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甜高粱秸秆高温发酵联产氢气和挥发性脂肪酸
MD SAIFUL ISLAM
Thesis Advisor刘春朝
2018-06
Degree Grantor中国科学院大学
Degree Name博士
Degree Discipline生物化工
Keyword氢气,有机酸,酸处理,碱结合酶处理
Abstract

面对当今世界对可再生能源日益增长的需求,氢气作为一种环保、高能可再生能源,可保障未来的能源安全。木质纤维素生物质可转化并产生能源和化学品,替代化石燃料满足能源需求,同时减少二氧化碳的大气排放,是一类环境友好型的可再生资源。 本论文主要关注甜高粱秸秆的厌氧生物发酵产氢气和挥发性脂肪酸。由于在微生物发酵过程中,甜高粱秸秆所含的纤维素和半纤维等结构性多糖难以被有效利用,如何提高结构性多糖的利用度和发酵产物的产量,成为本论文研究重点。 共培养Clostridium thermocellum和Clostridium thermosaccharolyticum发酵甜高粱秸秆,当底物浓度为5 g/L,接种C. thermocellum 培养24h之后,以1:1比例接种C. thermosaccharolyticum可以获得最大的氢气和挥发性脂肪酸产量,氢气产量为5.1 mmol/g-substrate,乙酸为1.27 g/L,丁酸为1.05 g/L。相比于单菌培养氢气、乙酸和丁酸的产量分别提高了55 %、9 %、10 %。 通过C. thermosaccharolyticum两步发酵结合稀酸处理第一步发酵残渣的新工艺,进一步提高了氢气和挥发性脂肪酸的产量。当底物浓度为10 g/L,在120°C条件下,采用1.5 %的硫酸处理第一步发酵残渣可获得最大的氢气和挥发性脂肪酸产量,总氢气、乙酸和丁酸的最高产量分别为5.77 mmol/g-substrate,2.17 g/L和2.07 g/L。相比一步发酵法提高了76 %的氢气产量,84 %的乙酸产量和113 %的丁酸产量。 通过C. thermosaccharolyticum两步发酵结合碱和酶处理第一步发酵残渣的工艺,最大限度的提高了甜高粱秸秆共产氢气和挥发性脂肪酸量。当底物浓度为10 g/L,在120°C条件下,采用2 %的NaOH处理第一步发酵残渣1h,同时结合32 FPU/g-substrate的纤维素酶消化,可获得最大的氢气和挥发性脂肪酸产量。氢气、乙酸和丁酸的最高产量分别为6.37 mmol/g-substrate,2.33 g/L和2.36 g/L,分别比一步发酵法提高了95 %的氢气产量,97 %的乙酸产量和143 %的丁酸产量。通过微生物共培养发酵结合酸、碱和酶法处理木质纤维素发酵产物,进行氢气和有机酸的共生产,可获得更多和更高的氢气产量和有机酸产量,为甜高粱的生物炼制提供了一条有前景的路径。;Hydrogen is one of the most important energy sources in future considering the energy security, increasing the demand of renewable energy and its environmental and unique high energy properties. Renewable resources, lignocellulosic biomass for fuel and chemicals production are environment-friendly due to the less emission of carbon dioxide to the atmosphere and to replace the fossil source to meet the demand. Among the biological way, this thesis focuses anaerobic fermentation for hydrogen and volatile fatty acid (VFA) production from high soluble sugar containing lignocelluloses, sweet sorghum stalk. The structural carbohydrate (cellulose and hemicellulose) is still under-utilized in the process of microbial fermentation and need to further studies to improve the production performance and being more compatible. In order to achieve the aims, potential of hydrogen and VFA coproduction was investigated from sweet sorghum stalk using Clostridium thermocellum and Clostridium thermosaccharolyticum as production microbes. The optimum conditions for the highest yield of products found as 1:1 inoculation ratio of both strains, 24 h of time gap between C. thermosaccharolyticum followed by C. thermocellum after the first inoculation and 5 g/L of substrate concentration. The maximum yield of products was observed as hydrogen (5.1 mmol/g-substrate), acetic acid (1.27 g/L) and butyric acid (1.05 g/L) at optimum conditions. Experimental data showed that co-culture increased 55 % hydrogen, 9 % acetic acid and 10 % of butyric acid production from single-culture. Improved hydrogen and VFA coproduction was studied from two step fermentation with dilute acid treatments of the residual slurry after 1st step using C. thermosaccharolyticum strain in both step. The optimum severity conditions for the highest yield of products found from the treatment acid concentration of 1.5 % (w/v) at 120 °C for 10 g/L of substrate concentration. Experimental data showed that two-steps fermentation increased 76 % hydrogen, 84 % acetic acid and 113 % of butyric acid production from single step. Maximum yields of hydrogen, acetic acid and butyric acid were 5.77 mmol/g-substrate, 2.17 g/L and 2.07 g/L respectively. Efficient co-production of hydrogen and VFA from sweet sorghum stalk was developed successfully in two-steps dark fermentation process involving alkali and enzyme treatment of the residual slurry after 1st step. The whole slurry was used without washing after alkali treatment. The optimum severity of treatment for highest yield of products was 2 % (w/v) of alkali at 120 °C along with enzyme loading for 10 g/L of substrate. The two-step fermentation using C. thermosaccharolyticum increased production by 95 % of hydrogen, 97 % of acetic acid and 143 % of butyric acid yields higher than those obtained in single step fermentation. Highest yields of hydrogen, acetic acid and butyric acid were 6.37 mmol/g-substrate, 2.33 g/L and 2.36 g/L respectively. Together these results of hydrogen and volatile fatty acid coproduction provide a promising approach and more value to the process of sweet sorghum biorefinery. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/26937
Collection中国科学院过程工程研究所
Recommended Citation
GB/T 7714
MD SAIFUL ISLAM. 甜高粱秸秆高温发酵联产氢气和挥发性脂肪酸[D]. 中国科学院大学,2018.
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