Tuesday, February 10, 2015
1:10 PM, 2045 Bainer Hall
Topic: "A novel biochemical route for fuels and chemicals production from cellulosic biomass"
Speaker: Zhiliang (Julia) Fan, Assistant Professor
Department of Biological and Agricultural Engineering
University of California, Davis
One significant obstacle impeding the large scale production of fuels and chemicals from cellulosic biomass is the lack of a low cost processing technology. The conventional biochemical platform for biorefinery involves five distinct steps: pretreatment, enzymatic hydrolysis, fermentation, and product recovery. Sugars are produced as the reactive intermediate for the subsequent fermentation. Steps involved with overcoming the recalcitrance of cellulosic biomass (pretreatment, cellulase production, and enzymatic hydrolysis) are the three most costly steps in the whole process. Here we propose a novel biochemical route for fuels and chemical production that will replace the two most costly steps in the conventional platform with a single biological step. Cellulolytic microorganism(s) that can secrete all the enzymes needed to hydrolyze cellulose and hemicellulose will be modified to convert most of the carbohydrate contained in the cellulosic biomass to sugar aldonates. In a second step, sugar aldonates will be utilized as the carbon source to produce ethanol and other products. The new route can potentially lower the cost of cellulosic bioprocessing substantially. Our study has revealed that about 79% of the cellulose can be diverted to cellobiose and cellobionate production using a engineered Neurospora crassa strain. Exogenously addition of laccase and redox mediator further improved the yield of cellobionate from cellulose to 91%. Both of the hydrolysis product of cellobionate (glucose and gluconate) can be fermented to ethanol by an engineered Escherichia coli strain. Gluconate was utilized even faster than that of glucose. Deletion of the competing pathway in E. coli improved the ethanol yield from gluconate.
Coffee and cookies will be served.