Semester

Spring

Date of Graduation

2011

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Forest Resource Management

Committee Chair

Benjamin Dawson-Andoh

Abstract

Recalcitrance of lignocellulosic cell wall is a major hurdle that needs to be disrupted for biochemical refinery to be successful. Pretreatment of lignocellulosic materials play a key role for the conversion of lignocellulosic feed stocks to fermentable sugars. At present, various pretreatment technologies mainly achieved by empirical methods are available for the production of sugars from lignocellulosic polysaccharides. These methods depend largely upon the "demolition" of the cell wall by strong chemicals or using high energy input. As a result, these processes release "smaller compounds" as by-products or end products which inhibits downstream fermentation of monomeric sugars.;This project is a preliminary study to understand the combined effect of mechanical action and enzyme hydrolysis on the yield of sugars from two lignocellulosic biomass viz, hard maple (Acer saccharum Marsh.) and corn stover (Zea mays L.). The mechanical treatment involves wet attrition milling and the application electron beams. The enzyme treatments are done by using six cell wall depolymerizing enzymes. The amounts of total sugars release after each treatment are measured by Dinitrosalicylic acid (DNS) assay and types of sugars release were determined by High Performance Liquid Chromatography (HPLC) analysis. Particle size were measured by Microtract particle size analyzer and also by image analysis. Treatments that required minimum number of enzymes to produce significantly higher amount of sugars were selected for the studying the effect of increased enzyme concentration on the amount of sugars released. Further, the residues from enzyme hydrolysis are analyzed by ATR-FTIR and NMR to understand the degree of depolymerization of cell wall biopolymers. Depolymerizing properties of electron beams on corn stover particulates were also studied. The effects of irradiation on these specimens were evaluated by estimating the amount of total sugars released after the treatment with AccelleraseRTM 1000.;This study has shown that the enzymatic digestibility of a pretreated hard maple and corn stover are enhanced by reducing the particle size. A significant increase in the yield of sugars were also observed in the treatments that were pretreated with CDTA (1,2-Cyclohexylenedi nitrilo-tetraacetic Acid) and BSA (Bovine Serum Albumin). Presence of glucose and xylose were confirmed by HPLC (High Performance Liquid Chromatography) analysis. Lower sugar yields were measured after the treatment corn stover with electron beams. Future studies are required to understand the effect of the sequence of the enzymes for a higher sugar yield and also to combine other pretreatment methods with electron beams for a better deconstruction of lignocellulosic cell wall.

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