Mai, Duong Thai (2017-01). Chemical Treatment of Lignocellulosic Biomass using Ionic Liquid and the Development of a Compatible Hyper-Tolerant Bacterial Strain for Lipid Production. Master's Thesis.
Thesis
Lignocellulosic biomass is an abundant and potentially valuable source of organic substrate for biofuel-producing microorganisms. Various physical, chemical, and biological treatment methods have been established to alleviate the recalcitrance of lignocellulose for substrate utilization. The objective of this study is to evaluate the potential of another chemical treatment method, utilizing an ionic liquid [Emim][Cl] pretreatment coupled with dilute acid treatment, to convert spent coffee grounds, corn husk, and bermuda grass into fermentable sugars. The second objective was to develop a highly tolerant bacterium to minimize the need for detoxification. Fermentable sugar yields were quantified and compared to enzymatic treatment methods. Results indicated that the chemical treatment method was able to produce sufficient sugar yields to be considered a prospective alternative to enzymatic hydrolysis. R. opacus PD630 was able to utilize the sugar released from this chemical treatment for growth. Additionally, a compatible hyper-tolerant strain PD630V4 was developed using an adaptive evolution approach. Inhibitory concentrations were quantified for the PD630 and used as an adaption benchmark. The adapted strain was capable of growth on inhibitory levels of pH, [Emim][Cl], and HMF. Moreover, PD630^V4 strain showed significantly less inhibition than the wild-type strain on crude hydrolysate. The PD630^V4 strain was capable of reaching stationary phase and accumulating lipids in approximately 5 days when cultivated in the crude spent coffee grounds, corn husk, and grass hydrolysates.
