Co-fermentation of hexose and pentose sugars simulating lignocellulosic hydrolysates for bio-ethanol production | |
| Author | Luu Huyen Trang |
| Call Number | AIT Thesis no.FB-10-29 |
| Subject(s) | Fermentation Ethanol as fuel |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Food Engineering and Bioprocess Technology, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. no.FB-10-29 |
| Abstract | The search for alternative liquid fuels has led to extensive research on non-food lignocellulosic biomass as an alternative source of energy. This study is an attempt to effectively convert all fermentable sugars present in lignocellulosic hydrolysates (hexoses and pentoses) using co-culture systems in which more than one fermentive microorganism was used in the fermentation process. In this study, immobilized cells of Z.mobilis DSM 424 and free cells of P.stipitis DSM 3651 were simultaneously employed in a co-fermentation process to efficiently convert a synthetic sugar mixture to ethanol. A sugar mixture of 50 g/L of glucose, xylose, mannose, galactose and arabinose was converted to 18.67 g ethanol with a volumetric production rate of 0.78 g/L/h in 24 hours, giving a yield of 0.44 g/g. It is believed that the co-culture of immobilized Z.mobilis and P.stipitis for the conversion of a defined mixture of five reducing sugars in the range they are present in such hydrolysates in this study is the first reported so far. Z.mobilis free cells were found to have suppressive effects on P.stipitis cell growth and fermentive performance and the immobilization of the bacterium has proved to completely reduce these effects in the co-culture system. The effect of fufural and HMF, two common compounds in such hydrolysates that inhibit ethanol fermentation, was also studied. Furfural at the concentration of 2 g/L was found to have great inhibitory effects on microbial cell activities. Almost no cell growth of P.stipitis was observed during the first 24 hours of fermentation and only 0.27 g/g ethanol yield was obtained at this concentration. HMF was found to have less detrimental effects at the same concentration. Overall, the results indicate that a co-cultured immobilized system of microorganisms could effectively convert lignocellulosics to ethanol with high yields. |
| Year | 2010 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. no.FB-10-29 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Rakshit, Sudip Kumar; |
| Examination Committee(s) | Athapol Noomhorm;Anal, Anil Kumar; |
| Scholarship Donor(s) | Deutscher Akademischer Austausch Dienst; |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 2010 |