Sunday, May 4, 2008
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Phanerochaete chrysosporium Conditioning of Grasses: Enzyme Activity and Hydrolysis to Sugars

Swetha Mahalaxmi1, Collin R. Jackson2, and Clint Williford1. (1) Chemical Engineering, University of Mississippi, P.O. Box 1848, University, MS 38677, (2) Department of Biology, University of Mississippi, University, MS 38677

Biomass recalcitrance to hydrolysis to sugars remains a key barrier to economic cellulosic ethanol production. Our goal is to use microbial conditioning of lignocellulosic feedstock, reducing recalcitrance, and facilitating improved performance and/or reducing required severity of downstream pretreatment. Accordingly, we conditioned cornstover, switchgrass, miscanthus and sorghum with Phanerochaete chrysosporium. Ten grams of each feedstock was inoculated in 250 ml flasks and incubated for 28 days at 28⁰C. We conducted enzyme assays every 7 days from the initial day to the 28th day. The assays measured activities for phenol oxidase, peroxidase, β-glucosidase, β-xylosidase and cellobiohydrolase during the course of conditioning. After incubation, we conducted a compositional analysis, as well as a 72 hour enzymatic hydrolysis using Novozyme 188 and Spezyme CP at 50⁰C, assessing changes in recalcitrance to conversion to sugars. During the 28 day conditioning, P. chrysosporium   produced significant activities for β-glucosidase, β-xylosidase and cellobiohydrolase enzymes. It did not produce any activity for phenol oxidase and peroxidase enzymes. The observed activities reached maximum levels on or about the 7th day for almost all the four biomasses. The enzyme activity profiles suggest an apt period of conditioning for the respective feedstocks based on the highest enzymatic activity. A comparison of changes in enzymatic hydrolysis to sugars (conversion) is made among the four feedstocks.

 


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