嗜热厌氧菌发酵甘蔗渣产氢及产乙醇研究

发布时间：2018-03-13 07:48

本文选题：嗜热厌氧菌　切入点：甘蔗渣　出处：《华南理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着人类对能源需求量的急剧增长,化石能源的短缺,加之化石燃料燃烧引发的一系列日益凸显的环境问题,寻求可替代的可再生清洁能源已成为国际热点议题。生物质能(如氢气和乙醇)以其清洁、高效和可再生的特点,被视为21世纪最具发展潜力的新兴能源。利用地球上含量丰富的木质纤维素生产生物质能越来越受到世界各国的高度重视。本研究利用嗜热厌氧梭菌(Clostridium thermocellum ATCC 27405)和嗜热厌氧杆菌(Thermoanaerobacterium aotearoense SCUT27/Δldh)介导的生物降解体系,从以下几个方面研究甘蔗渣降解产氢及产乙醇:1)CaCO_3强化嗜热厌氧菌降解甘蔗渣产氢及产乙醇并进行机理初探;2)pH控制对C.thermocellum降解甘蔗渣产氢影响;3)CaCO_3和非离子表面活性剂Triton X-100强化嗜热厌氧菌降解甘蔗渣。CaCO_3可强化嗜热厌氧菌发酵甘蔗渣产氢及产乙醇,通过对发酵工艺的优化,以2%预处理后的甘蔗渣为发酵底物,CaCO_3添加浓度为20 mM,利用C.thermocellum进行嗜热厌氧发酵。氢气产量最高达到97.83±5.19 mmol/L,与不添加CaCO_3对照组相比提高了116.72%。与添加CaCO_3条件下的C.thermocellum单培养体系相比,C.thermocellum和T.aotearoense共培养体系虽然在产氢方面没有明显优势,但乙醇产量有明显提高。在最适发酵条件下,乙醇产量达到10.60±0.81 mM,与不添加CaCO_3的对照组相比提高了192.82%。CaCO_3对发酵液pH具有缓冲作用是其强化嗜热厌氧菌降解甘蔗渣的重要原因。在500 m L机械搅拌式生物反应器中研究了恒定pH控制和两阶段pH控制对C.thermocellum发酵产氢影响,发现pH控制方式对C.thermocellum发酵产氢有显著影响:C.thermocellum发酵产氢的最适pH为6.0左右;在C.thermocellum代谢过程中,氢气和发酵液中代谢产物(主要为乙醇和乙酸等有机酸)的生成存在竞争关系,两者产量存在此消彼长的关系;两阶段pH控制方式不能进一步有效促进C.thermocellum发酵产氢。CaCO_3和非离子表面活性剂Triton X-100可共同强化嗜热厌氧菌降解甘蔗渣,通过发酵条件的优化,发酵液中的还原糖总量最高可达14.07±0.67 g/L。非离子表面活性剂Triton X-100对嗜热厌氧菌具有毒害作用,会导致嗜热厌氧菌代谢终止,但表面活性剂可提高发酵液中羧甲基纤维素酶活力、木聚糖酶活力和β-葡萄糖苷酶活力,从而提高对甘蔗渣的水解效率。本研究一方面借助廉价易得的CaCO_3强化嗜热厌氧菌降解甘蔗渣产氢及产乙醇,为利用CBP途径生产生物质能提供了行之有效的方法;另一方面借助CaCO_3和非离子表面活性剂Triton X-100实现由嗜热厌氧菌介导的生物降解体系对甘蔗渣的生物糖化,进而进行后续的乙醇发酵,为未来木质纤维素的能源化提供了新思路。
[Abstract]:With the rapid growth of human demand for energy, the shortage of fossil energy, and a series of increasingly prominent environmental problems caused by fossil fuel combustion, The search for alternative renewable and clean energy has become an international hot topic. Biomass energy (such as hydrogen and ethanol) is characterized by its cleanliness, efficiency and renewability, In 21th century, it is regarded as the most potential new energy source. The production of biomass energy by using the abundant lignocellulose on the earth has been paid more and more attention in the world. In this study, we used Clostridium thermocellum ATCC 27405) and. The biodegradation system mediated by Thermoanaeracterium aotearoense SCUT27/ 螖 ldh. Study on the effect of pH Control on hydrogen production of bagasse degradation by bagasse and ethanol production by Alcohol 1 CaCO3 from bagasse degradation and ethanol production by thermophilic anaerobic bacteria and its mechanism on C. thermocellum degradation of bagasse and its effects on Caco _ 3 and Nonionic Surfactant. Triton X-100 enhanced thermophilic anaerobic degradation of bagasse. CaCOST3 enhanced thermophilic anaerobic fermentation of bagasse to produce hydrogen and ethanol. By optimizing the fermentation process, After 2% pretreatment of bagasse as fermentation substrate, the concentration of CaCO3 was 20 mm, and the thermophilic anaerobic fermentation was carried out by using C. thermocellum. The hydrogen production reached the maximum of 97.83 卤5.19 mmol / L, which increased 116.72% compared with the control group without CaCO_3. Compared with C. thermocellum monoculture under the condition of adding CaCO_3, the hydrogen production reached a maximum of 97.83 卤5.19 mmol / L, which was 116.72% higher than that of the control group without adding CaCO_3. Compared with C. thermocellum and T. aotearoense co-culture system, the culture system had no obvious advantage in hydrogen production. But the yield of ethanol increased obviously. Under the optimum fermentation conditions, Ethanol production reached 10.60 卤0.81 mm, which increased the pH of fermentation broth by 192.82% compared with the control group without CaCO_3. The important reason for its enhanced thermophilic anaerobic degradation of bagasse was found in 500ml mechanically stirred bioreactor. The effects of constant pH control and two-stage pH control on hydrogen production by C. thermocellum fermentation were investigated. It was found that pH control mode had a significant effect on hydrogen production by C. thermocellum fermentation. The optimum pH for hydrogen production was about 6.0. During the metabolism of C. thermocellum, there was a competitive relationship between the production of hydrogen and metabolites (mainly organic acids such as ethanol and acetic acid) in C. thermocellum fermentation. The two-stage pH control mode could not further promote the fermentation of C. thermocellum to produce hydrogen. CaCOS3 and Nonionic surfactant Triton X-100 could enhance the degradation of bagasse by thermophilic anaerobes and optimize the fermentation conditions. The total amount of reducing sugar in fermentation broth was up to 14.07 卤0.67 g / L. Nonionic surfactant Triton X-100 had toxic effect on thermophilic anaerobes, which would lead to the termination of thermophilic anaerobes metabolism, but surfactant could increase the activity of carboxymethyl cellulase in fermentation broth. Xylanase activity and 尾-glucosidase activity improved the hydrolysis efficiency of bagasse. On the one hand, the thermophilic anaerobic bacteria were used to enhance the degradation of hydrogen and ethanol from bagasse by cheap and easily available CaCO_3. It provides an effective method for the production of biomass energy by CBP pathway, and on the other hand, realizes the bio-saccharification of bagasse by thermophilic anaerobic-mediated biodegradation system with CaCO_3 and Nonionic surfactant Triton X-100. The subsequent ethanol fermentation provides a new idea for the energy conversion of lignocellulose in the future.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ116.2;TQ223.122

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