Tuesday, May 3, 2011
Lignocellulosic biomass is renewable, available at low cost, and exists in great abundance all over the world. This cellulosic biomass can be converted to fermentable sugars by different established pretreatment/hydrolysis processes. However, the hydrolysates of various cellulosic biomass all contain various amounts of five different sugars. Glucose and xylose predominate – followed by arabinose, mannose, and galactose. The efficient fermentation of all these sugars, particularly glucose and xylose, from such cellulosic biomass hydrolysates is necessary to economically produce cellulosic ethanol fuel. Naturally occurring Saccharomyces yeasts have proven to be the most effective microorganism for large-scale production of industrial ethanol from glucose-based feedstocks such as starch and cane sugar. However, the naturally occurring Saccharomyces yeasts cannot metabolize xylose and arabinose. Our currently best engineered yeast known as 424A(LNH-ST) has already been used by industry to produce cellulosic ethanol. Recently, we have made 424A(LNH-ST) able to ferment all five sugars, including arabinose, from any cellulosic biomass hydrolysates. Derivatives of 424A(LNH-ST) that can tolerate inhibitors such as acetic acid (strain 424A(LNH-ST)-AAR) or ethanol (strain 424A(LNH-ST)-ER) more effectively have also been developed. In this presentation, we will report the production of cellulosic ethanol using 424A(LNH-ST) and its further improved derivatives to ferment hydrolysates prepared from different sources - wheat straw, maple, mix southern hardwood, Arundo sp. and sorghum containing sugars ranging from 7 – 120 g/L for glucose and 45 – 80 g/L for xylose, and were provided by different companies.
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