BATCH FEED PROCESS FOR FERMENTING SUGARS

Abstract

A batch fermentation process ferments a starch hydrolysate containing 80-98 weight percent of glucose based on total carbohydrate and 0.3-5% weight percent of isomaltose based on total carbohydrate to a fermentation product. A fermentation broth is formed containing a first portion of a total amount of the starch hydrolysate so that the fermentation broth has an initial glucose concentration of at least about 50 g/L. Fermentaion is carried out until the fermentation broth contains 30 g/L or less of glucose. An effective amount of at least one active enzyme that converts isomaltose into glucose is adding to the fermentation broth. Then the remaining portion of the total amount of starch hydrolysate is fed into the fermentation broth to maintain a glucose concentration of from about 5 to about 15 g/L in the fermentation broth throughout the feeding step. The final fermentation broth containing the fermentation product is then produced.

Claims

1-42. (canceled)

43. A fed batch fermentation process for fermenting a starch hydrolysate containing at least 80 weight percent of glucose based on total carbohydrate and 0.3-5% weight percent of isomaltose based on total carbohydrate to a fermentation product, comprising: a) forming a fermentation broth containing a first portion of a total amount of the starch hydrolysate so that the fermentation broth has an initial glucose concentration of at least about 50 g/L; b) fermenting the starch hydrolysate in the fermentation broth in an initial fermentation step to produce a fermentation product until the fermentation broth contains 30 g/L or less of glucose; c) adding to the fermentation broth an effective amount of at least one active enzyme that converts isomaltose into glucose; d) feeding the remaining portion of the total amount of starch hydrolysate containing at least 80 weight percent of glucose based on total carbohydrate and 0.3-5% weight percent of isomaltose based on total carbohydrate into the fermentation broth to maintain a glucose concentration of from about 5 to about 15 g/L in the fermentation broth throughout the feeding step; and e) producing a final fermentation broth containing the fermentation product, wherein during step (d) the glucose concentration is monitored by a real-time monitoring system that indirectly correlates the glucose concentration present in the fermentation broth to a measurement of the carbon dioxide evolution rate and the amount of carbon dioxide present in an off-gas stream from a fermentation vessel containing the fermentation broth, and wherein the real-time monitoring system interfaces with equipment that controls the introduction of starch hydrolysate in step (d).

44. The fermentation process of claim 43, wherein during step d), the carbon dioxide is measured through use of a mass spectrometer or other suitable instrumental technique for measuring the components of the off-gas streams from the fermentation vessel.

45. The fermentation process of claim 43, wherein the real-time monitoring system interfaces with equipment that controls the introduction of starch hydrolysate in step (d).

46. The fermentation process of claim 43, wherein the starch hydrolysate utilized comprises at least 90 percent by weight glucose based on total carbohydrate.

47. The fermentation process of claim 43, wherein the starch hydrolysate utilized comprises at least 95 percent by weight glucose based on total carbohydrate.

48. The fermentation process of claim 43, wherein the starch hydrolysate added in step d) is provided as an addition composition having a solids content of from about 25 to about 70 weight percent.

49. The fermentation process of claim 43, wherein the starch hydrolysate added in step d) is provided as an addition composition having a solids content of from about 30 to about 40 weight percent.

50. The fermentation process of claim 43, wherein the first portion of the total amount of the starch hydrolysate contains from about 50 to about 80 percent of the total amount of starch hydrolysate to be added to the fermentation broth.

51. The fermentation process of claim 43, wherein the final fermentation broth comprises no more than about 1 g/L of isomaltose.

52. The fermentation process of claim 43, wherein the final fermentation broth comprises no more than about 1 g/L of glucose.

53. The fermentation process of claim 43, wherein the final fermentation broth comprises no more than about 0.5 g/L of glucose.

54. The fermentation process of claim 43, wherein the active enzyme is active for the conversion of both isomaltose and maltose into glucose.

55. The fermentation process of claim 43, wherein the fermentation is carried out using yeast.

56. The fermentation process of claim 43, wherein the fermentation product is selected from the group consisting of: amino acids, organic acids, alcohols, polyols, fatty acids, monacyl glycerides, diacyl glycerides, triacyl glycerides, and mixtures thereof.

57. The fermentation process of claim 43, wherein the fermentation product is selected from the group consisting of amino acids and organic acids.

58. The fermentation process of claim 43, wherein the fermentation product comprises an organic acid.

59. The fermentation process of claim 43, wherein the fermentation product comprises lactic acid or 3-hydroxy-propionic acid.

60. The fermentation process of claim 43, wherein the starch hydrolysate contains 90-97% weight percent of glucose based on total carbohydrate.

Description

EXAMPLES

[0043] Representative embodiments of the present invention will now be described with reference to the following examples that illustrate the principles and practice of the present invention.

[0044] The transglucosidase used is based on the TG-L2000 product available from DuPont Biosciences, with the following differences: 1) the final glycerol composition is less than 1%; 2) traces of NaCl are present in the product but <0.1%; 3) the following additional preservatives and stabilizers are added—Glucose (20-30% w/w) and sodium benzoate (0.2-0.4% w/w).

[0045] The fermentation broth consists of water as well as sufficient nutrients required to enable cell growth. The fermentation broth also contains an anti-foam agent to control foaming in the fermentation.

[0046] A fermentor is partially filled to 65% of volumetric operating capacity with the components of the fermentation broth as well as 60% of the total glucose to be added. The glucose source is a starch hydrolysate of which 95% of the carbohydrates are glucose. The temperature is controlled at a value that is suitable for the fermentation host organism, in this case 34° C. The fermentor is then inoculated with a suitable fermentation microorganism, in this case, a yeast engineered for the production of lactic acid. The pH is maintained above 3.1 by the addition of calcium hydroxide.

[0047] As the fermentation proceeds, the glucose is converted into lactic acid at a certain yield. The glucose concentration is monitored by a near infrared spectroscopy system (NIR) (Brueker—Matrix F model). When the glucose has been reduced to less than 20 g/L as measured by NIR, the transglucosidase enzyme as described above is added at a dose of 0.025% (volume enzyme solution/volume fermentation broth).

[0048] The fermentation is then allowed to further proceed until the glucose concentration reaches 10 g/L. The remaining 40% of the total glucose is then gradually added to the fermentor at a rate controlled to maintain the glucose between 8 g/L and 12 g/L as measured by the NIR.

[0049] Once 100% of the target dextrose has been added, the glucose feed is stopped and the fermentation proceeds until the glucose is reduced below 0.5 g/L.

[0050] All patents, patent applications (including provisional applications), and publications cited herein are incorporated by reference as if individually incorporated for all purposes. Unless otherwise indicated, all parts and percentages are by weight and all molecular weights are weight average molecular weights. The foregoing detailed description has been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, for variations obvious to one skilled in the art will be included within the invention defined by the claims.