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ARS Home » Southeast Area » Tifton, Georgia » Crop Genetics and Breeding Research » Research » Publications at this Location » Publication #165698
Title: ENZYME-PRETREATMENT OF GRASS LIGNOCELLULOSE FOR POTENTIAL HIGH-VALUE CO-PRODUCTS AND AN IMPROVED FERMENTABLE SUBSTRATE

Author
item Anderson, William - Bill
item PETERSON, JOY - UNIV OF GA
item Akin, Danny
item Morrison Iii, Wiley

Submitted to: Applied Biochemistry and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2005
Publication Date: 5/1/2005
Citation: Anderson, W.F., Peterson, J., Akin, D.E., Morrison Iii, W.H. 2005. Enzyme-pretreatment of grass lignocellulose for potential high-value co-products and an improved fermentable substrate. Applied Biochemistry and Biotechnology. 121-124:303-310.

Interpretive Summary: Cell walls of plants are composed of a number of complex carbohydrate molecules, including lignocellulose. Lignocelluloses of grasses, which comprise the majority of the dry weight, are potential sources of biofuel to expand the bioethanol industry currently based on corn grain. While crop biomass yield is high for grasses, aromatic compounds released from the lignocelluloses during chemical breakdown of the cell wall material, reduce substrates suitable for fermentation. These aromatic compounds are diverse, existing as large interconnecting molecules called lignins of various types and also as the phenolic acids, i.e., ferulic and p-coumaric, that are bonded to cellulose and other carbohydrates. Research has been conducted to locate and identify the various types of aromatics within grass lignocellulose and to rank their role in limiting degradation of the cell wall material into fermentable sugar molecules. Enzyme pretreatments may provide environmentally friendly methods for release of phenolic acids from lignocellulose to be used in industry as a high-value co-product while improving fermentation of the residue to ethanol. Preliminary research using a commercial esterase enzyme showed that these useful compounds are released more efficiently than previous methods. The most appropriate varieties of forage grasses were identified for pretreatment with these esterase enzymes by comparing amounts obtained in the laboratory. The residue from the pretreatments was then subjected to cellulase to produce sugars, form cellulose which are then used in fermentation to produce ethanol for fuel use. Tifton 85 bermudagrass and elephantgrass were fermented to alcohol most efficiently.

Technical Abstract: Lignocelluloses of grasses are potential sources of biofuel to expand the bioethanol industry currently based on corn grain. While crop biomass yield is high for grasses, aromatics in the lignocelluloses impede hydrolysis of cell wall polysaccharides and reduce substrates suitable for fermentation. These aromatics are diverse, existing as recalcitrant lignins (phenylpropanoids) of various types and also as the phenolic acids, i.e., ferulic and p-coumaric, that are ester-linked to carbohydrates. Research has been conducted to locate and identify the various types of aromatics within grass lignocellulose and to rank their role in recalcitrance to biodegradation. Enzyme pretreatment strategies may provide environmentally friendly methods for release of phenolic acids from lignocellulose for a potentially high-value co-product while improving fermentability of the residue. Preliminary research using a commercial ferulic acid esterase, before saccharification with cellulase, showed a substantial increase in supernatant ferulic and p-coumaric acids, arabinose, xylose, and cellulose over cellulase treatment alone. The most appropriate cultivars of grasses were identified for pretreatment with esterases and initial results on the fermentation of enzyme-pretreated grass lignocellulose indicated potential improvements in fermentation over non-esterase treated grasses.