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Alternative TitleCo-culture of Clostridium thermocellum and Clostridium thermosaccharolyticum for enhancing hydrogen production via thermophilic fermentation of cornstalk
Thesis Advisor刘春朝
Degree Grantor中国科学院研究生院
Degree Discipline生物化工
Keyword玉米秸秆   高温发酵   共培养   氢气   微波-碱预处理
Abstract利用廉价、可再生的木质纤维素生物质生产氢气是发展清洁能源的重要研究方向,将具有纤维降解能力的热纤梭菌与嗜热产氢菌进行共培养,为进一步提高氢气产量和底物转化效率提供了一种有效手段。本文就嗜热厌氧梭菌共培养发酵秸秆产氢过程进行了研究,并结合微波-碱预处理强化了发酵产氢过程,取得主要结果如下: 1) 对5株热纤梭菌发酵产氢过程进行了研究,实验结果表明,热纤梭菌能够很好地利用纤维素底物发酵产氢。其中,菌株7072的产氢能力最高,当以微晶纤维素为底物时,氢气产量为6.53 mmol/g-cellulose,微晶纤维素降解率可达93.78%;以秸秆为底物时,氢气产量为1.57 mmol/g-cornstalk,秸秆降解率为52.28%。 2) 筛选出嗜热解糖梭菌869与热纤梭菌7072按0.25:1比例接种作为高效产氢的共培养体系,确定了先接入热纤梭菌,后接入嗜热解糖梭菌且接种时间间隔为24 h的最佳接种策略,氢气产量达到3.04 mmol/g-cornstalk,比热纤梭菌单培养提高94.08%。产氢水平的提高与糖积累浓度和乙醇合成量的降低、乳酸的消失及挥发酸产量的增加相对应。在8 L搅拌反应器中,共培养氢气产量达到3.35 mmol/g-cornstalk,最大产氢速率为18.5 mL H2/L?h,分别比厌氧瓶中的实验数据提高9.96%和31.21%。 3) 在微波流化床中进行秸秆碱预处理,当碱用量为0.12 g-NaOH/g-cornstalk,微波处理时间为45 min,料液液固比为50:1,并且流速为60 mL/s时,秸秆中的木质素脱除率为60.31%,预处理秸秆的氢气产量达到4.71 mmol/g-cornstalk,比未处理秸秆的氢气产量提高54.8%,底物中半纤维素和纤维素的降解率分别为79.55%和71.28%。在8 L搅拌反应器中的氢气产量达到5.17 mmol/g-cornstalk,比未处理秸秆的氢气产量提高54.48%,表明微波-碱预处理能够有效提高底物转化率和氢气产量。
Other AbstractBiological hydrogen production from renewable lignocellulosic biomass attracts significant attention and becomes the key issue of current clean energy research. Clostridium thermocellum, with the highest rate of cellulose degradation, can co-culture with another thermophilic hydrogen-producing bacterium to increase hydrogen production and substrate conversion efficiency. In the current study, enhancement of hydrogen production process via thermophilic fermentation from raw cornstalk and microwave-assisted alkali pretreated cornstalk by co-culture of Clostridium thermocellum and Clostridium thermosaccharolyticum were investigated in detail. The principal results are as follows: 1) Five strains of C. thermocellum were employed for hydrogen production tests. It was shown that C. thermocellum could utilize cellulose to produce hydrogen. Among the five strains, C. thermocellum 7072 produced much more hydrogen than others. When C. thermocellum 7072 was cultured on microcrystalline cellulose, the hydrogen yield reached 6.53 mmol/g-cellulose, and the degradation of microcrystalline cellulose was 93.78%. Meanwhile, the obtained hydrogen yield of C. thermocellum 7072 was 1.57 mmol/g-cornstalk, and the degradation of cornstalk was 52.28%. 2) The co-culture of C. thermosaccharolyticum 869 and C. thermocellum 7072 at the inoculation ratio of 0.25: 1 (v/v) produced more hydrogen from cornstalk than other cultures. The strategies of inoculation in the co-culture process were optimized, and the hydrogen yield reached 3.04 mmol/g-cornstalk as the inoculation of C. thermocellum cultures was followed by C. thermosaccharolyticum inoculation after 24 h, which was 94.08% higher than that in the mono-culture, corresbonding to lower level of ethanol synthesis and disappearance of lactate, together with more VFAs formation. An 8 L stirred tank reactor system was developed for the scale-up of separate inoculation co-culture hydrogen fermentation. The hydrogen yield and maximum hydrogen production rate in the bioreactor reached 3.35 mmol/g-cornstalk and 18.5 mL H2/L?h, which were 9.96% and 31.21% higher than those in the 125 mL anaerobic bottles, respectively. 3) The alkali pretreatment of cornstalk was developed in a dynamic microwave pretreatment system, and key factors affecting the pretreatment process were optimized and evaluated for enhancing thermophilic hydrogen production by co-culture of C. thermocellum 7072 and C. thermosaccharolyticum 869. About 60.31% of lignin was effectively removed, when raw cornstalk was irradiated by microwave for 45 min with an alkali loading of 0.12 g-NaOH/g-cornstalk, where the liquid/solid ratio and flow rate were 50: 1 and 60 mL/s, respctively. The hydrogen yield reached 4.71 mmol/g-cornstalk, which was 54.8% higher than that from untreated cornstalk, and the degradations of hemicellulose and cellulose were 79.55% and 71.28%, respectively. The hydrogen fermentation process from pretreated cornstalk was also scaled up in an 8 L stirred tank reactor, and the hydrogen yield reached 5.17 mmol/g-cornstalk, which was 54.48% higher than that from raw cornstalk, together with a more rapid hydrogen production rate. It was concluded that the microwave-assisted alkali pretreatment effectively increased substrate conversion effiency and hydrogen yield in co-culture fermentation process.
Document Type学位论文
Recommended Citation
GB/T 7714
李佥. 嗜热厌氧梭菌共培养强化秸秆发酵产氢[D]. 中国科学院研究生院,2013.
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