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汽爆秸秆同步糖化发酵丁醇过程的研究
李静雯
学位类型硕士
导师陈洪章 ; 王岚
2016-07
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业生物化工
关键词汽爆 丁醇发酵 直投式发酵剂 发酵抑制物 周期蠕动
摘要

经济可行的丁醇发酵技术是近年来国内外生物质能源领域研究的热点和难点。目前木质纤维素发酵丁醇过程中的一些关键技术尚未突破,制约了丁醇作为液体燃料的经济竞争力。论文围绕丙酮丁醇梭菌直投式发酵剂的开发,发酵抑制物的脱毒和木质纤维素同步糖化发酵丁醇体系的强化等方面进行了深入研究,为经济可行的丁醇发酵技术的开发及其产业化奠定基础。 (1)活性菌体的干燥是丙酮丁醇梭菌直投式发酵剂开发中的关键环节。针对丙酮丁醇梭菌在传统热力干燥过程中存活率和发酵活力低的问题,考察了该菌的干燥特性,比较了不同干燥方法对菌活力的影响,发现高温、氧化和结合水的迁移是热力干燥过程中菌体质量退化的主要原因。开发了吸附载体—氮气热风二段干燥工艺,以10.0 g/L海藻糖、0.01 g/L生物素、2.0 g/L维生素C为保护剂,麦麸为吸附载体,将丙酮丁醇梭菌干燥至10%含水量,存活率和发酵活力分别达到75.7%和58.1%,是普通氮气热风干燥的2.3倍。此工艺适合于严格厌氧细菌的大规模干燥过程,有干燥效率高、能耗低的优点。 (2)为降低汽爆秸秆降解物对发酵的抑制作用,考察了不同汽爆条件下各类抑制物的生成规律,发现弱酸类物质和可溶性木质素是汽爆秸秆酶解液中影响丁醇发酵的关键抑制物。证实了可溶性木质素中非酚类物质也具有抑制发酵的作用。开发了减压蒸馏—漆酶-介体处理的两步脱毒工艺。利用12%的汽爆秸秆酶解液发酵丁醇,总溶剂产量达12.6 g/L,产率为0.13 g/(L·h),得率为0.21 g/g,可发酵性糖利用率达96%以上。 (3)为提高汽爆秸秆同步糖化发酵丁醇过程的传递效率,提高丁醇产率,应用了一种新型的周期蠕动强化方法。在17.5%汽爆秸秆同步糖化发酵体系中,总溶剂产量达17.1 g/L,产率达0.20 g/(L·h),远高于静置反应的15.2 g/L和0.14 g/(L·h)。周期蠕动下,初始12 h的单糖转化率为4.67 g/(L·h),比静置提高了49.7%。丁醇发酵周期由108 h缩短至84 h。周期蠕动的最优条件是作用于丁醇同步糖化发酵产酸期(0-48 h),以低频(6 h-1)强化。说明周期蠕动是一个提高高固体系下同步糖化发酵丁醇产率的有效方法。 

其他摘要

Economically feasible butanol fermentation technology is the focus and difficulty in biomass energy development in recent years. So far, some key techniques of butanol fermentation from lignocellulose have not been solved, restricting the economic competitiveness of biobutanol. This paper intensively focuses on the development of the direct vat set starter culture of Clostridium acetobutylicum, the detoxification of fermentation inhibitors and the intensification of butanol production by the simultaneous saccharification and fermentation (SSF) from lignocellulose. This study provides an economically feasible foundation for the development and industrialization of butanol fermentation. (1) The dehydration is the key process of the development of the direct vat set starter culture of C. acetobutylicum. The viability and activity of the bacteria are low for traditional thermal drying techniques. To solve these problems, the drying properties of C. acetobutylicum were determined and the effect of different drying methods on the activity of bacteria was compared. Results showed high temperature, oxidation and water transfer were the main causes of bacteria degradation in a thermal drying process. A novel two-stage drying process combined the absorption with the hot-nitrogen drying was developed with the combinations of protectants of 10.0 g/l-trehalose, 0.01 g/l-biotin and 2.0 g/l-vitamin c, and bran as the desiccant. The viability and activity of C. acetobutylicum were 75.7% and 58.1% with 10% water content, respectively, which were 2.3 times more than the normal nitrogen drying process. This novel process was suitable for the dehydration of the strict anaerobic bacteria, which had the advantages of high efficiency and low energy consumption. (2) To reduce the degradation inhibition from steam explosion process to butanol fermentation, the formation of inhibitors were investigated under different conditions of steam explosion. Results showed that weak acids and soluble lignin were the key inhibitors to butanol fermentation of the hydrolysate of steam-exploded corn straw. Results confirmed that non-phenolic compounds of soluble lignin showed an obvious inhibition on butanol fermentation. A novel two-step detoxification method of vacuum distillation and laccase-mediator was developed. The concentration of acetone-butanol-ethanol (ABE) at a solids content of 12% (w/w) was up to 12.6 g/L, a productivity of 0.13 g/(L·h), a yield of 0.21 g/g and the utilization of fermentable sugar was over 96%. (3) Periodic peristalsis, a novel intensification method, was applied to improve the efficiency of mass transfer and ABE production by simultaneous saccharification and fermentation (SFF) of steam-exploded corn straw. The ABE concentration and the ABE productivity of SSF at a solids content of 17.5% (w/w) with periodic peristalsis were 17.1 g/L and 0.20 g/(L·h), respectively, which were higher than those obtained under static conditions (15.2 g/L and 0.14 g/(L·h)). The initial sugar conversion rate over the first 12 h with periodic peristalsis was 4.67 g/(L·h), an increase of 49.7% compared with the static conditions. With periodic peristalsis, the period of batch fermentation was shortened from 108 h to 84 h. The optimal operating regime was a low frequency (6 h-1) of periodic peristalsis in the acid-production phase (0-48 h) of SSF. Therefore, periodic peristalsis should be an effective intensification method to increase the productivity of ABE fermentation at high solids content. 

语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/22862
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李静雯. 汽爆秸秆同步糖化发酵丁醇过程的研究[D]. 北京. 中国科学院研究生院,2016.
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