Non-sterile fermentation of bioethanol.
First Claim
1. An anti-bacterial composition comprising isolated and/or concentrated extracts from liquid fraction or wash waters of steam pretreated corn stover, wheat straw, rice straw, bagasse, corn fiber, empty fruit bunches or grass adapted for use in yeast fermentations of primarily starch biomass and effective against lactic acid bacteria.
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Abstract
A range of concentrations exists in which fermentation inhibitors derived from pretreatment of lignocellulosic feed stocks inhibit growth of lactic acid bacteria without affecting fermentive yeast. By optimizing levels of fermentation inhibitors to fall within this range, yeast fermentations of lignocellulosic biomass can be conducted under non-sterile conditions with ethanol yields comparable to those achieved under sterile conditions. Optimised inhibitor levels can be achieved by controlling the water/biomass ratio of a lignocellulosic biomass during and after pretreatment, for example by washing the fiber fraction of a previously pretreated lignocellulosic biomass with a pre-defined amount of fresh water or recycled process solutions. Crude extracts of liquid fraction or process solutions from pretreatment of lignocellulosic biomass can also provide an effective anti-bacterial treatment for first generation starch fermentations.
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Citations
19 Claims
- 1. An anti-bacterial composition comprising isolated and/or concentrated extracts from liquid fraction or wash waters of steam pretreated corn stover, wheat straw, rice straw, bagasse, corn fiber, empty fruit bunches or grass adapted for use in yeast fermentations of primarily starch biomass and effective against lactic acid bacteria.
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14. A method of yeast fermentation of starch biomass comprising the steps of
preparing a non-sterile yeast fermentation mixture comprising primarily starch biomass and optimised levels of fermentation inhibitors that inhibit contaminating bacterial growth and/or lactate production while having substantially no affect on ethanol fermentive yeast, and fermenting said fermentation mixture to produce ethanol, wherein optimised levels of fermentation inhibitors are achieved by addition of isolated and/or concentrated extracts from liquid fraction or wash waters of pretreated lignocellulosic biomass.
Specification