高温厌氧细菌混合培养对纤维素酒精生产的提高作用

Enhanced Role of the Co-culture of Thermophilic Anaerobic Bacteria on Cellulosic Ethanol

以高温厌氧细菌热纤维梭菌(Clostridium thermocellum LQRI)和嗜热厌氧乙醇菌(Thermoanaerobacter ethanolicus X514和Thermoanaerobacter pseudoethanolicus39E)为对象,以纤维素为微生物利用的底物,分析了LQRI纯培养和LQRI+Thermoanaerobacter混合培养对纤维素降解、酒精生产及终产物分布的影响.结果表明,LQRI+Thermoanaerobacter混合培养的酒精生产能力和纤维素降解率明显高于LQRI纯培养.在混合培养体系中,LQRI+X514的酒精生产能力明显高于LQRI+39E.培养基中无外源酵母粉条件下,LQRI纯培养酒精最高浓度约为11.5mmol/L,LQRI+X514和LQRI+39E混合培养最高酒精浓度分别约为71mmol/L和36.5mmol/L,相同的底物纤维素浓度条件LQRI+X514和LQRI+39E混合培养酒精浓度分别约为LQRI纯培养的5～11倍和3～5倍,纤维素降解率分别都约为LQRI纯培养的1.5～5.0倍;培养基中0.6%外源酵母粉存在条件下,LQRI纯培养酒精最高浓度约为12.9mmol/L,LQRI+X514和LQRI+39E混合培养最高酒精浓度分别约为263.5mmol/L和143.5mmol/L,相同的底物纤维素浓度条件LQRI+X514和LQRI+39E混合培养酒精浓度分别约为LQRI纯培养的8～22倍和8～12倍,纤维素降解率均约为LQRI纯培养的1.1倍.在5%Solka Floc为底物和0.6%外源酵母粉的条件下,LQRI+X514混合培养酒精浓度最高可达到263.5mmol/L,相当于1.2%(质量浓度)的酒精,LQRI+39E约为143mmol/L.

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.