Optimization of bioconversion of green waste to sugar for ethanol production

• Main Author: Ng, Bernard Jia Han.
• Other Authors: Wang Jing-Yuan
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Environmental engineering::Waste management
• Online Access: http://hdl.handle.net/10356/39646
• Institution: Nanyang Technological University

Ethanol production from green waste can be useful in helping solve the current energy crisis, food crisis and climate change. During the bioconversion process, enzymatic hydrolysis, which converts hemicelluloses and celluloses to reducing sugar, was focused on. Hence, the fermentation of reducing sugar to ethanol is more easily carried out once high reducing sugar yield is obtained. Previous studies had identified and isolated seven major strains of bacteria or fungi which existed naturally in a stable indigenous microbial community in high sugar yields. 127 possible combinations were tested to identify the group with the highest reducing sugar yield. The best microbial combination 1345 is comprised of Microbacterium sp., Tsukamurella sp., Pseudallescheria sp., and Bacillus sp.. The bioconversion effectiveness of this optimal microbial combination was further investigated by adjusting pH value, temperature, initial carbon concentration, and pretreatment methods. Overall, Organosolv process performed better than Liquid Hot-Water pretreatment. 25g/L Organosolv-pretreated lignocelluloses with 45°C and pH 7.5 environments showed the best relative reducing sugar yield, 9.5g/L at 24-hour. Result analysis shows that microbial community 1345 may perform better under pH 6.0, 60°C and 25g/L initial carbon concentration. Among all the factors, initial carbon concentration is the limiting factor.