksler, PCR Primer: A Laboratory Manual, Coid Spring Harbor Laboratory Press, Coid Spring Harbor, NY (1995). All publications mentioned throughout this description are incorporated herein by way of reference in their entirety. DEFINITIONS “Taurine” is also known as 2-aminoethanesulfonic acid (IUPAC nomenclature; CAS Registry No. 107-35-7). “Taurine” and “L-taurine” are used interchangeably to refer to the same organic compound. Taurine is an organic acid containing an amino group; however, it is not considered an “amino acid” in the traditional sense, as amino acids contain both an amino and a carboxyl group. Taurine biosynthesis occurs when hypotaurine, a cysteine ​​derivative, is converted to taurine by oxidation. The terms “supplementation,” “to supplement,” “supplemented with,” and similar terms refer to adding an ingredient, component, molecule, etc., that can be used in a cell culture medium to maintain and / or promote cell growth and / or differentiation, to extend or enhance an attribute of the culture or the cells as a whole, or to compensate for a deficiency. For this purpose, taurine supplementation involves adding taurine at a specific concentration to a solution within the culture medium. The terms peptide, polypeptide, and protein are used interchangeably throughout this invention and refer to a molecule comprising two or more amino acid residues linked together by a peptide bond. Peptides, polypeptides, and proteins may also include modifications such as glycosylation, lipid linkage, sulfation, gamma-carboxylation of glutamic acid residues, alkylation, hydroxylation, and ADP-bisylation. Peptides, polypeptides, and proteins may be of scientific or commercial interest, including protein-based drugs. Peptides, polypeptides, and proteins include, among other things, antibodies and chimeric or fusion proteins. Peptides, polypeptides, and proteins are produced using recombinant animal cell lines and cell culture methods. The term “heterologous polynucleotide sequence,” in this context, refers to nucleic acid polymers that encode proteins of interest, such as chimeric proteins (such as trap molecules), antibodies, or antibody fragments (e.g., VH, VL, CDR3) that are produced as a biopharmaceutical drug. The heterologous polynucleotide sequence can be manufactured using genetic engineering techniques (e.g., as a sequence encoding a chimeric protein, a codon-optimized sequence, an intron-free sequence, etc.) and introduced into the cell, where it may reside as an episome or integrate into the cell's genome. The heterologous polynucleotide sequence may be a naturally occurring sequence that is introduced into an ectopic site within the genome of the producing cell.The heterologous polypeptide sequence can be a naturally occurring presentation sequence from another organism, such as a sequence that encodes a human ortholog. The term "antibody" refers to an immunoglobulin molecule consisting of four polypeptide chains: two heavy chains (H) and two light chains (L) interconnected by disulfide bonds. Each heavy chain has a heavy chain variable region (HCVR or VH) and a heavy chain constant region. The heavy chain constant region contains three domains: CH1, CH2, and CH3. Each light chain has a light chain variable region and a light chain constant region. The light chain constant region consists of one domain (CL). The VH and VL regions may be further subdivided into hypervariability regions, called complementarity-determining regions (CDRs), interspersed with more conserved regions called structural regions (FRs).Each VH and VL is composed of three CDRs and four FRs, arranged from the amino terminus to the carboxy terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The term antibody includes reference to glycosylated and non-glycosylated immunoglobulins of any isotype or subclass. The term antibody includes antibody molecules prepared, expressed, created, or isolated by recombinant means, such as antibodies isolated from a host cell transfected to express the antibody. The term antibody further includes bispecific antibody, which includes a heterotetrameric immunoglobulin that can bind to more than one different epitope. Bispecific antibodies are generally described in U.S. Patent Application Publication No. 2010 / 0331527, which is incorporated herein by reference. The term antigen-binding portion of an antibody (or “antibody fragment”) refers to one or more fragments of an antibody that retain the ability to bind specifically to an antigen. Examples of binding fragments encompassed within the term antigen-binding portion of an antibody include (i) a Fab fragment, a monovalent fragment consisting of the VL, VH, CL, and CH1 domains; (ii) an F(ab')2 fragment, a bivalent fragment comprising two Fab fragments linked by a disulfide bridge in the hinge region; (iii) an Fd fragment consisting of the VH and CH1 domains; (v) an Fv fragment consisting of the VL and VH domains of a single antibody arm; (v) a dAb fragment (Ward et al.(1989) Nature 241:544546), which consists of a VH domain, (vi) an isolated CDR, and (vii) an scFv, which consists of the two domains of the Fv fragment, VL and VH, linked by a synthetic ligand to form a single protein chain in which the VL and VH regions pair to form monovalent molecules. Other forms of single-chain antibodies, such as diabodies, are also encompassed under the term “antibody” (see, for example, Holliger et al. (1993) PNAS USA 90:6444-6448; Poljak et al. (1994) Structure 2:1121-1123). Furthermore, an antibody or its antigen-binding portion can be part of a larger immunoadheslon molecule, formed by covalent or non-covalent association of the antibody or antibody portion with one or more other proteins or peptides. Examples of such immunoadheslon molecules include the use of the streptavidin core line to prepare a tetrameric scFv molecule (Kipriyanov et al. (1995) Human Antibodies and Hyperdomes 6:93-101) or the use of a cysteine ​​residue, a marker peptide, and a C-terminal polyhistidine tag to prepare bivalent, biotinylated scFv molecules (Kipriyanov et al. (1994) Mol. Immunol. 31:1047-1058). Antibody portions, such as Fab and F(ab')2 fragments, can be prepared from whole antibodies using conventional techniques, such as via papain or pepsin digestion of whole antibodies.Additionally, antibodies, antibody portions, and immunoadhesion molecules can be obtained using conventional recombinant DNA techniques commonly known in the field (see Sambrook et al., 1989). The term “human antibody” is intended to include antibodies having variable and constant regions derived from human germline immunoglobulin sequences. The human antibodies of the invention may include amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo), for example, in CDRs and in particular CDR3. However, the term “human antibody,” in the present context, is not intended to include antibodies in which CDR sequences derived from the germline of another mammalian species, such as a mouse, have been grafted onto human structural sequences. The term recombinant human antibody, in the present context, is intended to include all human antibodies that are prepared, expressed, created, or isolated by recombinant means, such as antibodies expressed using a recombinant expression vector transfected into a host cell, antibodies isolated from a recombinant human antibody library, combination antibodies, antibodies isolated from an animal (e.g., a mouse) that is transgenic for human immunoglobulin genes (see, e.g., Taylor et al. (1992) Nuci. Acids Res. 20:6287-6295), or antibodies prepared, expressed, created, or isolated by any other means involving the splicing of human immunoglobulin gene sequences into other DNA sequences. Such recombinant human antibodies have variable and constant regions derived from human germline immunoglobulin sequences.In certain embodiments, however, such recombinant human antibodies are subjected to in vitro mutagenesis (or, when a transgenic animal is used for human Ig sequences, in vivo somatic mutagenesis) and therefore the amino acid sequences of the VH and VL regions of recombinant antibodies are sequences that, although derived from and related to human germline VH and VL sequences, may not exist naturally within the in vivo human antibody germline repertoire. “Fc fusion proteins” comprise part or all of two or more proteins, one of which is an Fc portion of an immunoglobulin molecule, that are not otherwise found together in nature. The preparation of fusion proteins comprising certain heterologous polypeptides fused to various portions of antibody-derived polypeptides (including the Fc domain) has been described, for example, by Ashkenazi et al., Proc. Nati. Acad. ScL USA 88: 10535, 1991; Byrn et al., Nature 344:677, 1990; and Hollenbaugh et al., Construction of Immunoglobulin Fusion Proteins, in Current Protocols in Immunology, Suppl. 4, pages 10.19.1-10.19.11, 1992. “Fc-receptor fusion proteins” comprise one or more extracellular domains of a receptor coupled to an Fc residue, which in some embodiments comprises a hinge region followed by a CH2 and CH3 domain of an immunoglobulin. In some embodiments, the Fc-receptor fusion protein contains two or more distinct receptor chains that bind to one or more ligands. For example, an Fe fusion protein is a trap, such as an IL-1 trap (e.g., rilonacept, which contains the IL-1RAcP ligand-binding region fused to the Fe-fused extracellular IL-1R1 region of hlgG1; see U.S. Pat. No. 6,927,004), or a VEGF trap (e.g., aflibercept, which contains the Ig domain 2 of the VEGF receptor Flt1 fused to the Ig domain 3 of the Fe-fused VEGF receptor Flk1 of hlgG1; see U.S. Pat. Nos. 7,087,411 and 7,279,159). CELL CULTUREThe terms cell culture medium and culture medium refer to a nutrient solution used to grow mammalian cells that typically provides the nutrients necessary to promote cell growth, such as a carbohydrate energy source, essential amino acids (e.g., phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine) and non-essential amino acids (e.g., alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine), trace elements, energy sources, lipids, vitamins, etc. Cell culture medium may contain extracts, e.g., serum or peptones (hydrolysates), which supply raw materials that support cell growth. Media may contain soy extracts or yeast derivatives instead of animal-derived extracts.A chemically defined medium refers to a cell culture medium in which all chemical components are known (i.e., have a known chemical structure). A chemically defined medium is entirely free of animal-derived components, such as animal-derived peptones or serum. In one embodiment, the medium is a chemically defined medium. The solution may also contain components that enhance growth and / or survival above the minimum threshold, including hormones and growth factors. The solution is preferably formulated at an optimal pH and salt concentration for cell survival and proliferation. A “cell line” refers to a cell or cells that are derived from a particular lineage through serial passage or subculture of cells. The term “cells” is used interchangeably with “cell population.” The term “cell” includes any cell that is suitable for expressing a recombinant nucleic acid sequence. Cells include those of eukaryotes, such as non-human animal cells, mammalian cells, human cells, avian cells, insect cells, yeast cells, or cell fusions such as, for example, hydroidomas or quadroidomas. In certain embodiments, the cell is a human, mouse, monkey, hamster, rat, or mouse cell. In other embodiments, the cell is selected from the following cells: CHO (e.g., CHO K1, DXB-11 CHO, Veggle-CHO), COS (e.g., COS-7), retinal cell, Vero, CV1, kidney (e.g., HEK293, 293 EBNA, MSR 293, MDCK, HaK, BHK21), HeLa, HepG2, WI38, MRC 5, Colo25, HB 8065, HL60, lymphocyte, e.g., Jurkat (T lymphocyte) or Daudl (B lymphocyte), A431 (epidermal), CV-1, U937, 3T3, L cell, C127 cell, SP2 / 0, NS-0, MMT cell, stem cell, tumor cell, and a cell line derived from a cell mentioned above.In some embodiments, the cell comprises one or more viral genes, e.g., a retinal cell expressing a viral gene (e.g., a PER.C6® cell). In some embodiments, the cell is a CHO cell. In other embodiments, the cell is a CHO K1 cell. to a sowing crop where it is used for protein production and One aspect of the invention relates to expanding a cell population with antenna collection in production culture. Taurine can be added to the base medium in a seed culture formulation, according to the invention as described in the present invention. Another aspect of the invention relates to a production culture in which protein is produced and harvested. Prior to the production phase, there is generally a growth phase (also known as a "seed train" or seeding culture) where all the components for cell culture are supplied to the culture vessel at the beginning of the culture process, and then the cell population is expanded until it is ready for production scale. As such, the culture vessel is inoculated with cells at an appropriate seeding density for the initial cell growth phase, depending on the starting cell line. In some aspects, taurine can be added to the basal culture medium in a seeding culture formulation, according to the invention as described herein, in order to further improve or increase cell productivity in the subsequent production phase.The cell culture can be inoculated with cells at a cell density of approximately 0.8 x 10⁶ cells / mL to approximately 5 x 10⁶ cells / mL. In other embodiments, the cells in the cell cultures can reach a specified concentration of viable cells prior to transfer to the production phase (i.e., transfer VCC, for example, between approximately 3 x 10⁶ cells / mL and approximately 2 x 10⁷ cells / mL). One aspect of the invention relates to a production culture system where cell culture conditions are modified to enhance the growth of recombinant eukaryotic cells while simultaneously improving the production of one or more recombinant proteins of interest by said cells and maintaining cell viability, particularly by adding taurine to the production culture medium and / or the Seed Train cell culture. In the production culture vessel or bioreactor, a basal culture medium and cells are supplied to a culture vessel following a seeding or growth phase. In certain embodiments, the cell supernatant or cell lysate is collected at or around the peak cell density.In some embodiments, the peak cell density of the production cell culture occurs at approximately 15 to approximately 45 x 10⁶ cells / mL. In other embodiments, the polypeptide or protein of interest is recovered from the culture medium or cell lysate, as appropriate, depending on the location of the protein of interest, using well-established techniques. Culture vessels include, but are not limited to, well plates, T-flasks, shaker flasks, shaken vessels, centrifuge flasks, hollow fiber, airlift bioreactors, and similar devices. A suitable cell culture vessel is a bioreactor. A bioreactor refers to any A culture vessel is a manufactured or constructed vessel designed to manipulate or control environmental conditions. Such culture vessels are well known in the art. Bioreactor processes and systems have been developed to optimize gas exchange, provide sufficient oxygen to support cell growth and productivity, and remove CO2. Maintaining efficient gas exchange is a key criterion for successfully scaling up cell culture and protein production. Such systems are well-known to those skilled in the art. In the polypeptide production phase, a fed-batch cell culture refers to a batch culture where animal cells and culture medium are initially supplied to the culture vessel, and additional culture nutrients are slowly introduced, continuously or in discrete increments, to the culture during cultivation, with or without periodic harvesting of cells and / or product before the end of the culture. Fed-batch culture includes semi-continuous fed-batch culture where the entire culture (which may include cells and medium) is periodically removed and replaced with fresh medium.Fed-batch culture differs from simple batch culture in that all components for cell culture (including animal cells and all culture nutrients) are supplied to the culture vessel at the beginning of the process. Fed-batch culture is further distinguished from perfusion culture in that the supernatant is not removed from the culture vessel during the process, whereas in perfusion culture, cells are retained in the culture by, for example, filtration, and the culture medium is introduced continuously or intermittently and withdrawn from the culture vessel. However, sample removal for testing purposes is permitted in fed-batch cell culture. The fed-batch process continues until the maximum working volume and / or protein production has been reached. The phrase “continuous cell culture,” as used in the present invention, refers to a technique used to cultivate cells continuously, generally in a particular growth phase. For example, if a constant supply of cells is required, or if the production of a particular polypeptide or protein of interest is desired, the cell culture may need to be maintained in a particular growth phase. Therefore, the conditions must be continuously monitored and adjusted accordingly to maintain the cells in that particular phase. HALF The present invention provides a serum-free cell culture medium comprising approximately 0.1 mM to 10 mM of taurine. "Serum-free" refers to a cell culture medium that does not contain animal sera, such as fetal bovine serum. The serum-free medium may contain ≤ 16 g / L of hydrolysates, such as soybean hydrolysate. The present invention further provides a chemically defined medium that is not only serum-free but also hydrolysate-free. "Hydrolysate-free" refers to a cell culture medium that does not contain exogenous protein hydrolysates, such as animal or vegetable protein hydrolysates, such as peptones, tryptones, and the like. "Base medium" is the initial medium (present in Seed Train cell cultures and / or on day 0 of cell culture production) in which the cells are propagated and contains all the necessary nutrients, including a base mixture of amino acids.Various recipes (i.e., formulations) for base medium are commercially available. Similarly, "base feeding medium" contains mixtures of supplemental nutrients commonly consumed during a production culture and used in a feeding strategy (for a culture termed "batch fed"). A variety of base feeding media are commercially available. A "feed" includes scheduled additions to media at regular intervals, such as according to a protocol, including a continuous feeding culture system, such as in a chemostat (see C. Altamirano et al., Biotechnol Prog. 2001 Nov-Dec; 17(6):1032-41), or according to a batch fed process (YM). Huang et al., Biotechnol Prog. 2010 Sep-Oct;26(5): 1400-10). For example, a culture can be fed once a day, every other day, every three days, or it can be fed when the concentration of a specific medium component, which is being monitored, falls outside a desired range. Removing whey and reducing or eliminating hydrolysates from cell culture media, while simultaneously reducing batch-to-batch variability and increasing downstream processing steps, unfortunately decreases cell growth, viability, and protein expression. Therefore, chemically defined whey-free media with low or no hydrolysate content requires additional ingredients to enhance cell growth and protein production. Accordingly, the cell culture medium of the Invention comprises a base medium containing all the nutrients necessary for viable cell culture. Taurine may be added to the base medium in a seeding culture formulation, according to the Invention as described herein. Additionally, taurine may be added to the base medium in a production culture formulation, which can then be fed periodically (as in so-called "fed-batch" cultures) with or without additional ingredients such as pellets or increased concentrations of components such as amino acids, salts, sugars, vitamins, hormones, growth factors, buffers, antibiotics, lipids, trace elements, and the like, depending on the requirements of the cells to be cultured or the desired cell culture parameters. The invention provides that the cell culture medium supplemented with taurine can be depleted of amino acids during the course of protein production culture, where no additional amino acid supplementation is provided, or the cell culture medium supplemented with taurine can be "undepleted," where amino acid supplementation is provided to replace the depleted amino acids (as described below). The inventors have observed that supplementing cultures with taurine during the production phase improves recombinant protein production under various conditions. I of cultivation as described above. The invention provides a taurine supplemental medium which contains taurine in a concentration (expressed in millimoles per liter) of at least approximately 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 mM. In one embodiment, the medium additionally contains 100 pM ± 15 μM of ornithine, or 300 pM ± 45 pM of ornithine, or 600 pM ± 90 pM of ornithine, or even 900 pM ± 135 pM of ornithine. In another embodiment, the medium contains at least approximately 5 mg / L ± 1 mg / L of ornithine · HCI, or at least approximately 10 mg / L ± 2 mg / L of ornithine · HCI, 15 mg / L ± 2.25 mg / L of ornithine · HCI, or at least approximately 50 mg / L ± 7.5 mg / L of ornithine · HCI, or at least approximately 100 mg / L ± 15 mg / L of ornithine · HCI, or at least approximately 150 mg / L ± 22.5 mg / L of ornithine · HCI. Putrescine may be optionally added to the supplemental medium. Putrescine has been included, in very low concentrations, as a component in some cell culture medium formulations; see, for example, WO 2005 / 028626, which describes 0.02–0.08 mg / L of putrescine; U.S. Patent No. 5,426,699 (0.08 mg / L); U.S. Patent No. RE30,985 (0.16 mg / L); U.S. Patent No. 5,811,299 (0.27 mg / L); U.S. Patent No. 5,122,469 (0.5635 mg / L); U.S. Patent No. 5,063,157 (1 mg / L); WO 2008 / 154014 (–100 pM–1000 pM). Pat's request. US No. 2007 / 0212770 (0.5 - 30 mg / L polyamine; 2 mg / L putrescine; 2 mg / L putrescine + 2 mg / L ornithine; 2 mg / L putrescine + 10 mg / L ornithine). In some embodiments, the medium is additionally supplemented with a combination of ornithine and putrescine, where the putrescine may be at a concentration of at least approximately 150 to 720 μM. In some embodiments, the medium is additionally supplemented with putrescine at a concentration of approximately 170 to 230 μM. In one embodiment, the medium contains 200 μM ± 30 μM of putrescine in addition to 90 μM ± 15 μM of ornithine. In another embodiment, the medium contains 30 mg / L ± 4.5 mg / L of putrescine · 2HCl in addition to 15 mg / L ± 2.25 mg / L of ornithine. In another embodiment, the medium contains 30 mg / L ± 4.5 mg / L of putrescine · 2HCl in addition to 15 mg / L ± 2.25 mg / L of ornithine · HCl. (See International Publication No. WO2014 / 144198A1, published on September 18, 2014, which is incorporated herein by reference in its entirety). In still other embodiments, ornithine is present in the medium at a concentration ranging from 0.09 ± 0.014 mM to 0.9 ± 0.14 mM, such as 0.09 + 0.9 ± 0.14 mM of ornithine. In some, at least 0.20 ± 0.03 mM of additional putrescine is present. In some embodiments, the medium also contains putrescine. In some embodiments, the concentration ranges from 0.20 ± 0.03 mM to 0.714 ± 0.11 mM, such as 0.20 ± 0.03 mM, 0.35 ± 0.06 mM, or 0.714 ± 0.11 mM. Various other supplements may be added to the culture medium, and the expert in the technique will be able to determine the additionally appropriate conditions. In some embodiments, the medium is supplemented with a mixture of amino acids selected from the group consisting of aspartic acid, glycine, glutamic acid, lysine, phenylalanine, proline, serine, threonine, valine, arginine, histidine, asparagine, glutamine, alanine, isoleucine, leucine, methionine, tyrosine, and tryptophan, in order to prevent depletion as supplemental nutrients are required. In one embodiment, the medium is further supplemented with approximately 170 pM to 175 μM of nucleosides. In another embodiment, the medium contains purine derivatives at a cumulative concentration of at least 40 pM, at least 45 pM, at least 50 pM, at least 55 pM, at least 60 pM, at least 65 pM, at least 70 pM, at least 75 pM, at least 80 pM, at least 85 pM, at least 90 pM, at least 95 pM, at least 100 pM, or at least 105 pM. In yet another embodiment, the medium contains approximately 100 pM to 110 pM of purine derivatives. The purine derivatives include hypoxanthine and the nucleosides adenosine and guanosine. In one embodiment, the medium contains pyrimidine derivatives in a cumulative concentration of at least 30 pM, at least 35 pM, at least 40 pM, at least 45 pM, at least 50 pM, at least 55 pM, at least 60 pM, or at least 65 pM.In one embodiment, the medium contains approximately 65 pM to 75 pM of pyrimidine derivatives. Pyrimidine derivatives include the nucleosides thymidine, uridine, and cytidine. In one particular embodiment, the medium contains adenosine, guanosine, cytidine, uridine, thymidine, and hypoxanthine. In addition to the inclusion of any of the aforementioned additives, in one embodiment, the medium is further supplemented with micromolar amounts of fatty acids (or fatty acid derivatives) and tocopherol. In one embodiment, the fatty acids include any or more of linoleic acid, linolenic acid, thioctic acid, oleic acid, palmitic acid, stearic acid, arachidic acid, arachidonic acid, lauric acid, behenic acid, decanoic acid, dodecanoic acid, hexanoic acid, lignoceric acid, myristic acid, and octanoic acid. In one embodiment, the medium contains tocopherol, linoleic acid, and thioctic acid. In one realization, the medium can also be additionally Yo I supplemented with a vitamin mixture, which includes other essential nutrients, at a cumulative concentration of at least approximately 700 μM or at least approximately 2 mM. In one embodiment, the vitamin mixture contains one or more of D-biotin, choline chloride, folic acid, myo-inositol, niacinamide, pyridoxine HCl, D-pantothenic acid (hemiCa), riboflavin, thiamine HCl, vitamin B12, and the like. In one embodiment, the vitamin mixture includes the complete set of D-biotin, choline chloride, folic acid, myo-inositol, niacinamide, pyridoxine HCl, D-pantothenic acid (hemiCa), riboflavin, thiamine HCl, and vitamin B12. Various embodiments of the medium of the invention include any combination of the embodiments described above, including a chemically defined, hydrolysate-free, whey-free medium comprising taurine in the indicated amounts, plus inter alia (a) amino acids; (b) optionally nucleosides; (c) salts of divalent cations; (d) fatty acids and tocopherol; and (e) vitamins. In some embodiments, all small amounts of hydrolysates may be added to the taurine-supplemented medium. The applicants contemplate that in the practice of this invention, any or more of a variety of base medium or combinations thereof, in which taurine may be used, may be used. In general, the base media are known in the art and include, among others, Eagle's MEME (Minimum Essential Medium) (Eagle, Science, 1955, 112(3168):501-504), Harn's F12 (Ham, Proc. Nati. Acad. Sel. USA, 1965, 53:288-293), F-12 K medium, Dulbecco's medium, Dulbecco's Modified Eagle Medium (Proc. Nati. Acad. Sel. USA., 1952 Aug; 38(8): 747-752), DMEM / Ham's F12 1:1, Trowell's T8, A2 medium Holmes and Wolf, Biophys. Biochem. Cytol., 1961, 10:389-401), Waymouth medium (Davidson and Waymouth, Biochem. J., 1945, 39(2):188-199), Williams E medium (William's et al., Exp. Cell Res., 1971, 69:105 et seq.), RPMI 1640 (Moore et al., J. Amer. Med. Assoc., 1967, 199:519-524), 5 MCDB 104 / 110 medium (Bettger et al., Proc. Nati. Acad. Sci. USA, 1981, 78(9):55885592), Ventrex HL-1 medium, albumin-globulin medium (Orr et al., Appl. Microbiol., 1973, 25(1):49-54), RPMI-1640 medium, RPMI-1641 medium, Iscove Modified Dulbecco Medium, McCoy's 5 A medium, Leibovitz's L-15 medium, and serum-free medium such as EX-CELL™ 300 Series (JRH Biosciences, Lenexa, Kansas), protamine-zinc-insulin medium (Weiss et al., 1974, US 4,072,565), biotin-folate medium (Cartaya, 1978, US Re30,985), fatty acid transferrin medium (Baker, 1982, US 4,560,655), transferrin-EGF medium (Hasegawa, 1982, US 4,615,977; Chessebeuf, 1984, US 4,786).599), and other permutations of means (see Inlow, US 6,048,728; Drapeau, US 7,294,484; Mather, US 5,122,469; Furukawa, US 5,976,833; Chen, US 6,180,401; Chen, US 5,856,179; Etcheverry, US 5,705,364; Etcheverry, US 7,666,416; Ryll, US 6,528,286; Singh, US 6,924,124; Luán, US 7,429,491; and the like). In a particular embodiment, the medium is chemically defined and contains in addition to taurine: mixtures of amino acids as defined in the present invention, CaCl2 2H2O; HEPES buffer, KCl; MgSO4; NaCl; Na2HPO4 or other phosphate salts; pyruvate; D-biotin; choline chloride; folic acid; myo-inositol; niacinamide; pyridoxine HCl; D-pantothenic acid; riboflavin; thiamine HCl; vitamin B12; p-aminobenzoic acid; ethanolamine HCl; poloxamer 188; DL-α-tocopherol phosphate; linoleic acid; optionally adenosine; guanosine; cytid 2Na. eC>3; thioctic acid; and glucose; and ina; uridine; thymidine; and hypoxanthine In one embodiment, the starting osmolarity of the medium of the invention is 200-500, 250-400, 275-350, or approximately 300 mOsm. During cell growth in the medium of the invention, and particularly after any feeding according to a fed-batch protocol, the osmolarity of the culture can increase to approximately 350, 400, 450, 500, or up to approximately 550 mOsm. In some embodiments where the osmolarity of the defined medium is less than approximately 300, the osmolarity is brought to approximately 300 by adding one or more salts in excess of the specified amount. In one embodiment, the osmolarity is increased to a desired level by adding one or more of an osmolyte selected from sodium chloride, potassium chloride, a magnesium salt, a calcium salt, an amino acid salt, a fatty acid salt, sodium bicarbonate, sodium carbonate, potassium carbonate, a chelating agent that is a salt, a sugar (e.g., galactose, glucose, sucrose, fructose, fucose, etc.), and a combination thereof. In one embodiment, it is I add the osmolyte above its concentration in a component already present in the defined medium (e.g., a sugar is added above the specified concentration for a sugar component). Each of the previously described formulations of the medium, as well as any other serum-free medium containing at least approximately 0.1 mM taurine, is referred to as taurine-supplemented medium. Conversely, media that do not contain taurine, or media containing less than 0.1 mM taurine, are referred to hereafter as non-taurine-supplemented media. FED-BATCH CULTIVATION Feeding strategies for cell culture aim to ensure optimal cell growth and propagation outside of a multicellular organism or tissue. The appropriate culture conditions for mammalian cells are well-established in the field. See, for example, Animal cell culture: A Practical Approach, D. Rickwood, ed., Oxford University Press, New York (1992). Mammalian cells can be cultured in suspension or while attached to a solid substrate. Fluidized bed bioreactors, hollow fiber bioreactors, roller flasks, shaker flasks, or stirred tank bioreactors, with or without microcarriers, and operated in batch, fed-batch, continuous, or i modes Semi-continuous or perfusion methods are available for mammalian cell culture. The cell culture medium or concentrated feeding medium can be added to the culture continuously or at intervals during the culture period. For example, a culture can be fed once a day, every other day, every three days, or when the concentration of a specific component of the medium, which is being monitored, falls outside a desired range. In addition to the inclusion of taurine, in one embodiment, the medium may be further supplemented with amino acids at a cumulative (total) concentration of at least 20 mM. In one embodiment, the initial amino acid concentration included in the starting cell culture medium is not included in said cumulative (total) concentration of supplemented amino acids.In one embodiment of the cell culture medium, or in the method for culturing cells or the method for producing a protein of interest, the medium may be supplemented in an amount greater than approximately 20 mM, greater than approximately 25 mM, greater than approximately 30 mM, greater than approximately 40 mM, greater than approximately 50 mM, or greater than approximately 60 mM, greater than approximately 70 mM, greater than approximately 100 mM, greater than approximately 200 mM, greater than approximately 300 mM, greater than approximately 400 mM, or greater than approximately 500 mM. See also Table 1 of the present invention. In one embodiment, the amount of amino acids added to the medium is approximately 30 mM ± 10 mM or more. Supplementation feeding regimens can be optimized by technical experts to aid cell growth, minimize cell stress, or to provide an "undepleted medium" during the production phase. I "Undepleted medium" refers to cell culture medium that has been determined to contain the nutrients, particularly the amino acids, necessary for the production of a recombinant protein of interest. Generally, amino acid feeds supplement the amino acids required as building blocks for producing a recombinant protein in cell culture. However, some amino acids may be depleted more rapidly than others depending on the requirements of the particular protein produced by the cultured cells. In undepleted medium, the feeding regimen has been determined so that the necessary amino acids are replenished as they are consumed.Therefore, depletion and subsequently optimal consumption rates (pg / cell-day) can be determined by the following steps: culture eukaryotic cell(s) expressing the protein of interest in a cell culture medium; measure each amino acid concentration in the culture medium at points in time to establish a depletion level; identify the depletion time point at which the amino acid concentration falls below the depletion level; calculate the consumption rates for each amino acid; and determine the optimal consumption rate as the consumption rate at the time point immediately preceding the depletion time point. The cell culture is then supplemented with an appropriate concentration of a particular amino acid to maintain these optimal consumption rates as determined, so as not to deplete the culture medium. The present invention is understood to provide a cell culture medium supplemented with taurine that improves the protein titer in depleted as well as non-depleted cultures. The present invention provides a cell culture comprising a cell line expressing a protein of interest in a taurine-supplemented medium as described above. Examples of cell lines routinely used to produce protein biotherapeutic agents include, among others, primary cells, BSC cells, HeLa cells, HepG2 cells, LLC-MK cells, CV-1 cells, COS cells, VERO cells, MDBK cells, MDCK cells, CRFK cells, RAF cells, RK cells, TCMK-1 cells, LLCPK cells, PK15 cells, LLC-RK cells, MDOK cells, BHK cells, BHK15 cells, CHO cells, CHO-K1 cells, NS-1 cells, MRC-5 cells, WI-38 cells, 3T3 cells, 293 cells, PerC6 cells, and chicken embryo cells. In one embodiment, the cell line is a CHO cell line or one or more of several specific CHO cell variants optimized for large-scale protein production, e.g., CHO-K1. In one embodiment, the taurine-supplemented cell culture contains insulin, which can be added as an ingredient at the point of use to the medium, or can be included in the medium formulation. In one embodiment, the line Cellular I comprises cells capable of producing a biotherapeutic protein. In one embodiment, the medium is supplemented at intervals during cell culture according to a fed-batch process. Fed-batch culture is generally known in the art and employed to optimize protein production (see YM Huang et al., Biotechnol Prog. 2010 SepOct;26(5): 1400-10). The cell growth or seeding culture phase (i.e., an initial cell culture), where no medium exchange is provided, is typically followed by a second, distinct culture, known as the polypeptide production phase. Fed-batch processes are typically used during the production phase. The invention provides a cell culture medium comprising approximately 0.1 mM to approximately 10 mM of taurine at the beginning of the production cell culture (day 0). Alternatively, the cell culture medium comprising approximately 0.1 mM to approximately 10 mM of taurine can be supplemented on days 1, 2, 3, 4, 5, 6, 7, 8, 9, and / or 10 of the production cell culture. The cell culture medium added to the production culture on multiple days comprises a total amount of taurine between approximately 0.1 mM and approximately 10 mM. The cell culture medium comprising total taurine between approximately 0.1 mM and approximately 10 mM can be added in any consecutive manner. Taurine can also be supplemented in the basal medium during the expansion phase of Seed Train cell cultures. Supplemental feeding, including additional nutrients such as vitamins, amino acids, and other nutrients as previously described in this invention, can be carried out at intervals at a frequency of daily or every 2-3 days during the production crop period. Supplemental feeding (supplemented medium containing added nutrients) can be performed at least twice, or at least eight times, during the production crop period of two weeks or more. In another embodiment, supplemental feeding could be performed daily during the crop period. Alternative crop feeding plans are also contemplated. Additional amino acid supplementation can also be carried out to provide a non-depleted medium, where the depleted amino acids are determined according to methods known in the art and described in the present invention. When this regime is employed, the additional amino acids are supplemented or added at intervals, preferably daily, or every 2-3 days, for the duration of the production culture, depending on the determination of amino acid depletion. In one embodiment, the additional amino acid mixture is added to the culture to maintain an undepleted cell culture medium on or around day 1, day 2, day 3, day 4, day 5, day 6, day 7, day 8, day 9, or around that day, day 10 or around that day, day 11 or around that day, day 12 or around that day, day 13 or around that day, and day 14 or around that day, during a crop of 2 weeks or more. Alternative crop feeding plans are also considered. Animal cells, such as CHO cells, can be cultured in small-scale cultures, such as in 125 mL containers with approximately 25 mL of medium, 250 mL containers with approximately 50 to 100 mL of medium, and 500 mL containers with approximately 100 to 200 mL of medium. Alternatively, cultures can be grown on a large scale, such as by For example, 1000 mL containers that hold approximately 300 to 1000 mL of medium, 3000 mL containers that hold approximately 500 mL to 3000 mL of medium, 8000 mL containers that hold approximately 2000 mL to 8000 mL of medium, and 15000 mL containers that hold approximately 4000 mL to 15,000 mL of medium. Cultures for manufacturing may contain 10,000 L of medium or more. Large-scale cell cultures, such as those used for the clinical manufacture of protein-based therapeutic agents, are typically maintained for days or even weeks while the cells produce the desired protein or proteins. During this time, the culture can be supplemented with a concentrated feeding medium containing components such as nutrients and amino acids, which are consumed during the course of the culture. The concentrated feeding medium can be based on any cell culture medium formulation.This type of concentrated feeding medium can contain most of the components of the cell culture medium at, for example, approximately 5, 6, 7, 8, 9, 10, 12, 14, 16, 20, 30, 50, 100, 200, 400, 600, 800, or even approximately 1000 times their normal usable amount. Concentrated feeding media are often used in fed-batch culture processes. In some embodiments, the taurine-containing cell culture is further supplemented with "site-of-use additions," also known as admixtures, site-of-use ingredients, or site-of-use chemicals, during the course of cell growth or protein production. Site-of-use additions include any one or more of a growth factor or other proteins, a buffer, an energy source, a salt, an amino acid, a metal, and a chelating agent. Other proteins include transferrin and albumin. Growth factors, which include cytokines and chemokines, are generally known in the art and are known to stimulate cell growth, or in some cases, cell differentiation. A growth factor is usually a protein (e.g., insulin), a small peptide, or a steroid hormone, such as estrogen, DHEA, testosterone, and the like. In some cases,A growth factor can be a non-natural chemical that promotes cell proliferation or protein production, such as tetrahydrofolate (THF), methotrexate, and similar substances. Non-limiting examples of protein and peptide growth factors include anglopoietins, bone morphogenetic proteins (BMPs), brain-derived neurotrophic factor (BDNF), epidermal growth factor (EGF), erythropoietin (EPO), fibroblast growth factor (FGF), glial cell line-derived neurotrophic factor (GDNF), granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), and growth differentiation factor 9 (GDF9).hepatocyte growth factor (HGF), hepatoma-derived growth factor (HDGF), insulin, insulin-like growth factor (IGF), migration-stimulating factor, mylostatin (GDF-8), nerve growth factor (NGF) and other neurotrophins, platelet-derived growth factor (PDGF), thrombopoietin (TPO), transforming growth factor alpha (TGF-α), transforming growth factor beta (TGF-β), tumor necrosis factor alpha (TNF-α), vascular endothelial growth factor (VEGF), Wnt signaling pathway agonists, placental growth factor (PIGF), fetal bovine somatotropin (FBS), interleukin-1 (IL-1), IL-2,IL-3, IL-4, IL-5, IL-6, IL-7, and similar factors. In one embodiment, the cell culture medium is supplemented with the growth factor Insulin at the point of use. In one embodiment, the concentration of insulin in the medium, i.e., the amount of insulin in the cell culture medium after addition, is approximately 0.1 μM to 10 μM. Buffers are generally known in the art. The invention is not restricted to any particular buffer or buffers, and anyone with ordinary knowledge of the art can select a buffer or buffer system suitable for use with a particular cell line that produces a particular protein. In one embodiment, a site-addition buffer is NaHCO3. In another embodiment, the buffer is HEPES. In other embodiments, the site-addition buffer comprises both NaHCO3 and HEPES. The energy sources for use as an in-place addition in cell culture are also well known in the art. Without limitation, in one embodiment, the in-place addition energy source is glucose. Given the particular and specific requirements of a particular cell line and the protein to be produced, in one embodiment glucose can be added to the medium at a concentration of approximately 1 to 20 mM. In some cases, glucose can be added at elevated levels of 20 g / L or higher. Chelating agents are also well known in cell culture and protein production techniques. Anhydrous tetrasodium EDTA and citrate are two common chelating agents used in this technique, although other chelating agents may be employed in the practice of this invention. In one embodiment, the point-of-use chelating agent is tetrasodium EDTA dihydrate. In another embodiment, the point-of-use chelating agent is citrate, such as Na3C6H5O7. In one embodiment, the cell culture medium may be further supplemented with one or more site-added amino acids as an energy source, such as glutamine. In one embodiment, the cell culture medium is supplemented with site-added glutamine to a final concentration of approximately 1 mM to 13 mM. Other additions at the point of use include one or more of various metal salts, such as iron, nickel, zinc, and copper salts. In one embodiment, the cell culture medium is supplemented with any one or more of copper sulfate, zinc sulfate, ferric chloride, and nickel sulfate. In some embodiments, the protein titer produced from cell culture in taurine-supplemented medium is at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22% higher, at least 23% higher, at least 24% higher, at least 25% higher, at least 26% higher, at least 27% higher, at least 28% higher, or at least 29% higher than the protein titer (yield) of cells grown without taurine supplementation.In some embodiments, the protein titer produced from cells in taurine-supplemented medium is at least 2%, at least 3%, at least 4%, or at least 5% higher than the protein titer (yield) of similar or identical cells grown in non-taurine-supplemented medium. In some realizations, the accumulation of ammonia in the cell culture is decreased by more than 4%, more than 5%, more than 6%, more than 7%, more than 8%, more than 9%, more than 10%, more than 15%, or more than 20% in taurine-supplemented medium compared to cell culture in non-taurine-supplemented medium. PROTEIN PRODUCTION In addition to the taurine-supplemented medium and the methods for culturing cells in taurine-supplemented medium, the present invention provides I. Improved methods for producing a protein, such as a therapeutically effective antibody or other biopharmaceutical drug substance, in a cell cultured in a taurine-supplemented medium. The present invention provides a method for producing a therapeutic protein with high yield comprising culturing a recombinant cell line in a taurine-containing medium, wherein the cell line comprises a stably integrated nucleic acid encoding the therapeutic protein. In some embodiments, the protein titer (yield) by mammalian cells grown in medium containing taurine (taurine-supplemented medium) is at least 100 mg / L, at least 0.5 g / L, at least 1 g / L, at least 1.2 g / L, at least 1.4 g / L, at least 1.6 g / L, at least 1.8 g / L, at least 2 g / L, at least 2.5 g / L greater than the protein titer by an identical mammalian cell grown in medium not supplemented with taurine. In some embodiments, the protein yield or titer, which can be expressed in grams of protein product per liter of culture medium, from cells grown in medium supplemented with taurine is at least 100 mg / L, at least 1 g / L, at least 1.2 g / L, at least 1.4 g / L, at least 1.6 g / L, at least 1.8 g / L, at least 2 g / L, at least 2.5 g / L, at least 3 g / L, at least 3.5 g / L, at least 4 g / L, at least 4.5 g / L, at least 5 g / L, at least 5.5 g / L, at least 6 g / L, at least 6.5 g / L, at least 7 g / L, at least 7.5 g / L, at least 8 g / L, at least 8.5 g / L g / L, at least 9 g / L, at least 9.5 g / L, at least 10 g / L, at least 15 g / L, or at least 20 g / L. In some embodiments, the protein titer produced from cells in taurine-supplemented medium is at least 2%, at least 3%, at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23% higher, at least 24% higher, at least 25% higher, at least 26% higher, at least 27% higher, at least 28% higher, or at least 29% higher than the titer of protein (yield) from similar or identical cells grown in medium not supplemented with taurine. In some embodiments, the protein product (protein of interest) is an antibody, a human antibody, a humanized antibody, a chimeric antibody, a monoclonal antibody, a multispecific antibody, a bispecific antibody, an antigen-binding antibody fragment, a single-chain antibody, a dibody, tribody, or tetrabody, a Fab fragment or an F(ab')2 fragment, an IgD antibody, an IgE antibody, an IgM antibody, an IgG antibody, an IgG1 antibody, an IgG2 antibody, an IgG3 antibody, or an IgG4 antibody. In one embodiment, the antibody is an IgG1 antibody. In one embodiment, the antibody is an IgG2 antibody. In one embodiment, the antibody is an IgG4 antibody. In one embodiment, the antibody is a chimeric IgG2 / IgG4 antibody. In one embodiment, the antibody is a chimeric IgG2 / IgG1 antibody. In one embodiment, the antibody is a chimeric IgG2 / IgG1 / IgG4 antibody. In some embodiments, the antibody is selected from the group consisting of an anti-Programmed Cell Death 1 antibody (e.g., an anti-PD1 antibody as described in Pub. of U.S. Patent Application No. US2015 / 0203579A1), an anti-Programmed Cell Death Ligand 1 (e.g., an anti-PD-L1 antibody as described in Pub. of U.S. Pat. No. US2015 / 0203580A1), an anti-DII4 antibody, an anti-Angiopoietin-2 antibody (e.g., an anti-ANG2 antibody as described in Pat. U.S. Patent No. 9,402,898), an anti-Anglopoietin-type 3 antibody (e.g., an anti-AngPtl3 antibody as described in U.S. Patent No. 9,018,356), an anti-platelet-derived growth factor receptor antibody (e.g., an anti-PDGFR antibody as described in U.S. Patent No. 9,265,827), an anti-Erb3 antibody, an anti-Prolactin Receptor antibody (e.g., an anti-PRLR antibody as described in U.S. Patent No. 9,302,015), an anti-Complement 5 antibody (e.g., an anti-C5 antibody as described in U.S. Patent Application Pub. No. US2015 / 0313194A1), an anti-TNF antibody, an anti-epidermal growth factor receptor antibody (e.g., an antibody anti-EGFR as described in U.S. Patent No. 9,132,192 or an anti-EGFRvlll antibody as described in U.S. Patent Application No.US2015 / 0259423A1), an anti-Proprotein Convertase Subtilisin Kexin-9 antibody (e.g., an anti-PCSK9 antibody as described in U.S. Patent No. 8,062,640 or in the Patent Application Publication of the. United States Patent No. US2014 / 0044730A1), an anti-Growth and Differentiation Factor 8 antibody (e.g., an anti-GDF8 antibody, also known as an anti-myostatin antibody, as described in U.S. Patent Nos. 8,871,209 or 9,260,515), an anti-Glucagon Receptor antibody (e.g., an anti-GCGR antibody as described in the Publications of U.S. Patent Applications Nos. US2015 / 0337045A1 or US2016 / 0075778A1), an anti-VEGF antibody, an anti-IL1R antibody, an anti-interleukin 4 receptor antibody (e.g., an anti-IL4R antibody as described in U.S. Patent Application No. US2014 / 0271681A1 or U.S. Patent Nos. 8,735,095 or 8,945,559), an anti-interleukin 6 receptor antibody (e.g., an anti-IL6R antibody as described in U.S. Patent Nos. 7,582,298, 8,043,617, or 9,173,880), an anti-IL1 antibody, an anti-IL2 antibody, an anti-IL3 antibody, an anti-IL4 antibody, an anti-IL5 antibody, an antibody anti-IL6, an anti-IL7 antibody, an anti-interleukin 33 antibody (e.g., an anti-IL33 antibody as described in U.S. Patent Application Publications Nos. US2014 / 0271658A1 or US2014 / 0271642A1), an anti-respiratory syncytial virus antibody (e.g.an anti-RSV antibody as described in U.S. Patent Application Publication No. US2014 / 0271653A1), an anti-Differentiation Cluster 3 antibody (e.g., an anti-CD3 antibody, as described in U.S. Patent Application Publications Nos. US2014 / 0088295A1 and US20150266966A1, and in U.S. Application No. 62 / 222,605), an anti-Differentiation Cluster 20 antibody (e.g., an anti-CD20 antibody as described in U.S. Patent Application Publications Nos. US2014 / 0088295A1 and US20150266966A1, and in U.S. Patent No. 7,879,984), an anti-CD19 antibody, an anti-CD28 antibody, an anti-Differentiation Cluster-48 (e.g., an anti-CD48 antibody as described in U.S. Patent No. 9,228,014), an anti-Fel d1 antibody (e.g., as described in U.S. Patent No. 9,079,948), an anti-Middle East Respiratory Syndrome virus (e.g.an anti-MERS antibody as described in U.S. Patent Application Publication No. US2015 / 0337029A1), an anti-Ebola virus antibody (e.g., as described in U.S. Patent Application Publication No. US2016 / 0215040), an anti-Zika virus antibody, an anti-Lymphocyte Activation Gene 3 antibody (e.g., an anti-LAG3 antibody or an anti-CD223 antibody), and an anti-45 antibody. Activin A. In some embodiments, the bispecific antibody is selected from the group consisting of an anti-CD3 x anti-CD20 bispecific antibody (as described in Publications of U.S. Patent Applications Nos. US2014 / 0088295A1 and US20150266966A1), an anti-CD3 x anti-Mucin 16 bispecific antibody (e.g., an anti-CD3 x anti-Muc16 bispecific antibody), and an anti-CD3 x anti-prostate-specific membrane antigen bispecific antibody (e.g., an anti-CD3 x anti-PSMA bispecific antibody). In some embodiments, the protein of interest is selected from the group consisting of alirocumab, sarilumab, fasinumab, nesvacumab, dupilumab, trevogrumab, evinacumab, and rlnucumab. All publications mentioned throughout this description are incorporated herein by reference in their entirety. In some embodiments, the protein of interest is a recombinant protein containing an Fe residue and another domain (e.g., an Fe fusion protein). In some embodiments, an Fe fusion protein is a receptor Fe fusion protein, which contains one or more extracellular domains of a receptor coupled to an Fe residue. In some embodiments, the Fe residue comprises a hinge region followed by a CH2 and CH3 domain of an IgG. In some embodiments, the Fe receptor fusion protein contains two or more distinct receptor chains that bind to a single ligand or to multiple ligands. For example, an Fe fusion protein is a TRAP protein, such as an IL-1 trap (e.g., rllonacept, which contains the IL-1RAcP ligand-binding region fused to the Fe-fused extracellular 11-1R1 region of hlgG 1; see U.S. Patent No. 6,927).004, which is incorporated herein by reference in its entirety), or a VEGF trap (for example, aflibercept or ziv-aflibercept, which contains the Ig domain 2 of the VEGF receptor Flt1 fused to the Ig domain 3 of the VEGF receptor Flk1. I fused to Fe of hlgG1; see U.S. Patent Nos. 7,087,411 and 7,279,159). In other embodiments, an Fe fusion protein is an ScFv-Fc fusion protein, which contains one or more antigen-binding domains, such as a variable heavy chain fragment and a variable light chain fragment, of an antibody coupled to an Fe moiety. The present invention is not limited to any particular cell type for protein production. Examples of cell types suitable for protein production include mammalian cells, insect cells, avian cells, bacterial cells, and yeast cells. The cells may be stem cells or recombinant cells transformed with a vector for recombinant gene expression, or cells transfected with a virus to produce viral products. The cells may contain a recombinant heterologous polynucleotide construct encoding a protein of interest. That construct may be an episome or an element physically integrated into the cell's genome. The cells may also produce a protein of interest without having that protein encoded in a heterologous polypeptide construct.In other words, the cell may naturally encode the protein of interest, such as a B cell producing an antibody. The cells may also be primary cells, such as chicken embryonic cells, or primary cell lines. Examples of useful cells include BSC cells, LLC-MK cells, CV-1 cells, COS cells, VERO cells, MDBK cells, MDCK cells, CRFK cells, RAF cells, RK cells, TCMK-1 cells, LLCPK cells, PK15 cells, LLC-RK cells, MDOK cells, BHK-21 cells, chicken embryonic cells, NS-1 cells, MRC-5 cells, WI-38 cells, BHK cells, 293 cells, RK cells, Per.C6 cells, and CHO cells. In various embodiments, the cell line is a derivative of CHO cells, such as CHO-K1, CHO DUX B-11, CHO DG-44, Veggie-CHO, GS-CHO, S-CHO, or CHO lee mutant lines. In one embodiment, the cell, which is a CHO cell, ectopically expresses a protein. In one embodiment, the protein comprises an immunoglobulin heavy chain region, such as a CH1, CH2, or CH3 region. In one embodiment, the protein comprises a CH2 and CH3 region of human or rodent immunoglobulin. In one embodiment, the protein comprises a CH1, CH2, and CH3 region of human or rodent immunoglobulin. In one embodiment, the protein comprises a hinge region and a CH1, CH2, and CH3 region. In one embodiment, the protein comprises a variable immunoglobulin heavy chain domain. In one embodiment, the protein comprises a variable immunoglobulin light chain domain. In one embodiment, the protein comprises a variable immunoglobulin heavy chain domain and a variable immunoglobulin light chain domain.In one embodiment, the protein is an antibody, such as a human antibody, a rodent antibody, or a human / rodent chimeric antibody (e.g., human / mouse, human / rat, or human / hamster). A production phase can be carried out at any culture scale, from shaker flasks or wave bags to one-liter bioreactors and large-scale industrial bioreactors. Similarly, an expansion phase of Seed Train cell cultures can be performed at any culture scale, from shaker flasks or wave bags to one-liter bioreactors or larger. A large-scale process can be carried out in volumes from approximately 100 liters up to 20,000 liters or more. One or more different methods, such as temperature change or chemical induction, can be used to control protein production. A growth phase can be conducted at a higher temperature than a production phase.For example, a growth phase can occur at an initial temperature of approximately 35°C to 38°C, and a production phase can occur at a second temperature of approximately 29°C to 37°C, optionally from approximately 30°C to 36°C or from approximately 30°C to 34°C. Additionally, chemical inducers of protein production, such as caffeine, butyrate, tamoxifen, estrogen, tetracycline, doxycycline, and hexamethylene bisacetamide (HMBA), can be added concurrently with, before, or after a temperature change. If inducers are added after a temperature change, they can be added from one hour to five days after the temperature change, or from one to two days after the temperature change. Cell cultures for production can be run as a continuous-feed culture system, such as in a chemostat (see C. Altamirano et al.)., 2001 supra), or according to a fed-batch process (Huang, 2010 supra). The invention is useful for improving protein production through cell culture processes. The cell lines used in the invention can be genetically modified to express a polypeptide of commercial or scientific interest. Genetic modification of the cell line involves transfecting, transforming, or transducing the cells with a recombinant polynucleotide molecule, or otherwise altering them (for example, by homologous recombination and gene activation or fusion of a recombinant cell with a non-recombinant cell) so as to cause the host cell to express a desired recombinant polypeptide. The methods and vectors for genetically manipulating The techniques for cloning cells or cell lines to express a polypeptide of interest are well known to those skilled in the art; for example, various techniques are illustrated in Current Protocols in Molecular Biology, Ausubel et al., eds. (Wiley & Sons, New York, 1988, and quarterly updates); Sambrook et al., Molecular Cloning: A Laboratory Manual (Cold Spring Laboratory Press, 1989); and Kaufman, RJ, Large Scale Mammalian Cell Culture, 1990, pp. 15-69. A wide variety of cell lines suitable for growth in culture are available from the American Type Culture Collection (Manassas, VA) and commercial vendors. Examples of cell lines commonly used in industry include VERO, BHK, HeLa, CVI (including Cos), MDCK, 293, 3T3, myeloma cell lines (e.g., NSO, NSI), PC12, WI38 cells, and Chinese hamster ovary (CHO) cells. CHO cells are widely used for the production of complex recombinant proteins, such as cytokines, clotting factors, and antibodies (Brasel et al. (1996), Blood 88:2004-2012; Kaufman et al. (1988), J. Biol Chem 263:6352-6362; McKinnon et al. (1991), J Mol Endocrinol 6:231-239; Wood et al. (1990), J Immunol. 145:30113016). Dihydrofolate reductase (DHFR)-deficient mutant cell lines (Urlaub et al. (1980), Proc Nati Acad Sci USA 77: 4216-4220), DXBI 1 and DG-44, are desirable CHO host cell lines because the efficient, selectable, and amplifiable DHFR gene expression system allows for high-level recombinant protein expression in these cells (Kaufman RJ. (1990), Meth Enzymol 185:537-566). Additionally, these cells are easy to manipulate as adherent or suspension cultures and exhibit relatively good genetic stability. CHO cells and recombinantly expressed proteins have been extensively characterized and approved for clinical and commercial manufacturing by regulatory agencies.In some embodiments, CHO cell lines are cell lines as described in U.S. Patent Application Publications Nos. 2010 / 0304436 A1, 2009 / 0162901 A1 and. 2009 / 0137416 A1, and US Patents Nos. 7,455,988 B2, 7,435,553 B2, and 7,105,348 B2. The scope of the present invention is not limited by the specific embodiments described herein, which are for illustrative purposes regarding individual aspects or embodiments of the invention. Functionally equivalent methods and components are within the scope of the invention. Several modifications of the invention, in addition to those described herein, are apparent to those skilled in the art from the foregoing description and accompanying drawings. These modifications fall within the scope of the invention. EXAMPLES EXAMPLE 1: Improved Antibody Titers Due to Taurine Supplementation Example 1A - High-Performance Shaker Flask Culture: 250 mL shaker flasks were inoculated from a seed culture of a CHO-K1-derived monoclonal antibody (Ab1) producing cell line. The inoculated cells were cultured at 35.5°C for seventeen days and provided with glucose and other supplemental nutrients as needed. The cells were cultured in chemically defined base medium (hydrolysate-free and serum-free). Each culture flask was either unsupplemented (Flask 1a), or supplemented with 1 mM taurine on day 0 (Flask 1b). TABLE 2: Average Antibody Titers on Day 17 (g / L) and Approximate Titer Increase (%) with Relation to the Reference Point Supplement Bottle Middle Titer of Ab1 1a Unsupplemented* 7.3 g / L 1b Taurine 7.9 g / L *Reference control for % titer increase; Bottle 1b compared to titer in unsupplemented medium (Bottle 1a). The difference in final titer between unsupplemented and supplemented culture is statistically significant (p < 0.05). The protein titration values ​​collected on day 17 were calculated and were statistically significant (p < 0.05) compared to the reference point. Cultures supplemented with taurine exhibited an overall increase of 8% in final protein titer compared to non-supplemented cultures. Example 1B - Benchtop Bioreactors: In a similar example, albeit on a larger production scale, 2L bioreactors were inoculated with a seed culture of a monoclonal antibody-producing cell line (Ab2, Ab3, or Ab4) derived from CHO-K1. The inoculated cultures were grown at 35.5 °C, with an OD setpoint of 40.4% and an air injection rate of 22 cc for 14 days. The Ab2 and Ab3 processes had pH setpoints of 7.0 ± 0.15, while the Ab4 process had a pH setpoint of 7.13 ± 0.27. Glucose feed and antifoam were provided. ·. and basal feeding to the bioreactors as needed. Cultures were grown in unsupplemented medium (Bioreactor 2a, 3a, 4a) or grown in approximately 1 mM taurine-supplemented medium (Ab2 and Ab3) or approximately 3 mM taurine-supplemented medium (Ab4), added on day 0 of production (Bioreactors 2b, 3b and 4b, respectively). The antibody yield (titer) was 6.4 g / L for Ab2-producing cells; however, cells cultured with taurine yielded 8 g / L of protein. The 24% increase in titer compared to cells cultured without taurine supplementation was statistically significant (p < 0.05). The resulting final titers for Ab3-producing and Ab4-producing cultures were also significantly higher (p < 0.05) after 14 days (11% and 20%, respectively) compared to cultures not supplemented with taurine. See Table 3. TABLE 3: Average Antibody Titers on Day 14 (g / L) and Approximate Titer Increase (%) Relative to the Reference Point Supplement Bio- Titer of Ab2 Bio- I Titer of Bio- Titer of Medium reactor# rreactor# Ab3 rreactor# Ab4 6.6 4.4 Unsupplemented* 2a 6.4 g / L 3a g / L 4a g / L 7.3 5.3 Taurine 2b 8 g / LA 24% 3b 11% 4b 20% g / LA g / LA *The unsupplemented medium is the reference control for the % titer increase, where the % titer increase of Bioreactors 2b, 3b, or 4b is compared with the titer in the unsupplemented medium (Bioreactors 2a, 3a, or 4a, respectively). The differences in the final titer between the supplemented and non-supplemented crops are statistically significant (p < 0.05). A time course was plotted with respect to protein titer for the cell culture producing Ab3 and a significant improvement in protein titer was observed due to taurine supplementation each day of culture, starting on day 6. TABLE 4: Improvement of Antibody Titers (g / L) Due to Taurine Supplementation at Representative Time Points Bioreactor Medium Supplement Ab3 Titer on Day 6 Ab3 Titer on Day 9 Ab3 Titer on Day 14 3a Unsupplemented* 1.7 g / L 4.1 g / L 6.6 g / L 3b Taurine 1.9 g / L 12% 5.3 g / L 29% 7.3 g / L 11% 'Approximate increase (%) compared to unsupplemented medium collected on the same day. Increase in titer with taurine supplementation is statistically significant (p < 0.05) compared to unsupplemented culture. A significant improvement in titer was observed in production culture as early as day 6 (12% increase compared to the same culture without taurine supplementation). See also Figure 1. The maximum difference over this time course was observed on day 9 (significant increase (p < 0.05) of 29% in Blorreactor 3b compared to 3a), and a significant titer increase (p < 0.05) of 11% was observed on the final day (14) of culture. The benefits of protein production from taurine supplementation are observed across different scales (Example 1A and 1B) and different cell lines (Example 1B). EXAMPLE 2: Productivity Consistent with Concentrations Taurine Variables in a High-Yield Shake-Flat Culture The consistency of the protein titer was tested by varying the amount of taurine added to the culture on production day 0. 250 mL shaker flasks were inoculated with a seed culture of a monoclonal antibody (Ab1)-producing cell line derived from CHO-K1. The inoculated cells were cultured at 35.5°C for fourteen days, and glucose and other supplemental nutrients were fed as needed. The cells were cultured in a chemically defined base medium (hydrolysate-free and serum-free). Each culture contained either no taurine (unsupplemented) or taurine at concentrations of 0.1 mM, 0.3 mM, 0.5 mM, 0.7 mM, 1 mM, 3 mM, 5 mM, 7.5 mM, or 10 mM. TABLE 5: Average Antibody Titers on Day 14 (g / L) for Cultures Yo Supplemented with 0.1 to 10 mM Taurine Yo Shaker Bottle 5a Medium Supplement Unsupplemented* Ab1 titer 6.5 g / L 5b 0.1 mM Taurine* 6.7 g / L 3% 5c 0.3 mM TaurineA 6.8 g / L 5% 5d 0.5 mM TaurineA 6.9 g / L 6% 5e 0.7mM 7.0g / L 8% TaurineA 5f 1mM 7.0g / L 8% TaurineA 5g 5mM 7.1g / L 9% TaurineA 5h 7.5mM 7.1g / L 9% TaurineA 5i 10mM 7.1g / L 9% TaurineA *The unsupplemented mean is the reference control for % increase in titer. #The difference in the final title is statistically significant compared to the control without supplementation (p < 0.1). The difference in the final titer is statistically significant compared to the unsupplemented control (p < 0.05). Yo It was demonstrated that varying the amount of taurine supplementation consistently resulted in high titers when taurine supplementation was added in a range of at least 0.1 mM to 10 mM. The final titers for the taurine-supplemented conditions were statistically different from the non-supplemented condition. For 0.1 mM taurine, p < 0.1, while p < 0.05 for 0.3 mM to 10 mM taurine. EXAMPLE 3: Trial of the Variation of Taurine Feeding Schedules in a High Shaker Flask Culture Performance EXAMPLE 3A: Addition of Taurine during the Seed Train Phase: The benefits of adding taurine to the culture during the seed train phase were evaluated in the high-throughput shaker flask model. In flask 6a (Table 6), Ab1-producing CHO cells were thawed in chemically defined basal medium (hydrolysate-free and serum-free) supplemented with 1 mM taurine. The basal medium taurine concentration was maintained at 1 mM throughout the expansion phase. During production, the basal culture medium was supplemented with 1 mM of taurine on day 0. Glucose and basal nutrient feeding were supplied as needed during the 17-day production. The cells in flask 6b were grown in a chemically defined basal medium (hydrolysate-free and serum-free) taurine-free (unsupplemented) throughout the entire serial expansion phase (“seed train”). On day 0 of production, the basal culture medium was supplemented with 1 mM taurine. For 17 days of production, glucose and basal nutrient feeds were provided as needed. TABLE 6: Average Antibody Titers on Day 17 for Cultures Supplemented with 1 mM Taurine during Different Phases of the Process 1 mM Addition Flask Taurine Stir Titer Ab1 6a Cell Culture Phases of “Seed 7.7 g / L 6b Train” and Production Only Production Phase 7.8 g / L The differences in final title (day 17) are not statistically significant (p >0.1). The final titer values ​​(day 17) for both conditions (taurine supplementation in production only or combined Seed Train and production cell cultures) are similar. The resulting titers are not statistically significant (p > 0.1). The benefit of adding taurine in the seed train phase is analogous to taurine supplementation in the production phase. EXAMPLE 3B: Variation of Taurine Feeding Schedules During the Production Phase: To determine whether variation of conventional taurine feeding plans had any effect on protein titer for taurine-supplemented cultures, additional experiments were conducted in analog shake-flask cultures growing CHO cells that produce Ab1. The cells were subjected to variable culture conditions similar to Example 2, where the feeding schedule was the same as before, with glucose / basal nutrient feeding added as needed. The cultures producing Ab1 were supplemented with a total of 5 mM taurine. Similar productivity (7.1 g / L, 6.8 g / L, and 7.0 g / L) was observed under the varying taurine feeding schedules. The titration values ​​as compared in this experiment were not statistically different (p > 0.1) (see Table 7). TABLE 7: Average Antibody Titers on Day 14 (g / L) for Cultures Supplemented with 5 mM Taurine with Variable Programs Ab1 Title Programming Taurine Day 14 mM day 0 7.1 g / L

Claims

1. A method for culturing recombinant eukaryotic cells for enhanced recombinant protein production, characterized in that it comprises the steps of: (a) propagating or maintaining the cells in a chemically defined cell culture medium during the growth phase, and (b) supplementing the base cell culture medium with 0.1 mM to 10 mM L-taurine and 0.09 mM to 0.9 mM ornithine and expressing a recombinant protein of interest during the production phase, wherein the addition of L-taurine increases the titer of the recombinant protein of interest by 3% to 29% compared to cells expressing the protein of interest in a cell culture medium containing less than 0.1 mM L-taurine. Sixteen claims follow.