Foam control agent for fermentation processes

Abstract

Methods include controlling foam during a fermentation process, the method including adding to a fermenting broth a foam-controlling amount of one or more polyalkoxylated alcohols having the general formula: R-[AO]n, where R is a linear or branched C1 to C20 alkyl group, AO is an alkylene oxide having three carbons or more, and n represents the average amount of alkylene oxide units that may range from 1 to 50.

Description

[0001] FOAM CONTROL AGENT FOR FERMENTATION PROCESSES

[0002] FIELD

[0003] Embodiments relate to foam control agents and methods for controlling foaming in fermentation processes.

[0004] BACKGROUND

[0005] During the process of ethanol production through the biological fermentation process from sugarcane feedstocks, uncontrolled foaming media can result in a significant loss in production capacity, due to inefficient mixing or pumping, clogged process lines and overflows which result in spills and product waste. Foaming during ethanol production is a major challenge for mills in this sector. Mechanical methods of foam management often have limited effectiveness. The addition of foam control agents is considered to be more practical and is more widely employed to minimize production losses due to foaming. A foam control system can include a defoamer and an antifoamer, which act to treat and prevent excessive foam.

[0006] While foam control systems have addressed a number of fermentation issues, there are developing concerns regarding the production of byproducts from some additives. Particularly, surfactants and emulsifiers produced with ethylene oxide are susceptible to various side reactions that produce 1 ,4-dioxane, a byproduct that is considered a carcinogen in several markets, including those within Asia, the European Union, and a potential hazard in the United States and Latin America. Existing solutions have yet to be found that maintain the same level of foam control, while minimizing the potential for environmental and health concerns.

[0007] Summary

[0008] In an aspect, embodiments disclosed herein are directed to methods of controlling foam during a fermentation process, the method including adding to a fermenting broth a foamcontrolling amount of one or more polyalkoxylated alcohols having the general formula: R-[AO]n, where R is a linear or branched Cl to C20 alkyl group, AO is an alkylene oxide having three carbons or more, and n represents the average amount of alkylene oxide units that may range from 1 to 50.

[0009] Detailed Description

[0010] Embodiments relate to foam control agents and methods for controlling foaming in fermentation processes. Foam control agents may include polyalkoxylated ether and alcohols that may be used as antifoamers to reduce foam formation and / or as defoamers to reduce existing foams. Foam control agents disclosed herein may be substantially free (i.e., 100 ppb or less) from 1 ,4 dioxane, whether present as an impurity or degradation byproduct.

[0011] Foam control agents disclosed herein include polyalkoxylated alcohols prepared by polyaddition of alkylene oxides onto a hydroxy functional starter compound in the presence of catalysts known in the art. Polyalkoxylated alcohols may be prepared from a starter compound and 1 to 50 equivalents of at least one alkylene oxide. Starter compounds may have a hydroxyl functionality of 1 to 8. Tn some cases, starter compounds may include C6 to C20 alcohols, including linear or branched alcohols, such as 2-ethyl hexanol, 2-propyl heptanol, 2,6,8-trimethyl- 4 nonanol, and the like. Other starter compounds may include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,4-butanediol, 1,6- hexanediol, triethanolamine, diethanolamine, diisopropanolamine, bisphenol A, glycerol, diglycerol, triglycerol, trimethylolpropane, di(trimethylolpropane) pentaerythritol, dipentaerythritol, tripentaerythritol, sugars and sugar alcohols such as sucrose and sorbitol, and the like.

[0012] Alkylene oxides used to prepare polyalkoxylated alcohols may include those having a carbon number of C3 or more, such as in a range of C3 to C8. Examples of suitable alkylene oxides include propylene oxide, butylene oxide, pentylene oxide, mixtures of oxides, and the like. In some cases, polyalkoxylated alcohols may have the general formula R-[AO]n, where R is a linear or branched Cl to C20 alkyl group, AO is an alkylene oxide having three carbons or more, and n represents the average amount of alkylene oxide units that may range from 1 to 50. In some cases, R may be at least C8 and n may be 10 or less. The starter compound and / or alkylene oxide may be derived from natural or plant-based materials.

[0013] Polyalkoxylated alcohols may be derived from the alkoxylation of a blend of starter alcohols. In such cases, R in the formula R-|AOJndesignates a mixture of alkyl chains. R may be a mixture of two alkyl chains present at a ratio of first alkyl to second alkyl ranging from 1 :4 to 4:1. For example, polyalkoxylated alcohols include a mixture of C8 and CIO alkyl at a weight ratio ranging from 40:60 to 60:40 (such as 44:56), and C12 and C14 alkyl at a weight ratio ranging from 30:70 to 70:30.

[0014] Polyalkoxylated alcohols disclosed herein may have a weight average molecular weight in a range of 100 Da to 10,000 Da, 150 Da to 8,000 Da, or 200 Da to 5,000 Da. In some cases, polyalkoxylated alcohols may have a propylene oxide content (i.e., an alkylene oxide segment derived from polymerization of propylene oxide) at a percent by weight (wt%) ranging from 20 wt% to 90 wt%, 30 wt% to 80 wt%, or 50 wt% to 75 wt%. Polyalkoxylated alcohols may be used in fermentation processes to control the level of foam in a fermentation liquor, i.e., broth, at or below a desired level during the fermentation process. Foam control agents may be added prior to or at the start of the fermentation process, and / or added intermittently (e.g., on a dosage schedule or as needed). In some cases, polyalkoxylated alcohols may be used in an amount of 1 to 500,000 parts per million (ppm), such as in a range of 1 to 10,000 ppm, or 1 to 300ppm. Foam control agent addition can be continuous or intermittent. For example, a foam control agent may be added at 5 to 250 microliters per liter of fermenting liquor before fermentation process starts, or every 10 to 60 minutes during fermentation process, or each time foam height reaches the process control boundaries. Foam control agents may also be added as a mixture containing one or more additional foam control agents and / or hydrophobic materials.

[0015] Foam control agents may include one or more polyalkoxylated alcohols at a percent by weight (wt%) ranging from 0.01 wt% to 100 wt%. In some cases, foam control agents may include one or more additives, such as mineral and vegetable oils, silicon-based materials, solvents, surfactants, waxes, minerals, stabilizers, antioxidants, fillers and the like.

[0016] Foam control agents may include a dispersing agent that facilitates distribution of the foam control agent through the fermenting broth. Dispersing agents may include solvents such as water, hydrocarbons (both aromatic and aliphatic), and oxygenated solvents (alcohols, ketones, aldehydes, ethers, glycol ethers, esters, and glycol ether esters) and the like.

[0017] Foam control agents may include one or more surfactants or emulsifiers suitable for improving the overall foam control performance of the formulation, the compatibility of the foam control agent on the feedstock or forming an emulsion with the composition of polyalkoxylated alcohol. The optional surfactant or emulsifier may be anionic, cationic or nonioic. Examples of suitable anionic surfactants or emulsifiers are alkali metal, ammonium and amine soaps; the fatty acid part of such soaps contains preferably at least 10 carbon atoms. The soaps can also be formed "in situ;" in other words, a fatty acid can be added to the oil phase and an alkaline material to the aqueous phase.

[0018] Other examples of suitable anionic surfactants or emulsifiers are alkali metal salts of alkylaryl sulfonic acids, sodium dialkyl sulfosuccinate, sulfated or sulfonated oils, e.g., sulfated castor oil; sulfonated tallow, and alkali salts of short chain petroleum sulfonic acids. Suitable cationic surfactants or emulsifiers are salts of long chain primary, secondary or tertiary amines, such as oleylamide acetate, cetylamine acetate, di-dodecylamine lactate, the acetate of aminoethylaminoethyl stearamide, dilauroyl triethylene tetramine diacetate, l-aminoethyl-2-heptadecenyl imidazoline acetate; and quaternary salts, such as cetylpyridinium bromide, hexadecyl ethyl morphohnium chloride, and diethyl di-dodecyl ammonium chloride and the like.

[0019] Examples of suitable nonionic surfactants or emulsifiers are condensation products of higher fatty alcohols with ethylene oxide, such as the reaction product of oleyl alcohol with 10 ethylene oxide units; condensation products of alkylphenols with ethylene oxide, such as the reaction product of isoctylphenol with 12 ethylene oxide units; condensation products of higher fatty acid amides with 5, or more, ethylene oxide units; polyethylene glycol esters of long chain fatty acids, such as tetraethylene glycol monopalmitate, hexaethyleneglycol monolaurate, nonaethyleneglycol monostearate, nonaethyleneglycol dioleate, tridecaethyleneglycol monoarachidate, tricosaethyleneglycol monobehenate, tricos aethyleneglycol dibehenate, polyhydric alcohol partial higher fatty acid esters such as sorbitan tristearate, ethylene oxide condensation products of polyhydric alcohol partial higher fatty acid esters, and their inner anhydrides (mannitol-anhydride, called Mannitan, and sorbitol-anhydride, called Sorbitan), such as glycerol monopalmitate reacted with 10 molecules of ethylene oxide, pentaerythritol monooleate reacted with 12 molecules of ethylene oxide, sorbitan monostearate reacted with 10- 15 molecules of ethylene oxide, mannitan monopalmitate reacted with 10-15 molecules of ethylene oxide; long chain polyglycols in which one hydroxyl group is esterified with a higher fatty acid and other hydroxyl group is etherified with a low molecular alcohol, such as methoxypolyethylene glycol 550 monostearate (550 meaning the average molecular weight of the polyglycol ether) and the like. A combination of two or more of these surfactants may be used; e.g., a cationic may be blended with a nonionic or an anionic with a nonionic.

[0020] The foam control agent may further comprise one or more additives. Examples of additives include ethylene oxide I propylene oxide block copolymers, butylene oxide / propylene oxide block copolymers, ethylene oxide I butylene oxide block copolymers and the like.

[0021] Aqueous fermentation processes are well known in the art. While the foam control agents of the present disclosure are suited for sugarcane bioethanol fermentation processes, these foam control agents are also useful in other fermentation processes including, but not limited to, the production of biofuels from sugar beets, cereal grain, potato, manioc and the like.

[0022] Fermentation methods may include a step of forming an aqueous broth containing yeast and sugar, and a step of contacting a foam control agent with the broth and / or a foam formed on the broth.

[0023] For example, the foam control agent including one or more polyalkoxy lated alcohols may be added by contacting a fermenting broth directly, or by contacting a a foam formed on the fermenting broth. Fermentation methods may also include a step of fermenting the broth to form a biofuel such as ethanol.

[0024] While formulation components and properties have been disclosed individually, it is envisioned that component elements may be included, excluded, or combined in any manner or subcombination utilizing any of the above concentration ranges and nested subranges therein. Further, that the recited formulation properties may be similarly achieved through various combinations of the recited components within the recited ranges.

[0025] Examples

[0026] The following examples are provided to illustrate the embodiments of the invention, but are not intended to limit the scope thereof. Table 1 provides the materials used in the following examples.

[0027] For foam control agents designated “linear C 8 / C 10,” samples were generated from a mixture of C8 and CIO alcohols at a weight ratio of 44:56 (C8:C10) and polyalkylated to the indicated propylene oxide content.

[0028] For foam control agents designated “linear Cl 2 / C 14,” samples were generated from a mixture of C12 and C14 alcohols at a weight ratio of 70:30 (C12:C14) and polyalkylated to the indicated propylene oxide content. Example 1 - Antifoam testing

[0029] In this example, comparative and inventive foam control agents were studied in a bioethanol fermentation process for their ability to prevent foam formation. Fermentest equipment was used for all evaluations. Saccharomyces cerevisiae yeast was obtained in the dry form and hydrated before use. Testing was performed in batches and yeast hydration was repeated for replicated measurements.

[0030] For the antifoam tests, 150 ppm of the sample foam control additive was used and without additional defoamer. Following initiation of fermentation, foam height was monitored and time recorded for foam height at 15, 20 and 25 centimeters. If foam height failed to meet the set heights, the height after 5 minutes was recorded. Table 1 show the results (mean values and standard deviation of triplicates) of time obtained for the foam to reach the height of 15, 20 and 25 cm. Longer time to reach target foam heights is regarded as better performance, where the inability to reach 25 cm (indicated as blank) is the best performance result.

[0031] CE1 is the reference antifoaming agent for foam control during ethanol production from sugarcane. Inventive foam control agents IE1 to IE 17 surveyed the effects carbon chain length and structure (linear and branched) of the alcohol, and the length of the polypropylene oxide segment. The results show that IE1 to IE5 exhibited similar properties to the comparative sample, while IE6 to IE 13 exhibited improved performance. Within samples IE6-IE13 the affect of modifying the length of the PO segment shows that performance changes as the balance between the alcohol and PO segments is varied. IE 14 to IE 17 demonstrated that linear alcohols with carbon chain length of > 8 and PO < 10 improved antifoaming performance over the comparative sample. Example 2 - Defoam testing

[0032] In this example, the ability of comparative and inventive foam control agents to break a formed foam were studied. A series of experiments were performed using 150 ppm of FLUENTCANE™ 178 as standard antifoamer, and 300 ppm of a sample foam control agent (defoamer) were added when the foam reached a height of 20 cm. The residual foam height after the addition of each product, the time to break the foam, and the final foam height after 5 min of experiment were recorded. All defoamers were formulated with 10 wt% of the evaluated product and 90 wt% of a standard commercial mixture of mineral oil, silicone, silica and ethylene bis stearamide (EBS).

[0033] The table below show the results (mean values and standard deviation of triplicates) of foam height after defoamer addition (lower is better) and foam height 5 minutes after defoamer addition (lower is better) in Fermentest. Results of 25cm after 5 minutes mean that foam reached the top of the Fermentest column and air injection needed to be paused (worst case scenario). CE2 is the reference defoamer agent for control of a formed foam during ethanol production from sugarcane. Inventive samples IE1 to IE3 showed that alcohol chain lengths of Carbon < 4 and PO < 10 resulted in similar defoaming effect to the comparative sample, but that effect had limited persistence over times studied. Samples IE6 to IE13 showed that a branched alcohol with carbon chain length of at least 8 carbon number and PO < 10 matches and / or exceeded defoaming performance of the comparative sample. Notably, all inventive samples performed well relative to the comparative foam control agent, with the further advantage that the inventive foam control agents contain no ethylene oxide-derived components capable of producing hazardous 1,4 dioxane byproducts. While the foregoing is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

Claims1. A method of controlling foam during a fermentation process, the method comprising adding to a fermenting broth a foam control agent comprising one or more polyalkoxylated alcohols having the general formula:R-[AO]n where R is a linear or branched C l to C20 alkyl group, AO is an alkylene oxide having three carbons or more, and n represents the average amount of alkylene oxide units that may range from 1 to 50.

2. The method of claim 1, wherein R is at least C8 and n is 10 or less.

3. The method of claim 1, wherein R comprises a mixture of two alkyl chains present at a ratio of a first alkyl to a second alkyl ranging from 1:4 to 4: 1.

4. The method of claim 1, wherein R comprises a mixture of C8 and CIO alkyls at a weight ratio of C8 alkyl to CIO alkyl ranging from 40:60 to 60:40.

5. The method of claim 1, wherein R comprises a mixture of C12 and C14 alkyls at a weight ratio of C12 alkyl to C14 alkyl ranging from 30:70 to 70:30.

6. The method of claim 1, wherein the one or more polyalkoxylated alcohols have a weight average molecular weight ranging from 200 Da to 5,000 Da.

7. The method of claim 1 , wherein the one or more polyalkoxylated alcohols are added to the fermenting broth at a concentration of 1 to 500,000 ppm.

8. The method of claim 1 , wherein the one or more polyalkoxylated alcohols have a propylene oxide content at a percent by weight (wt%) ranging from 50 wt% to 75 wt%.

9. The method of claim 1, wherein the foam control agent is added to the fermentation broth prior to at the start of the fermentation process.

10. The method of claim 1, wherein the foam control agent is added to the fermentation broth intermittently over fermentation.

11. The method of claim 1 , further comprising adding to the fermenting broth at least one other foam control agent or hydrophobic material.

12. The method of claim 1, further comprising adding to the fermenting broth at least one of mineral or vegetable oil, silicon-based material, solvent, surfactant, wax, mineral, stabilizer, antioxidant or filler.

13. The method of claim 1, wherein adding comprises contacting the fermenting broth with the foam control agent.

14. The method of claim 1, wherein adding comprises contacting a foam formed on the fermenting broth with the foam control agent.

15. The method of claim 1, wherein the method comprises producing a bioethanol.

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