Process for the manufacture of acetone, butanol and / or ethanol

Abstract

The invention relates to a process for the manufacture of acetone, butanol and / or ethanol, the process comprising the steps of: i. Providing a plurality of co-products obtained from the yeast propagation processes and / or processes to provide yeast extract; ii. Combining the plurality of co-products from step (i) with a supplementary carbohydrate source and one or more fermentative micro-organisms to create a fermentation culture; and iii. Fermenting the fermentation culture of step (ii) to provide a product comprising butanol, acetone and / or ethanol. The invention further relates to a composition provided by said process, the composition comprising acetone, butanol and / or ethanol.

Description

[0001] Process for the Manufacture of Acetone, Butanol and / or Ethanol

[0002] Field of the Invention

[0003] Yeast extract is considered a natural food product which is rich in peptides, amino acids, vitamins, minerals and yeast derived metabolites. It has a relatively low production cost and can meet a diverse range of food flavour requirements. The production of yeast extract generates co-products which are of low economic value. There is provided alternative processes of using co-products from processes to propagate yeast and to provide yeast extracts.

[0004] Background to the Invention

[0005] Yeast extract can be prepared from brewer’s yeast or baker’s yeast. Brewer’s yeast is mainly obtained by fermenting waste yeast from breweries that produce beer, whilst baker’s yeast typically requires cultivation techniques wherein the yeast is propagated aerobically, under controlled use of substrate.

[0006] Baker’s yeast is principally produced using pure yeast culture and molasses. Yeast cells are typically grown in fermentation vessels operated under aerobic conditions (as under anaerobic conditions the fermentable sugars would be used to form ethanol and carbon dioxide, which would lower yeast levels). During this process, the molasses and any further nutrients are provided incrementally (i.e., in a fed batch process). Once such process is known in the art as the Zulauf method.

[0007] Yeast cells can be recovered from a fermentation vessel by centrifugal yeast separators or via filtration, or the like, as is known in the art. The centrifuged yeast solids can be further concentrated and recovered.

[0008] Yeast extract may be provided by four main processes autolysis, plasmolysis, enzymatic lysis, and physical methods.

[0009] In the production of yeast and yeast extract there are several co-products generated. These can include pre-Condensed Molasses Solubles (pre-CMS) (also known in the art as spent molasses), insoluble and soluble yeast lysis products. The residual co-products derived from the yeast propagation process contain a source of nutrients but are currently considered of low economic value. Typically, they are used as co-products for animal feed, sprayed onto fields (vinasse) or used as part of fertiliser products. It would be advantageous if alternative uses of coproducts could be determined.

[0010] Summary of the invention

[0011] There is a need for sustainable sources of fuels and green chemicals, so as to reduce the use of environmentally damaging fossil fuels. Biofuels provide an alternative source of energy to fossil fuel derived energy sources. Acetone- butanol-ethanol (ABE) fermentation is a well-established process, using bacterial fermentation to produce acetone, butanol and I or ethanol from carbohydrate sources. These solvents can then be used as a variety of sustainable chemicals. Suitably bacteria, typically from the genus Clostridium, are able to utilise various carbohydrates to produce these solvents. Substrates such as pot ale, which comprises dead yeast cells resulting from distillation processes, have been used as substrates for ABE fermentation; however, this substrate is provided following the production of alcohol by the yeast via anaerobic fermentation. Such fermentation is different to the aerobic fermentation of yeast which can be employed to provide baker’s yeast and I or yeast extract. It has been determined that the co-products of processes to propagate yeast and I or provide yeast extract can also be used as suitable substrates in the ABE fermentation process.

[0012] Unlike fermentation processes to produce alcohol, wherein anaerobic fermentation of yeast is undertaken, yeast-production typically uses controlled molasses fed- batch propagation regimes under aerobic conditions (based on the Zulauf process) to optimise biomass production. In such processes yeast cells are kept in a respiratory mode of exponential growth to maximise cell yields (and prevent unwanted ethanol fermentation). Such processes are used for both live yeasts (for baking, brewing, distilling etc) and for production of yeast extracts. The latter processes involves subsequent forced autolysis (heat, salt, enzymes etc) to produce extracts / hydrolysates. Yeast products provided by such processes may include live yeast (cake, dried, cream) and yeast extracts.

[0013] The production of yeast extract / the yeast propagation process generates a number of co-products at different stages of the process.

[0014] Pre-Condensed Molasses Solubles (Pre-CMS) are provided following the propagation of the yeast. These solubles are low in residual sugars. The Pre- Condensed Molasses Solubles co-product obtained in the yeast propagation or yeast extract manufacturing process typically contain a high-water content. To be converted into a material which can be used for animal feed or the like, the Pre- Condensed Molasses Solubles material must be treated to remove the water, condensing the mixture to form Condensed Molasses Solubles. This process is both energy-intensive and economically costly.

[0015] Condensed molasses fermentation solubles (CMS) result when Pre-Condensed Molasses Solubles are treated to remove the residual water content. CMS products are known in the art and generally considered to be the liquid waste with little sugar content formed after fermentation which has been condensed. As will be appreciated, such condensation is typically energy intensive, costly and provides only a marginal economic benefit.

[0016] Once yeast propagation is complete, and yeast cell lysis has occurred, the resulting cell lysis mixture contains both soluble and insoluble fractions. The soluble yeast lysate is used to produce yeast extract and contains amino acids, nucleic acids, salts. The residual insoluble fraction contains insoluble waste products, such as the yeast cell wall. The fractions can be separated using centrifugation. The residual insoluble fraction can be considered Yeast Cell Wall Debris (YCD).

[0017] Finally, any yeast extract material at the end of the yeast extraction process, which does not meet the standard for commercial sale, is termed Yeast Liquor. The substance is a waste co-product of the yeast extraction process, with little economic value.

[0018] There is a need to determine alternative uses for these co-products, which both improves the economic viability and environmental impact of the yeast propagation / yeast extract production process.

[0019] It is known in the art that substrates which comprise dead yeast cells resulting from distillation processes (such as pot ale), can be used as substrates for ABE fermentation; however, the suitability of co-products made from the aerobic yeast production processes (and processes to make yeast extract) has not yet been determined. The inventors have discovered that a combination of co-products derived from the yeast propagation processes and I or processes to provide yeast extract can be used as a substrate for ABE fermentation. Re-using the waste coproducts from the yeast extract manufacturing industry to manufacture ABE both reduces the environmental impact of the yeast extract manufacturing process itself, as well as producing a renewable source of green chemicals.

[0020] According to a first aspect of the invention there is provided a process for the manufacture of acetone, butanol and / or ethanol, the process comprising the steps of: i. Providing a plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract; ii. Combining the plurality of co-products from step (i) with a supplementary carbohydrate source and one or more fermentative micro-organisms to create a fermentation culture; and iii. Fermenting the fermentation culture of step (ii) to provide a product comprising butanol, acetone and I or ethanol.

[0021] Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract may be obtained from yeast cells which have been propagated using an aerobic process, wherein the level of substrates have been controlled. Suitably the plurality of co-products are obtained from yeast cells propagated using the Zulauf technique.

[0022] Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract include Pre-condensed Molasses Solubles (Pre-CMS). Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract include Yeast Cell Debris (YCD). Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract include Condensed Molasses Solubles (CMS). Suitably, the plurality of coproducts obtained from the yeast propagation processes and I or processes to provide yeast extract include Yeast Liquor.

[0023] Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract include Pre-condensed Molasses Solubles (Pre-CMS) and Yeast Cell Debris (YCD). Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract include Pre-condensed Molasses Solubles (Pre-CMS) and Condensed Molasses Solubles (CMS). Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract include Pre-condensed Molasses Solubles (Pre-CMS) and Yeast Liquor. Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract include Condensed Molasses Solubles (Pre-CMS) and Yeast Cell Debris (YCD). Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract include Condensed Molasses Solubles (Pre-CMS) and Yeast Liquor. Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract include Yeast Cell Debris (YCD) and Yeast Liquor.

[0024] Suitably, the plurality of co-products obtained from the yeast propagation processes and / or processes to provide yeast extract include Pre-condensed Molasses Solubles (Pre-CMS) and Yeast Cell Debris (YCD). Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract may further include Condensed Molasses Solubles. Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract may further include Yeast Liquor. Suitably, the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract may further include any other soluble yeast lysate and / or any other insoluble yeast lysate.

[0025] Suitably, a supplementary carbohydrate source is combined with the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably, the supplementary carbohydrate source can be selected from any suitable carbohydrate, for example municipal organic waste, industrial organic waste, agricultural crops and crop residues, wood and forestry waste, marine biomass and bio-energy crops. Suitably, the carbohydrate source may be, for example, potato starch, wheat straw, rice straw, barley straw and com cob. Suitably the supplementary carbohydrate source may be a sugar source. Suitably, the supplementary carbohydrate source may be a monosaccharide or disaccharide. Suitably the supplementary carbohydrate source may be molasses, sucrose, glucose, fructose or xylose. Suitably, the carbohydrate source may be a mixture of the above carbohydrate sources.

[0026] The inventors have determined that Pre-CMS and Yeast Cell Debris co-products obtained from the yeast propagation processes and I or processes to provide yeast extract do not support high solvent yields of ABE fermentation on their own; however, surprisingly, the inventors discovered that (when supplemented with a carbohydrate source) a substrate comprising a combination of both co-products was able to support high yields of ABE fermentation. The inventors have determined that the combination of Pre-CMS and Yeast Cell Debris, when combined with a supplementary carbohydrate substrate, allows for substantially higher production of ABE than when either co-product is provided individually. Advantageously, as these co-products can be taken from the yeast extract production process and used together as a substrate for ABE fermentation, more of the waste products from the yeast extract manufacturing process can be removed from a production facility and re-used in an environmentally beneficial manner. Advantageously, the co-products can be used as a substrate for ABE fermentation in the ratio in which they are produced during the yeast propagation / yeast extract production process. The inventors have, therefore, determined a holistic solution for a known industrial problem, taking the waste coproducts from these processes and utilising them as a substrate for ABE fermentation.

[0027] Suitably, in fermentation cultures comprising Pre-CMS and Yeast Cell Debris any suitable supplementary carbohydrate source may be used. Suitably the carbohydrate source may be, for example, potato starch, wheat straw, rice straw, barley straw and com cob. Suitably, the supplementary carbohydrate source may be a sugar, suitably molasses, sucrose, glucose, fructose or xylose. Suitably, the carbohydrate source may be a mixture of the above carbohydrate sources. Suitably, the supplementary carbohydrate source may be pre-treated before it is added to any fermentation culture or mixture in the process. Suitably, the supplementary carbohydrate source may be pre-treated using enzymes so as to assist their digestion during the process.

[0028] Suitably, the fermentation culture of step (ii) of the process of the present invention may comprise between 15%v / v and 90%v / v of the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 20%v / v and 85%v / v of the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 22%v / v and 85%v / v of the plurality of coproducts obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 25%v / v and 85%v / v of the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 25%v / v and 80%v / v of the plurality of co-products obtained from the yeast propagation processes and / or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 27%v / v and 80%v / v of the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 30%v / v and 80%v / v of the plurality of co-products obtained from yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 35%v / v and 80%v / v of the plurality of co-products obtained from yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 35%v / v and 75%v / v of the plurality of co-products obtained from yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 37%v / v and 75%v / v of the plurality of coproducts obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 40%v / v and 75%v / v of the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 42%v / v and 75%v / v of the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 45%v / v and 75%v / v of the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 47%v / v and 75%v / v of the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 50%v / v and 75%v / v of the plurality of coproducts obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 52%v / v and 75%v / v of the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 55%v / v and 75%v / v of the plurality of co-products obtained from yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 57%v / v and 75%v / v of the plurality of co-products obtained from yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 60%v / v and 75%v / v of the plurality of co-products obtained from yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 60%v / v and 72%v / v of the plurality of co-products obtained from yeast propagation processes and I or processes to provide yeast extract. Suitably the fermentation culture of step (ii) may comprise between 60%v / v and 70%v / v of the plurality of co-products obtained from yeast propagation processes and I or processes to provide yeast extract.

[0029] Suitably, the fermentation culture of step (ii) may comprise between 10%v / v and 85%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 12%v / v and 85%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 14%v / v and 85%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 15%v / v and 85%v / v Pre- Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 17%v / v and 85%v / v. Suitably, the fermentation culture of step (ii) may comprise between 20%v / v and 85%v / v. Suitably, the fermentation culture of step (ii) may comprise between 22%v / v and 85%v / v. Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 25%v / v and 85%v / v. Suitably, the fermentation culture of step (ii) may comprise between 25%v / v and 80%v / v. Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 25%v / v and 78%v / v Pre- Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 25%v / v and 76%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 25%v / v and 75%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 25%v / v and 73%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 25%v / v and 70%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 25%v / v and 67%v / v Pre- Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 25%v / v and 65%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 27%v / v and 65%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 30%v / v and 65%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 32%v / v and 65%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 35%v / v and 65%v / v Pre- Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 35%v / v and 62%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 35%v / v and 60%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 40%v / v and 60%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 42%v / v and 60%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 45%v / v and 60%v / v Pre- Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 40%v / v and 50%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 45%v / v and 50%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 50%v / v and 55%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 50%v / v and 60%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 45%v / v and 60%v / v Pre- Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise between 50%v / v and 65%v / v Pre-Condensed Molasses Solubles. Suitably, the fermentation culture of step (ii) may comprise about 50%v / v Pre- Condensed Molasses Solubles.

[0030] Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 7%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 10%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 12%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 15%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 17%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 20%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 22%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 25%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 27%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 30%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 32%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 35%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 37%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 40%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 45%v / v and 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise about 50%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 45%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 40%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 35%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 30%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 25%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 20%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 17%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 15%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 12%v / v Yeast Cell Wall Debris. Suitably, the fermentation culture of step (ii) may comprise between 5%v / v and 10%v / v Yeast Cell Wall Debris.

[0031] The process of the first aspect comprises providing a supplementary carbohydrate source at step (ii), wherein this carbohydrate source may suitably be one or more sugar sources. Suitably the one or more sugar sources may be any appropriate sugar sources for fermentation. Suitably, the one or more sugar sources may be selected from molasses, glucose or sucrose. Advantageously, the combination of one or more co-products obtained from yeast propagation processes and I or processes to provide yeast extract and a carbohydrate source, for example sugar, is selected to provide an improved yield of solvents produced during the fermentation of the culture (step (iii)).

[0032] Suitably, the fermentation composition at step (ii) may comprise less than 25%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 25%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 24%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 23%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 22%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 21%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 20%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 19%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 18%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 17%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 16%w / v of one or more supplementary carbohydrate sources, w / v. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 15%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 14%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 13%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 12%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 11%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 10%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 9 %w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 8%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 7%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 6%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 0.5%w / v and 5%w / v of one or more supplementary sugar sources. Suitably the fermentation composition at step (ii) may comprise between 1 %w / v and 5%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 1.5%w / v and 5%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 2%w / v and 5%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 2.5%w / v and 5%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise between 3%w / v and 5%w / v of one or more supplementary carbohydrate sources. Suitably the fermentation composition at step (ii) may comprise about 5%w / v of one or more supplementary carbohydrate sources.

[0033] Suitably, the process may further comprise a pre-treatment step between steps (i) and (ii). Suitably, the pre-treatment step may comprise heat-treating the one or more co-products to remove any microbial contamination.

[0034] Suitably, the process may further comprise adding of one or more enzymes into the mixture of co-products, prior to making the fermentation culture of step (ii). Suitably, the one or more enzymes may be any enzyme capable of degrading the yeast cell wall. Suitably, the one or more enzymes may be selected from glycosylhydrolases, oxidoreductases, lyases, and esterases. Suitably, the one or more enzymes may be capable of hydrolysing the yeast cell wall. Suitably, the one or more enzymes may be capable of hydrolysing one or more of the residues selected from: N-acetylglucosamine, mannoproteins, chitin, mannose and glucose residues.

[0035] Suitably, the process may further comprise adding one or more nutrient additives to the fermentative mixture of step (ii). Suitably, the one or more nutrient additives may be selected from nitrogen, phosphates, sulphates, carbonates and sulphates.

[0036] Suitably, the one or more fermentative micro-organisms may be any suitable micro-organism for ABE fermentation. Suitably, the one or more fermentative micro-organisms may be strains of bacteria from the Class Clostridia. Suitably, the one or more fermentative micro-organisms may be strains of solventogenic Clostridia. Suitably, the one or more micro-organisms may be selected from any suitable strain from the species Clostridium acetobutylicum, Clostridium beijerinckii, Clostridium saccharobutylicum, and Clostridium saccharoperbutylacetonicum. Suitably, the one or more fermentative microorganisms may be selected from the strains C. acetobutylicum ATCC 824, C. beijerinckii NCI MB 8052, C. saccharobutylicum P262, C. saccharobutylicum NCP258, C. saccharoperbutylacetonicum N 1-504, C. beijerinckii NCP260 and C. saccharoperbutylacetonicum N1 -4. Suitably, the process may further comprise fermenting the culture at step (iii) for between 24 and 96 hours. Suitably, the process may further comprise fermenting the culture at step (iii) for between 48 and 96 hours. Suitably, the process may further comprise fermenting the culture at step (iii) for between 72 and 96 hours.

[0037] Suitably, the process may further comprise fermenting the culture at step (iii) in an anaerobic environment.

[0038] According to a second aspect of the invention there is provided a composition provided by a process of the first aspect of the invention, the composition comprising acetone, butanol and I or ethanol.

[0039] Suitably, the composition of the second aspect may comprise one or more of acetone, butanol and I or ethanol.

[0040] Elements of the second aspect of the invention may be combined with elements of the first aspect of the invention.

[0041] According to a third aspect there is provided the use of a plurality of co-products derived from the yeast propagation processes and I or processes to provide yeast extract in ABE fermentation. In certain embodiments, the plurality of co-products are selected from Pre-Condensed Molasses Solubles, Condensed Molasses Solubles, Yeast Cell Debris and Yeast Liquor.

[0042] Elements of the third aspect of the invention may be combined with elements of the first or second aspects of the invention.

[0043] Detailed Description of the Invention

[0044] Certain embodiments of the present invention utilise one or more co-products from the yeast extract manufacturing process to carry about ABE fermentation. Surprisingly, the inventors found that co-products from the yeast extract production process, can be used as substrates in an ABE process. This is considered to provide an economic and environmentally advantageous use of the co-products.

[0045] The term “biofuel” refers to any fuel derived from a biomass.

[0046] The term “green chemicals” refers to chemicals that are designed, produced, and utilized in ways that minimize their impact on the environment and human health.

[0047] The term “autolysis” refers to the destruction of a cell through the action of its own enzymes. Lysis refers to destruction of the cell by any means.

[0048] The term “yeast lysate” refers to the total material obtained after lysis of the yeast cells. Yeast lysate contains soluble portions (amino acids, nucleic acids, salts) and insoluble components, such as the Yeast Cell Wall Debris. Yeast autolysate can comprise an insoluble fraction comprising the yeast cell wall debris and a soluble fraction.

[0049] The term “Pre-Condensed Molasses Solubles” (Pre-CMS) refers to the soluble liquid residue obtained after yeast has been propagated using an aerobic process, for example the Zulauf process. It comprises a number of sugars including sucrose, glucose and fructose, as well as comprising proteins, amino acids, organic acids, vitamins and minerals.

[0050] The term “Condensed Molasses Solubles” (CMS) refers to the substance obtained after Pre-Condensed Molasses has been treated to remove the residual water content.

[0051] The present invention will now be described with reference to the following examples which are provided for the purpose of illustration and are not intended to be construed as limiting on the present invention. Brief Description of the Figures

[0052] Figure 1 - A visual analysis of colour, texture, consistency of the co-products produced during the yeast extract manufacturing process.

[0053] Figure 2 - An analysis of solvent yield obtained from fermentation mixtures with Pre-Condensed Molasses Solubles (Pre-CMS) and Yeast Cell Debris (YCD). The graph shows that Pre-CMS and YCD cannot support bacterial growth and solventogenesis in isolation. The graph further demonstrates that when YCD and pre-CMS are combined, an additional supplementary sugar source is required to promote growth and solvent production. The addition of glucose as the supplementary sugar source promoted solventogenesis to levels similar to those seen in the control fermentation culture.

[0054] Figure 3 - ABE solvent yields produced in fermentation cultures with varying concentrations of Pre-CMS and Yeast Cell Debris. Figure 3A shows ABE solvent yields obtained from fermentation cultures containing a range of Pre-CMS concentrations. Figure 3B shows ABE solvent yields obtained from fermentation cultures containing a range of Yeast Cell Debris concentrations.

[0055] Figure 4 - An analysis of solvent yield obtained from fermentation cultures comprising Pre-CMS, Yeast Cell Wall Debris and different supplementary sugar sources. Fig. 4A demonstrates the fermentation cultures (control and yeast coproduct) which have been supplemented with molasses. Fig. 4B demonstrates the fermentation cultures (control and yeast co-product) which have been supplemented with sucrose.

[0056] Figure 5 - Analysis of Clostridium Strains using fermentation cultures comprising Pre-CMS and Yeast Cell Wall Debris. The analysis of strains of Clostridium (detailed in Example 5) demonstrated that all strains produced either greater or equivalent levels of solvent in fermentation cultures comprising 50%v / v Pre-CMS and 20%v / v YCD compared to cultures using TYA (Tryptone Yeast Agar) media. Examples

[0057] Example 1 - An analysis of colour, texture, consistency of the co-products produced during the yeast extract manufacturing process.

[0058] A visual analysis was performed of the co-products obtained from the yeast extract manufacturing process. A representation of the products is demonstrated in Figure 1 . Sample A consists of Pre-Condensed Molasses Solubles (Pre-CMS). Sample B consists of Condensed Molasses Solubles (CMS). Sample C consists of Yeast Liquor (YL). Sample D consists of Yeast Cell Wall Debris (YCD).

[0059] Example 2 - Analysis of solvent yield obtained from a range of fermentation cultures.

[0060] To assess the effect different co-products from the yeast propagation process would have on the ABE solvent yield, a number of fermentation cultures were tested.

[0061] Pre-condensed molasses solubles (pre-CMS) and yeast cell debris (YCD) were obtained. The stocks were stored at -20°C and defrosted at ambient temperature overnight prior to media preparation.

[0062] Fermentation cultures were prepared according to the table below. Each culture was made in triplicate. The Control: ‘TYA + Glucose’ condition is the control condition, containing no yeast co-products, but instead laboratory-grade TYA medium.

[0063] Recipe A - (Pre-CMS-100%) fermentation was carried out in a solution containing 100% pre-CMS and no other substrate.

[0064] Recipe B - The ‘YCD-100%’ fermentation was carried out in a solution containing 100% yeast cell debris and no other substrate.

[0065] Recipe C - The ‘1 :1 PCMS:YCD - fermentation media was made up of 50:50 ratio (v / v) of undiluted PCMS and Yeast Cell Debris, without any additional sugar source.

[0066] Recipe D - The ‘1 :1 PCMS:YCD 40%:40%’ fermentation media was comprised of 40%v / v PCMS, 40%v / v Yeast Cell Debris and 5%w / v glucose solution.

[0067] Recipe E - ‘1 :1 PCMS:YCD 30%:30%’ fermentation media was comprised of 30%v / v PCMS, 30%v / v Yeast Cell Debris and 5%w / v glucose solution.

[0068] Prior to addition of the glucose or inoculum, the mixtures were autoclaved at 121 °C for 15 minutes and incubated in anaerobic conditions overnight. Once the glucose solution was added, the pH of the culture media was adjusted to between pH6.1 and pH6.2. The mixtures were then inoculated with Clostridium saccharoperbutylacetonicum NCI MB 12606.

[0069] The cultures were left to ferment in an anaerobic environment for 72 hours with agitation.

[0070] At the end of fermentation, the final pH of the fermented media was checked (Jenway 3520 pH meter) and 2ml homogenous samples were collected in 2ml- sized microcentrifuge tubes and centrifuged at 13000 rpm for 10 minutes (Heraeus Megafuge 8R). The supernatant was collected and then filtered through 0.2 pm nylon syringe filter. Filtered samples were analysed for solvents on GC, residual sugars and acids concentrations by HPLC.

[0071] Solvent (ethanol, acetone and butanol) analysis was conducted with Hewlett Packard 5890 Series II Gas chromatograph with flame ionisation detector using J&W DB-WAX Ultra Inert Intuvo GC column module, 30 m, 0.25 mm, 0.25 pm (Agilent). Concentrations were determined by reference to ethanol, acetone and butanol (Sigma) standards.

[0072] Acids (acetic and butyric) and glucose analyses were conducted with Waters 2695 separations module HPLC with refractive index detector (RID-20A Shimadzu), equipped with Rezex ROA Organic acid H+ 8% 300 x 7.8 mm column (Phenomenex) with 0.005N sulphuric acid as mobile phase. Components were separated at 50°C. Concentrations were determined by reference to acetic acid, butyric acid (Sigma) and glucose standard.

[0073] Figure 2 discloses solvent yields obtained in each fermentation culture. Cultures containing purely pre-CMS and yeast cell debris failed to produce a solvent yield of above 2g / L (Recipes A and B). These results indicated that it is not possible to obtain economically viable yields of ABE fermentation in a culture medium comprising either Yeast Cell Debris and Pre-CMS alone.

[0074] Additionally, a culture medium containing a 50:50 ratio of Pre-CMS to Yeast Cell Debris, with no additional sugar source, (Recipe C) failed to yield significant solvent production.

[0075] Surprisingly, however, the inventors discovered that using a media comprising a combination of Pre-CMS and Yeast Cell Debris, when the media is additionally supplemented with an additional sugar source (in this case 5% w / v glucose), yielded substantially higher concentrations of solvent (greater than 10g / L) (Recipes D and E). The inventors have also discovered that increasing the glucose concentration in the solution does not improve solvent yield. The total solvent yield in the obtained from the ‘1 :1 PCMS:YCD 40%:40%’ fermentation culture was comparable to the ‘1 :1 PCMS:YCD 30%:30%’ culture. Therefore, the inventors determined that only a small volume of supplementary sugar source is required to enable the bacteria in a PCMS:YCD fermentation cultures to produce ABE.

[0076] The inventors discovered that the combination of Yeast Cell Debris and Pre-CMS was vital for production of solvent yields. Adding a supplementary sugar source to a fermentation culture with exclusively pre-CMS or Yeast Cell Debris did not result in the same solvent yield as when a combination of the yeast co-products was used.

[0077] Example 3 - Analysis of solvent yield obtained from fermentation cultures comprising a range of Pre-CMS and Yeast Cell Debris.

[0078] Having established that a fermentation culture comprising a combination of Yeast Cell Debris and Pre-CMS (with a supplementary sugar source) resulted in substantially higher solvent yields than either component alone, a range of concentrations of each co-product was tested.

[0079] Fermentation cultures were set up as detailed in the below table. A range of Pre- CMS concentrations were tested against a constant concentration of Yeast Cell Debris and vice versa. Glucose was used as a supplementary sugar source.

[0080] The ABE solvent yields produced in each fermentation culture is shown in Figures 3A and 3B below. Figure 3A shows the range of Pre-CMS which is varied, whilst the concentration of Yeast Cell Debris was maintained as constant. All ranges in Pre-CMS produced a solvent yield of between 5g / L and 10g / L. Increasing the concentration of Pre-CMS in the fermentation culture did not result in an increase in solvent yield. The inventors determined that a reasonable solvent yield could be obtained from a range of Pre-CMS concentrations.

[0081] Contrary to the above results, altering the concentration of Yeast Cell Debris did result in an improvement to the solvent yield produced. As the concentration of Yeast Cell Debris in fermentation cultures increased, solvent yield also improved (as seen in Figure 3B). The inventors determined that increasing the concentration of Yeast Cell Debris from 10%v / v to 30%v / v in the fermentation cultures roughly doubled the solvent yield. The results indicate that Yeast Cell Debris contains extra nutrients which improve bacterial growth and solvent production. Surprisingly, the inventors determined that such solvent production is not seen in the absence of pre-CMS (and in conjunction with the supplementary sugar source). The inventors have determined that the combination of pre-CMS and Yeast Cell Debris, when supplemented with an additional sugar source, provides a suitable fermentation culture to facilitate ABE fermentation. The inventors have demonstrated that ABE fermentation can be achieved over a range of concentrations of both Yest Cell Debris and Pre-CMS.

[0082] Advantageously, the inventors have shown that a range of different concentrations of each co-product can be used in ABE fermentation. These ranges encompass those in which Pre-CMS and Yeast Cell Debris are produced during the industrial process to propagate yeast and / or produce yeast extract. The inventors have, therefore, determined a holistic solution for a known industrial problem, taking the waste co-products from these processes and utilising them as a substrate for ABE fermentation.

[0083] Example 4 - Analysis of solvent yield obtained from fermentation cultures comprising Pre-CMS, Yeast Cell Wall Debris and different supplementary sugar sources.

[0084] The effect of different supplementary sugar sources on fermentation cultures comprising yeast propagation co-products was assessed. The use of molasses and sucrose was tested to assess the effect different supplementary sugar sources may have on solvent yield. Fermentation cultures were made as detailed below. In one experiment, the supplementary sugar source tested was molasses (Figure 4A). In a separate experiment, the sugar source tested was sucrose (Figure 4B).

[0085] Fermentations were performed in triplicate. Fermentations were left for 96 hours. The strain C. saccharoperbutylacetonicum N1-4 was used.

[0086] Results of solvent yield for the recipes is shown in the below table and in Figure 4. The recipe comprising 50%v / v Pre-CMS and 20%v / v YCD) showed equivalent or improved solvent yields compared to control sample (TYA), when both molasses and sucrose were used. It is shown that fermentation cultures containing yeast co-products can support ABE fermentation in the presence of a variety of supplementary sugar sources.

[0087] Example 5 - Analysis of Clostridium Strains using fermentation cultures comprising Pre-CMS and Yeast Cell Wall Debris.

[0088] A set of fermentations were carried out using either a fermentation comprising 50%v / v Pre-CMS and 20%v / v YCD or TYA medium. Both cultures contained supplementary sugar source molasses at a final concentration of ~50g / L Three strains of Clostridium were tested to see if there was an effect on strain function in fermentations comprising yeast extract co-products.

[0089] The following strains were compared: i. C. saccharoperbutylacetonicum N1-4; ii. C. saccharobutylicum NCP262; and iii. C. beijerinckii NCIMB 8052.

[0090] Fermentations were performed in triplicate and left for 96 hours.

[0091] Results demonstrated that the three strains tested produced the same or more solvent in the fermentations comprising Pre-CMS and YCD compared with those in standard TYA media (Figure 5).

[0092] As disclosed in the above specification and examples, the inventors have discovered a solution to the industry problem of waste production in the yeast extract manufacturing process. Surprisingly, the inventors discovered that using a combination of co-products from this process provided a suitable substrate for ABE fermentation, meaning that waste products from the yeast propagation / yeast extract industries can be re-used to manufacture green chemicals.

Claims

Claims1. A process for the manufacture of acetone, butanol and I or ethanol, the process comprising the steps of:

1. Providing a plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract; ii. Combining the plurality of co-products from step (i) with a supplementary carbohydrate source and one or more fermentative micro-organisms to create a fermentation culture; and iii. Fermenting the fermentation culture of step (ii) to provide a product comprising butanol, acetone and I or ethanol.

2. The process of claim 1, wherein the one or more co-products is obtained from yeast propagated in an aerobic environment.

3. The process of any preceding claim, wherein the plurality of co-products comprises one or more of Pre-Condensed Molasses Solubles and Yeast Cell Debris.

4. The process of any preceding claim, wherein the plurality of co-products comprises Pre-Condensed Molasses Solubles and Yeast Cell Debris.

5. The process of claims 3 to 4, wherein the plurality co-products further comprises one or more of Condensed Molasses Solubles, and Yeast Liquor.

6. The process of any preceding claim, wherein the fermentation culture of step (ii) comprises between 15%v / v and 90%v / v of the plurality of co-products obtained from the yeast propagation processes and I or processes to provide yeast extract.

7. The process of any preceding claim, wherein the fermentation culture of step (ii) comprises between 10%v / v and 85%v / v Pre-Condensed Molasses Solubles.

8. The process of any preceding claim, wherein the fermentation culture of step (ii) comprises between 5%v / v and 50%v / v Yeast Cell Wall Debris.

9. The process of any preceding claim, wherein the fermentation culture of step (ii) comprises Pre-Condensed Molasses Solubles and Yeast Cell Debris at a ratio between 1 :1 and 7:1 (Pre-Condensed Molasses Solubles:Yeast Cell Debris).

10. The process of any of claims 1 to 8, wherein the fermentation culture of step (ii) comprises Pre-Condensed Molasses Solubles and Yeast Cell Debris at a ratio between 5:1 and 5:4 (Pre-Condensed Molasses Solubles:Yeast Cell Debris).

11. The process of any preceding claim, wherein the fermentation composition at step (ii) may comprise between 0.5%w / v and 25%w / v of one or more supplementary carbohydrate sources.

12. The process of any preceding claim, wherein the supplementary carbohydrate source is a sugar source.

13. The process of claim 12, wherein the one or more sugars is selected from molasses, sucrose, glucose, fructose or xylose.

14. The process of claim 13, wherein the one or more sugars is selected from glucose, sucrose and molasses.

15. The process of any preceding claim, wherein the process further comprises a pre-treatment step between steps (i) and (ii), wherein the pre-treatment step comprises heating the one or more co-products.

16. The process of any preceding claim, wherein the process further comprises a pre-treatment step between steps (i) and (ii), wherein the pre-treatment step comprises providing one or more enzymes to the plurality of co-products.

17. The process of any preceding claim, wherein the one or more fermentative micro-organisms is selected from any suitable strain from the species Clostridium acetobutylicum, Clostridium beijerinckii, Clostridium saccharobutylicum, and Clostridium saccharoperbutylacetonicum.

18. A composition provided by the process of any preceding claim, the composition comprising acetone, butanol and / or ethanol.5

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