[Enhanced role of the co-culture of thermophilic anaerobic bacteria on cellulosic ethanol].
Fermentation of the type of cellulosic materials to ethanol was evaluated in batch system of mono-cultures of cellulolytic ethanol producing strains (Clostridium thermocellum strain LQRI), and co-cultures of LQRI in combination with one of the non-cellulolytic ethanol producing strains (Thermoanaerobacter pseudoethanolicus strains X514 or Thermoanaerobacter ethanolicus 39E). Results showed that ethanol yields and cellulose degradation abilities were significantly improved by the establishment of co-cultures consisting of LQRI and Thermoanaerobacter ethanolicus partner. A factorial experimental comparison revealed that the co-culture of LQRI + X514 provided the higher ethanol yield than the co-culture of LQRI + 39E, but no significant difference on cellulose degradation by LQRI was found in these co-cultures. In the absence of yeast extract, the highest ethanol concentrations in the co-cultures of LQRI + X514 and LQRI + 39E were about 71 mmol/L and 36.5 mmol/L, which were approximately 5-11 and 3-5 times higher than that of the mono-culture LQRI under the same concentration substrate, respectively. In the presence of 0.6% yeast extract, the highest ethanol concentrations in the co-cultures of LQRI + X514 and LQRI + 39E were rapidly improved and reached 263.5 mmol/L and 143.5 mmol/L, which were approximately 8-22 and 8-12 times higher than that of the mono-culture LQRI under the same concentrations substrate, respectively. The maximum ethanol concentration reached about 263.5 mmol/L (1.2%) in the co-culture of LQRI + X514 grown on 5% Solka Floc in the presence of 0.6% yeast extract, while the maximum ethanol concentration reached 143.5 mmol/L (1.2%) in the co-culture of LQRI + 39E grown on 2% Solka Floc in the presence of 0.6% yeast extract.
Fang
Zhi-guo
ZG
College of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, China. zhgfang77@yahoo.com.cn
D001421:Bacteria, Anaerobic / Q000254:growth & development / Q000378:metabolism; D002482:Cellulose / Q000737:chemistry / Q000378:metabolism*; D048013:Acetivibrio thermocellus / Q000254:growth & development* / Q000378:metabolism; D018920:Coculture Techniques; D000431:Ethanol / Q000032:analysis*; D005285:Fermentation; D046968:Thermoanaerobacter / Q000145:classification / Q000254:growth & development* / Q000378:metabolism; D015003:Yeasts / Q000378:metabolism
D000431:Ethanol; D002482:Cellulose