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Title: Understanding Free and Complexed Enzyme Mechanisms and Factors Contributing to Cell Wall Recalcitrance (Presentation)

Fungal free enzymes and bacterial complexed cellulosomes deconstruct biomass using different physical mechanisms. Free enzymes, which typically contain a large proportion of GH7 cellobiohydrolase, diffuse throughout the substrate and hydrolyze primarily from the cellulose reducing end, resulting in 'sharpened' macrofibrils. In contrast, complexed cellulosomes contain a diverse array of carbohydrate binding modules and multiple catalytic specificities leading to delamination and physical peeling of the cellulose macrofibril structures. To investigate how cellulose structure contributes to recalcitrance, we compared the deconstruction of cellulose I, II, and III; using free and complexed enzyme systems. We also evaluated both systems on Clean Fractionation and alkaline pretreated biomass, which remove much of the lignin, to determine the impact on enzyme loading reduction. Free fungal enzymes demonstrated a swelling of the outer surface of the plant cell walls while removing localized disruptions, resulting in a smooth surface appearance. Cellulosomes produced cell wall surfaces with localized areas of disruption and little surface layer swelling. These studies contribute to the overall understanding of biomass recalcitrance and how combining different enzymatic paradigms may lead to the formulation of new enzyme cocktails to reduce the cost of producing sugars from plant cell wall carbohydrates.
Authors:
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Publication Date:
OSTI Identifier:
1168770
Report Number(s):
NREL/PR-2700-60927
DOE Contract Number:
AC36-08GO28308
Resource Type:
Conference
Resource Relation:
Conference: Presented at the 36th Symposium on Biotechnology for Fuels and Chemicals, 28 April-1 May 2014, Clearwater Beach, Florida; Related Information: NREL (National Renewable Energy Laboratory)
Research Org:
National Renewable Energy Laboratory (NREL), Golden, CO.
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy Bioenergy Technologies Office
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; 59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CELLULASE; BIOFUELS; LIGNIN; CELLULOSE; MICROSCOPY; SACCHARIFICATION CELLULASES; BIOFUELS; CELLULOSOME; LIGNIN; CELLULOSE; MICROSCOPY; ORGANOSOLV; CLEAN FRACTIONATION; ; SACCHARIFICATION; PRETREATMENT