Gomez-Flores Maritza, Nakhla George, Hafez Hisham
Department of Chemical and Biochemical Engineering, Faculty of Engineering, University of Western Ontario, London, ON, N6A 5B9, Canada.
Department of Civil and Environmental Engineering, Faculty of Engineering, University of Western Ontario, London, ON, N6A 5B9, Canada.
AMB Express. 2017 Dec;7(1):84. doi: 10.1186/s13568-016-0256-2. Epub 2017 Apr 20.
Cellulose utilization by hydrogen producers remains an issue due to the low hydrogen yields reported and the pretreatment of cellulose prior to fermentation requires complex and expensive steps. Clostridium termitidis is able to breakdown cellulose into glucose and produce hydrogen. On the other hand, Clostridium beijerinckii is not able to degrade cellulose but is adept at hydrogen production from glucose; therefore, it was chosen to potentially enhance hydrogen production when co-cultured with C. termitidis on cellulose. In this study, batch fermentation tests were conducted to investigate the direct hydrogen production enhancement of mesophilic cellulolytic bacteria C. termitidis co-cultured with mesophilic hydrogen producer C. beijerinckii on cellulose at 2 g l compared to C. termitidis mono-culture. Microbial kinetics parameters were determined by modeling in MATLAB. The achieved highest hydrogen yield was 1.92 mol hydrogen mol hexose equivalent in the co-culture compared to 1.45 mol hydrogen mol hexose equivalent in the mono-culture. The maximum hydrogen production rate of 26 ml d was achieved in the co-culture. Co-culture exhibited an overall 32 % enhancement of hydrogen yield based on hexose equivalent added and 15 % more substrate utilization. The main metabolites were acetate, ethanol, lactate, and formate in the mono-culture, with also butyrate in the co-culture. Additionally, the hydrogen yield of C. beijerinckii only in glucose was 2.54 mol hydrogen mol hexose equivalent. This study has proved the viability of co-culture of C. termitidis with C. beijerinckii for hydrogen production directly from a complex substrate like cellulose under mesophilic conditions.
由于所报道的氢气产量较低，氢气生产者对纤维素的利用仍然是一个问题，并且在发酵之前对纤维素进行预处理需要复杂且昂贵的步骤。白蚁梭菌能够将纤维素分解为葡萄糖并产生氢气。另一方面，拜氏梭菌不能降解纤维素，但擅长从葡萄糖产生氢气；因此，当与白蚁梭菌在纤维素上共培养时，它被选择用于潜在地提高氢气产量。在本研究中，进行了分批发酵试验，以研究嗜温纤维素分解菌白蚁梭菌与嗜温氢气生产者拜氏梭菌在2 g/l纤维素上共培养相比于白蚁梭菌单培养时直接提高氢气产量的情况。通过在MATLAB中建模确定微生物动力学参数。共培养中实现的最高氢气产量为1.92摩尔氢气/摩尔己糖当量，而单培养中为1.45摩尔氢气/摩尔己糖当量。共培养中实现的最大氢气产生速率为26毫升/天。基于添加的己糖当量，共培养显示氢气产量总体提高了32%，底物利用率提高了15%。单培养中的主要代谢产物是乙酸盐、乙醇、乳酸盐和甲酸盐，但共培养中还有丁酸盐。此外，拜氏梭菌仅在葡萄糖中的氢气产量为2.54摩尔氢气/摩尔己糖当量。本研究证明了在嗜温条件下，白蚁梭菌与拜氏梭菌共培养直接从纤维素等复杂底物生产氢气的可行性。
