Mushroom Inoculation on Switchgrass Feedstock during Storage: Effects of Subsequent Pre-processing for Intended Biofuels Production

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Turay, Amandeep Singh
Agronomy and Crop Sciences; Biological Engineering; Plant Biology
thesis / dissertation description
The objective of this project was to examine the effect of fungal treatment and liquid hot water pretreatment of switchgrass combine in view of increasing glucose release. The fungal treatment consisted of incubating Pleurotus ostreatus in square switchgrass bales, at 50% moisture content for 25 days, 54 days, and 82 days. The digestibility of the switchgrass biomass was subsequently evaluated using Accelerase 1500 enzyme. Lignin is an important barrier to enzymatic hydrolysis, and it was stipulated that incubation with P. ostreatus would disrupt plant cell walls, resulting in enhanced saccharification. Three different concentrations of P. ostreatus were evaluated: 0%, 2%, and 3% by weight. Maximum digestibility was observed in switchgrass pretreated with 3% P. ostreatus for 25 days but not yet pretreated in hot water, which resulted in 39% saccharification as opposed to 32% with that of 0% P. ostreatus. This indicated that the fungal inoculation facilitated structural carbohydrate release. Switchgrass samples collected after solid state fermentation with P. ostreatus were subjected to liquid hot water (LHW) pretreatment at 200°C for 10 min, and 180°C for 30 min, and the prehydrolyzates were washed with 5X volumes of water, before being used for enzymatic analysis. Overall, LHW pretreatment enhanced the enzymatic digestibility of fungal fermented switchgrass. For fermented switchgrass samples pretreated using LHW, at 200°C for 10 min, maximum saccharification of 82% was obtained for the samples inoculated with 3% P. ostreatus and stored for 82 days. However, there were no significant differences between the other conditions. Enzymatic hydrolysis was also performed for the washed LHW pretreated switchgrass samples. Washing prehydrolyzates after LHW pretreatment was supposed to enhance its enzymatic digestibility; however in this study, a significant overall reduction in enzymatic digestibility was observed as compared to the non-washed samples.