Enhanced efficiency ethanol and sugar conversion processes
First Claim
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1. A process for producing ethanol by the fermentation of biomass containing carbohydrate comprising:
- a. hydrolyzing an admixture of water, enzyme and biomass under hydrolyzing conditions sufficient to convert carbohydrate by enzymatic hydrolysis and provide a hydrolysate containing pentose and hexose;
b. subjecting at least a portion of the hydrolysate of step (a) to fermentation conditions sufficient to convert at least a portion of the hexose to ethanol to provide an ethanol-containing fermentation broth containing solids and pentose, said fermentation conditions comprising the presence of microorganism capable of converting hexose to ethanol, and said ethanol-containing fermentation broth containing solids;
c. fractionating by distillation at least a portion of the ethanol-containing fermentation broth of step (b) to provide an ethanol product fraction and a whole stillage containing water, solids and unfermented sugars comprising pentose;
d. separating at least a portion of the whole stillage of step (c) to provide a thin stillage containing pentose and having an essential absence of solids and to provide a solids-containing fraction;
e. contacting under fermentation conditions in a fermentation zone at least a portion of the thin stillage of step (d) with biocatalyst said biocatalyst comprising;
i. a solid structure of hydrated hydrophilic polymer defining an interior structure having a plurality of interconnected major cavities having a smallest dimension of between about 5 and 100 microns and a Hydration Expansion Volume (HEV), which is calculated in volume percent, of about 1000 or more, andii. a population of microorganisms capable of converting pentose to ethanol substantially irreversibly retained in the interior of the solid structure, said population of microorganisms being in a concentration of about 60 grams per liter or more based upon the volume defined by the exterior of the solid structure when fully hydrated, to provide a treated thin stillage having a reduced pentose content and substantially no solids;
f. withdrawing the treated thin stillage from the fermentation zone of step (e) while retaining the biocatalyst in the fermentation zone;
g. evaporating water and ethanol from at least a portion of the treated thin stillage of step (f) to provide a concentrated solubles product and vapor; and
h. passing at least a portion of the evaporated water and ethanol of step (g) to step (a).
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Abstract
Overlay processes are disclosed for making ethanol that not only increase ethanol conversion but do so in a cost effective manner with a reduction in energy requirements per unit of ethanol production. The processes can provide, if desired, higher organic compound as a co-product with ethanol.
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Citations
5 Claims
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1. A process for producing ethanol by the fermentation of biomass containing carbohydrate comprising:
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a. hydrolyzing an admixture of water, enzyme and biomass under hydrolyzing conditions sufficient to convert carbohydrate by enzymatic hydrolysis and provide a hydrolysate containing pentose and hexose; b. subjecting at least a portion of the hydrolysate of step (a) to fermentation conditions sufficient to convert at least a portion of the hexose to ethanol to provide an ethanol-containing fermentation broth containing solids and pentose, said fermentation conditions comprising the presence of microorganism capable of converting hexose to ethanol, and said ethanol-containing fermentation broth containing solids; c. fractionating by distillation at least a portion of the ethanol-containing fermentation broth of step (b) to provide an ethanol product fraction and a whole stillage containing water, solids and unfermented sugars comprising pentose; d. separating at least a portion of the whole stillage of step (c) to provide a thin stillage containing pentose and having an essential absence of solids and to provide a solids-containing fraction; e. contacting under fermentation conditions in a fermentation zone at least a portion of the thin stillage of step (d) with biocatalyst said biocatalyst comprising; i. a solid structure of hydrated hydrophilic polymer defining an interior structure having a plurality of interconnected major cavities having a smallest dimension of between about 5 and 100 microns and a Hydration Expansion Volume (HEV), which is calculated in volume percent, of about 1000 or more, and ii. a population of microorganisms capable of converting pentose to ethanol substantially irreversibly retained in the interior of the solid structure, said population of microorganisms being in a concentration of about 60 grams per liter or more based upon the volume defined by the exterior of the solid structure when fully hydrated, to provide a treated thin stillage having a reduced pentose content and substantially no solids; f. withdrawing the treated thin stillage from the fermentation zone of step (e) while retaining the biocatalyst in the fermentation zone; g. evaporating water and ethanol from at least a portion of the treated thin stillage of step (f) to provide a concentrated solubles product and vapor; and h. passing at least a portion of the evaporated water and ethanol of step (g) to step (a). - View Dependent Claims (2, 3, 4, 5)
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Specification