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生物质预处理过程及酶解发酵乙醇的研究
付小果
学位类型博士
导师陈洪章
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 等离子体 秸秆 药用植物 燃料乙醇
摘要

生物质资源综合利用是全世界研究的热点。论文以典型生物质原料秸秆和药用植物(葛根、杜仲叶)为代表,比较汽爆与等离子体预处理对抗降解屏障破除、药用活性成分提取及酶解过程的影响,并解析其作用机制;在此基础上,构建秸秆和葛根乙醇及综合利用炼制模式,同时验证其可行性。论文取得的主要研究结果如下:(1) 将汽爆处理的生物质原料从秸秆拓展到药用植物:控制汽爆参数,选择性提高半纤维素降解率,降低水洗液抑制物浓度,建立玉米秸秆的选择性汽爆拆分处理工艺。研究了低强度(0.4-1.0 MPa,2-4 min)汽爆处理新鲜葛根代替30-120 min蒸煮糊化的过程,提出了淀粉质原料的汽爆糊化处理工艺。发明了空气耦合蒸汽汽爆处理杜仲叶提取绿原酸工艺,低温、快速汽爆破壁使杜仲叶疏松多孔,绿原酸的提取得率和表观提取速率常数(K)分别为未处理物料的1.62倍和5.23倍,提取平衡时间从120 min降低为15 min。而且空气蒸汽耦合的低温效应使绿原酸的物理化学结构和药用活性不受破坏。(2) 研究了常温常压介质阻挡等离子体预处理对抗降解屏障破除、药用活性成分提取及酶解过程的影响,并与汽爆处理进行比较。等离子体处理后,绿原酸提取率和玉米秸秆表皮渗透率较未处理物料分别提高14.27%和30.12%,低于汽爆处理物料绿原酸提取率和渗透率的增加率(62.49%和43.16倍);但等离子体因其独特的高能活性粒子,可完成汽爆处理不能进行的反应。等离子体周期作用木质纤维素酶解研究发现,随等离子体强度增加,纤维素酶液的酶活先提高后降低,等离子体功率75 W处理30 s的纤维素酶液的酶活达到最高,较未处理纤维素酶提高了14.35%。在纤维素酶用量20 FPU/g底物,酶解72 h时,以1 h为周期等离子体作用于酶解体系,酶解率和酶解反应速率常数较未等离子体处理酶液分别提高了52.26%和45.71%,而达到相同酶解率所需的纤维素酶用量降低了31.52%。(3) 等离子体处理的效率与等离子体环境以及物料的特性密切相关。研究了放电参数(功率、时间和气体流速等)对半纤维素和纤维素降解制糖效率的影响,确定了放电参数:放电功率100 W,H2O流量0.1 L/min,N2流量为0.5 L/min。在此条件下等离子体处理低聚糖溶液30 min,木糖得率为44.52%,而等离子体处理微晶纤维素120 min,葡萄糖得率达到45.89%。球磨处理是降低玉米秸秆颗粒度,提高等离子体反应效率的有效方式之一,球磨2 h后等离子体处理20 min物料,玉米秸秆葡聚糖和木聚糖的转化率较未处理原料分别提高了41.04%和65.94%。等离子体反应机制初步解析表明,等离子体离解体系中水分子产生酸性物质,富集形成酸性质子鞘层,破坏生物质结晶区,并使糖苷键断裂。(4) 研究了汽爆预处理参数、底物浓度、加酶量以及预酶解时间对玉米秸秆酶解发酵乙醇的影响,建立了汽爆玉米秸秆固相预酶解-同步糖化全糖发酵乙醇工艺。年产2万吨秸秆乙醇产业化运行时乙醇浓度达到4.15%,为理论乙醇产率的72.3%,验证了该工艺的工业化可行性。(5) 研究了汽爆葛根固态同步糖化发酵乙醇以及发酵剩余物提取葛根黄酮的可行性,提出了葛根能源化清洁炼制模式。采用此炼制模式,乙醇和黄酮得率分别为9.20 g/100g鲜葛根和1.87 g/100g葛根,淀粉利用率达到95.0%,实现了葛根组分分级转化、清洁利用,为非粮淀粉质原料生产燃料乙醇奠定了技术基础。

其他摘要

Biomass utilization has attracted great attention in the world. In this paper, the objective feedstocks were corn stover and medicinal plants. According to the characteristics of feedstocks and the desired productions, the specific pretreatment process was established with steam explosion and low-temperature plasma technology. The effects of pretreatment process on the recalcitrance disruption, extraction of the active ingredient and efficiency of enzymatic hydrolysis were evaluated, also its mechanism was discussed. The utilization pattern of starch-rich medicinal plants to produce ethanol was achieved by steam explosion, expanding the feedstock for bio-ethanol production. The feasibility of the large-scale pre-hydrolysis and simultaneous saccharification and fermentation ethanol was approved, which may provide the guidance for the commercial bioethanol production.The main results were obtained as follows:(1) The biomass of steam explosion pretreatment were expanded from corn stover to medicinal plants. Firstly, through controlling the parameters, the hemicellulose degradation rate was selectively improved, and the inhibitor concentration within the hydrolysate was reduced. Therefore, the selective-fractionation technology of corn stover using steam explosion pretreatment has been established. Secondly, the gelatinization process of the rich-starch feedstock with 30-120 min was replaced by unpolluted steam explosion pretreatment (0.4-1.0 MPa, 2-4 min), thereby the gelatinization process of starch-feedstock with steam explosion was established. Lastly, a novel air-steam explosion with low temperature was developed to treat Eucommia ulmoides leaves, in order to achieve the desirable extraction yield of thermosensitive chlorogenic acid. After pretreatment for 120 s, the yield and extraction rate of chlorogenic acid from air-steam exploded sample were 2.83% and 0.246 min-1, respectively, which were 62.49% and 423.0% higher than those of raw sample. Additionally, the equilibrium time of chlorogenic acid extraction decreased from 120 min to 15 min. The fibrous networks and the cell walls of the leaves were destroyed by air-steam explosion pretreatment, which improved the solute-solvent accessibility and the internal mass transfer during extraction process. (2) The atmospheric-pressure dielectric barrier discharges plasma pretreatment (ADBDPP) was introduced. The effects of pretreatment process on the recalcitrance disruption, extraction of the active ingredient and the process of enzymatic hydrolysis were evaluated, and compared with steam explosion pretreatment. After ADBDPP, the yield of chlorogenic acid and the permeability of corn stover rind were increased by 14.27% and 30.12% compared with that of the untreated material, respectively, but the yield and permeability from steam exploded feedstock were increased by 62.49% and 431.60%. However, owing to the special high-energy particle, ADBDPP was able to react, which would not be done by steam explosion treatment. Plasma was employed in the enzymatic hydrolysis and the correlation of plasma, cellulase activity and enzymatic hydrolysis of corn stover was evaluated. Results showed that the cellulase activity was increased, and then decreased with the increase of plasma intensity. The highest cellulase activity was achieved when the cellulase was treated with plasma at 75 W for 30 s, under which the cellulase activity was increased by 14.35% than that of untreated sample. The enzymatic hydrolysis yield and velocity constant with the plasmas duty cycle of 1 h were increased by 52.26% and 45.71%, respectively, whereas the enzyme loading was decreased by 31.52% to achieve the same hydrolysis yield.(3)The efficiency of ADBDPP was closely related to the plasma parameters and the characteristics of feedstock. The effects of ADBDPP parameters (plasma power, plasma time and gas flow rate) on xylose and glucose conversion rate were analyzed, then the optimized plasma parameters were attained, which was plasma power of 100 W, N2 of 0.5 L/min and H2O of 0.1 L/min. Under the optimized condition, the xylose and glucose conversion rate from hemicellulose oligosaccharides and microcrystalline cellulose were increased by 44.52% and 45.89%, respectively. The particle size of corn stover was reduced using ball milling treatment, which resulting in improved the efficiency of ADBDPP. After the ball milling treatment of 2 h and ADBDPP of 20 min, the glucan and xylan conversion rate were increased by 41.04% and 65.94% than that of untreated corn stover. The reactive particle was gained in the process of ADBDPP, which resulted in the acid reaction with biomass. Furthermore, the crystal structure and the hydrogen bonds were disrupted to break glycoside.(4) The effects of solid loading, enzyme loading, pre-hydrolysis time and steam explosion parameters on the efficiency of enzymatic hydrolysis and simultaneous saccharification and ethanol fermentation were studied, and the optimized parameters were attained. Based on these paramaters, the pre-hydrolysis and simultaneous saccharification and ethanol fermentation (PHSSEF) for steam exploded corn stover was established. The yield of ethanol reached 4.15%, which corresponded to72.3% theoretical yield of ethanol in the large-scale project. Therefore, the feasibility of PHSSEF in industrialization was approved.(5) The production of ethanol and isoflavones from steam-exploded Kudzu by solid state fermentation was established. The yield of ethanol and isoflavones was 9.20 g/100g fresh Kudzu and 1.87 g/100g Kudzu, respectively, and the utilization rate of starch was 95.0%. Therefore, the process was clean and energy-saving, which provided a new way of starch-rich medical plants utilization, and expanded the feedstock for production ethanol. 

语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/22890
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付小果. 生物质预处理过程及酶解发酵乙醇的研究[D]. 北京. 中国科学院研究生院,2016.
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