A Novel Biochemical Platform for Fuels and Chemicals Production Through Sugar Aldonates As the Reactive Intermediates: Process Optimization

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 platform 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 in spite of the presence of lignin 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. We aim to develop the new platform using the conversion of the cellulose contained in the cellulosic biomass to ethanol as the model system and using Neurospora crass as the model microorganism.   Cellobionate is produced as the reactive intermediate for ethanol production. The new platform can potentially lower the cost of cellulosic bioprocessing substantially. This study we report the enhancement of the cellobionate production by knocking down more copies of b-glucosidase and over-expressing cellobiose dehydrogenase.