Biofuels and Co-Products Generation Using Modified Yeast and Bacteria.

Abstract

Softwood is a major source of lignocellulosic biomass and contains about 44% cellulose, 22% hemicellulose and 28% lignin (dry wt basis). Pulp and paper industries have used softwood for a variety of paperand packaging products. Many in this industry are now transitioning to more of a biorefinery by producing fuels and other bioproducts as well. Coupling current industrial processes with new biofuels and biomaterials prodn. could enhance economic and environmental sustainability. Industries could also build in flexibility to convert the total biomass to fuels and products. Conversion of softwood to ethanol is challenging due to high lignin and extractables content. Problematic compds. also result from chem. pretreatments designed to break down the plant cell wall in softwoods. Compds. potentially inhibitory to microorganisms include: furfural, 5-hydroxymethylfurfural (HMF), levulinic acid, acetic acid, formic acid, uronic acid, 4-hydroxybenzoic acid, vanillic acid, vanillin, phenol, cinnamaldehyde, formaldehyde 2-furoic acid, 3,4-dihydroxybenzoic acid, 3,4-dihydroxybenzaldehyde, salicylic acid, homovanillic acid, benzoic acid, and ferulic acid. Using com. available ethanologenic yeasts with increasing solids concns. of pretreated pine resulted in increased lag times. A modified yeast, AJP50, has recently been developed for fermn. of softwood biomass at high solids concns. AJP50 reached over 40 g/L ethanol after 72 h in 17.5% w/v solids fermns. At the same inoculum level, the parent strain only produced 7 g ethanol/L after 72 h of fermn. With a 100X increase in inoculum, the parent produced 18 g ethanol/L by 72 h and 40 g ethanol/L by 144h fermn. In contrast, AJP 50 produced 95-85% of max. theor. yield (MTY) of ethanol by 48h fermn. in 12-15% w/v solids of pine subjected to a harsher pretreatment. The parent yeast was unable to survive in the more severely pretreated pine at the same inoculum level. Adding an addnl. biocatalyst able to producevalue-added compds. during fermn. also improved the economic feasibility of the pine-to-biofuel process. [on SciFinder(R)]