乳酸生产中的微生物代谢工程

从代谢工程的角度综述了同型及异型乳酸发酵的代谢途径、乳酸菌代谢模型、乳酸脱氢酶在乳酸生产方面的应用、米根霉发酵生产乳酸的代谢工程和基因工程阻断乙醇代谢途径改造乳酸的生产过程等方面的研究进展,讨论了生物信息学及环境胁迫对乳酸代谢的影响,展望了乳酸的微生物代谢工程的发展趋势.     

工艺因子对于MFC中能量分配的协同效应分析

微生物燃料电池（MFC）以产电和代谢的方式利用系统能量实现有机物降解。针对运行过程中能量的不同分配需求,以pH、有机负荷、溶解氧、电导率和外电阻为工艺因子,采用正交实验方法优选最佳工艺条件,从而实现MFC能量流调控的目的。研究表明：在实验工况下,最高产电能量转化效率和生物代谢能量利用效率分别为8.74%和66.03%,负荷和外电阻对产电能量转化效率有显著影响,负荷和pH对能量利用效率有显著影响,系统能量主要以生物代谢方式被利用。由此可见,在同等负荷条件下,若将MFC作为电转化单元时应主要控制其外电阻,若需提高MFC的有机物降解能力时pH则是首要控制因素。     

工艺因子对于MFC中能量分配的协同效应分析

微生物燃料电池(MFC)以产电和代谢的方式利用系统能量实现有机物降解。针对运行过程中能量的不同分配需求,以p H、有机负荷、溶解氧、电导率和外电阻为工艺因子,采用正交实验方法优选最佳工艺条件,从而实现MFC能量流调控的目的。研究表明:在实验工况下,最高产电能量转化效率和生物代谢能量利用效率分别为8.74%和66.03%,负荷和外电阻对产电能量转化效率有显著影响,负荷和p H对能量利用效率有显著影响,系统能量主要以生物代谢方式被利用。由此可见,在同等负荷条件下,若将MFC作为电转化单元时应主要控制其外电阻,若需提高MFC的有机物降解能力时p H则是首要控制因素。     

以加热预处理污泥上清液为底物的微生物燃料电池基础特性

以单室空气阴极微生物燃料电池(MFC)为反应器,考察了以加热预处理污泥上清液为底物的MFC产电情况. 结果表明,污泥90℃下加热3 h时MFC输出功率最高(44.4 mW/m2),是未加热的105倍. 在此预处理条件下,污泥上清液中所含有机物成分最有利于阳极微生物的代谢产电. 加热后的污泥再次加热作为MFC底物产电,输出功率只有5.8 mW/m2. 加热预处理可提高以污泥上清液为底物的MFC的输出功率,且易与现有工艺结合,更接近实际应用.     

Biolog鉴定产氢发酵细菌及其产氢能力的研究

采用厌氧培养技术,从厌氧活性污泥中分离得到一株产氢发酵细菌。利用B iolog自动菌种鉴定仪对该产氢发酵细菌作了鉴定分析,确定了其在细菌学上的分类地位,新分离菌株C lostridium papyrosolvens为生物制氢分离鉴定纯产氢菌种提供了指导,该菌株为专性厌氧杆菌,蔗糖发酵液体末端主要产物为乙醇、乙酸,气相产物为H2和CO2,代谢特征为乙醇型发酵,在pH 6.0和36℃条件下最大产氢量为72 mL H2/g蔗糖。     

利用糖蜜废水产乳酸细菌的分离与鉴定

为获得可利用糖蜜废水产生乳酸的细菌,采用厌氧Hungate培养技术,从糖蜜废水处理生物反应器中获得活性污泥,分离到一株乳酸菌MD-9。对该株细菌进行了形态学特征、生理生化指标、16S rRNA基因序列分析等研究。结果表明与最相近的种属Lactobillus fermnetus的16S rRNA基因序列同源性为99.6%。该株细菌为兼性厌氧杆菌,葡萄糖代谢特征为专性异型发酵,可以利用糖蜜废水产生乳酸。     

微生物燃料电池处理丙酮和氨氮废水及同步产电性能研究

本研究利用阴离子交换膜作为分隔膜构建了生物阴极微生物燃料电池（Microbial fuel cell, MFC），通过硝化反硝化过程去除氨氮、降解丙酮同时产电。实验探究了不同丙酮浓度（50 mg/L、100 mg/L、300 mg/L、500 mg/L、700 mg/L）对MFC产电及氨氮（200 mg/L）的去除效果。结果表明，在选定的丙酮浓度范围内，丙酮的去除率均高达96%以上；当丙酮浓度高于300 mg/L时，氨氮的去除开始受到抑制，氨氮最高去除率为73.7%，且丙酮浓度为300 mg/L时，对应的MFC的产电性能最佳，最高输出功率密度可达49.7 mW/m2。高通量测序技术分析了阳极及阴极微生物群落结构，从门级分类上看，阳极中的优势微生物群落主要为变形菌，拟杆菌门及厚壁菌门；阴极上的优势微生物群落为拟杆菌门、放线菌门、变形菌门及酸杆菌门。从属级分类上看，阳极主要的优势菌种为Comamonas, Acetoanaerobium，Stenotrophomonas。阴极主要的优势菌种为Rhodococcus，Aridibacter, Thauera，Ignavibacterium。     

微生物燃料电池处理含铬废水并同步产电

以葡萄糖为阳极燃料、含铬废水为阴极液,碳毡为阳极、石墨板为阴极构建了双室微生物燃料电池,考察了阳极条件(底物浓度)及阴极条件(pH、初始六价铬浓度)对含铬废水的降解及MFC的产电性能的影响.结果表明低阴极液pH和高初始Cr(Ⅵ)浓度能改善MFC产电性能.当pH=2、初始六价铬浓度为177 mg/L、反应时间为10 h时,最大输出功率为108 mW/m~2,六价铬去除率为92.8%.阳极底物浓度对微生物燃料电池的性能也有影响.在微生物燃料电池中,阴极极化较小,表明该燃料电池有稳定的性能,微生物燃料电池对含铬废水的处理有应用潜力并能同步产电.     

运行因素对猪场废水微生物燃料电池产电性能的影响

以猪场废水为基底构建双室微生物燃料电池,分别研究温度、pH和阳极液搅拌对微生物燃料电池(MFC)产电性能和废水净化效果的影响。结果表明,在一定范围内,温度的提升有助于增强微生物的电化学活性,微碱性条件下MFC的输出电压和功率密度更佳,阳极室的搅拌有利于提升电池产电和除污性能。实验确定了基于猪场废水处理微生物燃料电池的较优运行因素,为推动微生物燃料电池在污水处理方面的实际应用提供参考。     

双极室微生物燃料电池处理不同阳极底物废水的产电研究

为了研究微生物燃料电池(MFC)在不同阳极底物废水条件下的产电效率和废水处理效果。分别以啤酒废水、糖蜜废水和啤酒-糖蜜混合废水作为阳极基质,含银电镀废水作为阴极电子受体,构建了双极室微生物燃料电池。结果表明,3组以糖蜜废水作为阳极基质的MFC产电量和COD去除率最高,啤酒废水次之,啤酒-糖蜜混合废水最低。糖蜜废水作为阳极基质的MFC最高电压和功率密度可达356 m V和36.21 m W/m~2,第3周期时COD去除率达到最高的69.29%,实验结束时阴极Ag~+的质量浓度最低至304 mg/L。不同阳极基质对MFC产电效率和废水处理效果有影响。     

厌氧活性污泥产电特性及产电过程微生物群落变化

以厌氧活性污泥为接种液构建微生物燃料电池(MFC),检测了运行第1周期前后电池的理化性质及菌群变化情况。结果表明,MFC启动后产电性能良好,外接1000 Ω电阻时输出电压可达0.62 V,功率密度达1247 mW/m2,内阻为143 Ω, 化学需氧量(COD)去除率达63.6%;高通量测序结果显示,MFC菌群与原始接种厌氧活性污泥菌群相比变化较明显,菌群多样性指数降低,优势菌门硬壁菌门(Firmicutes)和变形菌门(Proteobacteria)为产电菌群常见门,与MFC产电能力直接相关的克雷伯氏菌属(Klebsiella)富集并成为优势菌属,相对丰度达16.73%。     

Synthetic Saccharomyces cerevisiae‐Shewanella oneidensis consortium enables glucose‐fed high‐performance microbial fuel cell

Microbial fuel cells (MFCs) were green and sustainable bio‐electrochemical reactors for simultaneous wastewater treatment and electricity harvest from organic wastes. However, exoelectrogens, such as Shewanella and Geobacter being widely studied in MFCs, could only use a limited spectrum of carbon sources. To expand the carbon source range being used in MFCs, we herein rationally designed a glucose‐fed fungus‐bacteria microbial consortium including a fermenter (Saccharomyces cerevisiae) in which the ethanol pathway was knocked out and the lactic acid biosynthesis pathway from Bovin was introduced into S. cerevisiae, and an exoelectrogen (Shewanella oneidensis MR‐1). We optimized the co‐culturing conditions of the microbial consortium to achieve an optimal coordination between carbon source metabolism of the fermenter and extracellular electron transfer of the exoelectrogen, such that lactate, the metabolic product of glucose by the recombinant S. cerevisiae, was continuously supplied to S. oneidensis in a constant level until glucose exhaustion. This metabolic coordination between the fermenter and the exoelectrogen enabled bioelectricity production in a glucose‐fed MFC. Furthermore, a porin protein encoded by oprF gene from Pseudomonas aeruginosa was incorporated into the outer membrane of S. oneidensis to enhance membrane permeability and its hydrophobicity, which in turn facilitated its biofilm formation and power generation. The glucose‐fed MFC inoculated with the recombinant S. cerevisiae‐recombinant S. oneidensis generated a maximum power density of 123.4 mW/m², significantly higher than that of recombinant S. cerevisiae‐wild‐type S. oneidensis (71.5 mW/m²). Our design strategy of synthetic microbial consortia was highly scalable to empower the possibility of a wide range of carbon sources being used in MFCs, e.g., xylose, cellulosic biomass, and recalcitrant wastes. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1830–1838, 2017     

Production of L‐lactic acid with very high gravity distillery wastewater from ethanol fermentation by a newly isolated Enterococcus hawaiiensis

BACKGROUND: A great amount of wastewater with high contents of chemical oxygen demand (COD) are produced by ethanol production. It would be useful to utilize distillery wastewater to produce L‐lactic acid, which could be a high additional value byproduct of ethanol production. The fermentation process of L‐lactic acid production by a newly isolated Enterococcus hawaiiensis CICIM‐CU B0114 is reported for the first time. RESULTS: The strain produced 56 g L^?1 of L‐lactic acid after cultivation for 48 h in optimized medium consisting of (g L^?1) 80 glucose, 10 peptone, 10 yeast extract, 1.5 Na₂HPO₄ and 0.2 MgSO₄. E. hawaiiensis CICIM‐CU B0114 was isolated and purified by subculture for growing and producing L‐lactic acid in distillery wastewater of very high gravity (VHG) from ethanol fermentation. L‐lactic acid fermentation was further studied with distillery wastewater substrate in 7 L and 15 L fermentors. The results showed that L‐lactic acid concentrations of 52 g L^?1 and 68 g L^?1 was achieved in 7 L and 15 L fermentors with the initial sugar concentrations of 67 g L^?1 and 87 g L^?1, respectively. CONCLUSION: The production of L‐lactic acid by the newly isolated E. hawaiiensis CICIM‐CU B0114 was carried out and the fermentation medium was optimized by orthogonal experimental design. This new strain holds the promise of L‐lactic acid production utilizing distillery wastewater from VHG ethanol fermentation. Copyright © 2010 Society of Chemical Industry     

米根霉发酵生产L(+)-乳酸研究进展

米根霉是生产绿色平台生物化学品L(+) 乳酸的理想菌种 ,目前集中在发酵工艺的优化、新型生物反应器的设计以及细胞固定化等方面的研究 ,通过控制米根霉菌体形态使之自聚集成为一定大小的球体进行乳酸发酵 ,操作简便、费用低。建议今后从应用代谢工程技术定向选育米根霉L(+) 乳酸高产菌 ,改进发酵设备、改良提取工艺 ,合理控制乳酸产品的构型等几个方面着手进行进一步研究 ,从而降低乳酸生产原料的成本 ,扩大L(+) 乳酸的应用领域。     

从生物量生产丙烯酸的研究和开发进展

1 INTRODUCTION Energy resources are divided into two categories: renewable and non-renewable. The fossil energy re- sources, such as petroleum, coal, natural gas and nu- clear energy, are non-renewable, whereas solar energy, hydraulic energy, wind power as well as biomass, etc., are renewable. Nowadays, worldwide efforts to reduce atmospheric CO2 emissions and to overcome the shortage and sharp price rise of fossil energy resources, especially petroleum, simultaneously trigger research on…     

发酵液中乳酸的分离提取研究进展

乳酸是合成聚乳酸的原料,生物法制备乳酸是目前工业上生产乳酸的主要方法。但乳酸发酵液成分复杂,后续的分离提纯过程成了制约乳酸生产的技术瓶颈和难点,也决定着乳酸的品质与收率。本文对乳酸发酵液的主要的分离提取工艺进行了介绍,包括结晶分离技术、酯化水解法、萃取法、分子蒸馏法、膜分离法、吸附法及与发酵耦合的原位分离技术。并提出单一的分离技术很难有效提取乳酸,需将多种技术集成、改良提纯工艺路线。其中,将各种新型高效的集成技术与发酵过程的有机结合,实现连续或半连续的发酵过程,可提高乳酸产率和产品质量,有望形成高效率、高品质、低污染、低能耗、可工业化的乳酸提纯工艺路线。     

Use of sweet sorghum juice for lactic acid fermentation: preliminary steps in a process optimization

BACKGROUND: Lactic acid has many applications in the chemical industries and it can be produced economically by microorganisms using biomass raw materials of different origins. Sweet sorghum juice is a high sugar content raw material with potential for lactic acid production because after hydrolysis of its sucrose content the remaining glucose and fructose can supply the carbon demand of most lactic acid bacteria. However, satisfying the nitrogen and B‐vitamin needs of the bacteria by supplementation with yeast extract and/or other alternative nitrogen‐containing supplements can make the process too expensive. RESULTS: Using a statistical optimization process much of the yeast extract can be replaced by a cheaper alternative nitrogen source, namely wheat gluten. This resulted in a fermentation with 99% lactic acid yield and 3.04 g L^?1 h^?1 volumetric productivity. CONCLUSION: Using response surface methodology (RSM) media optimization was performed for lactic acid fermentation with an industrially acceptable result, reducing the costs of raw materials by half, replacing yeast extract by an alternative nitrogen source and applying yeast extract only as a source of micro‐elements (vitamins, salts, etc.) Copyright © 2010 Society of Chemical Industry     

Improved energy recovery from dark fermented cane molasses using microbial fuel cells

A major limitation associated with fermentative hydrogen production is the low substrate conversion efficiency. This limitation can be overcome by integrating the process with a microbial fuel cell (MFC) which converts the residual energy of the substrate to electricity. Studies were carried out to check the feasibility of this integration. Biohydrogen was produced from the fermentation of cane molasses in both batch and continuous modes. A maximum yield of about 8.23 mol H₂/kg COD_removed was observed in the batch process compared to 11.6 mol H₂/kg COD_removed in the continuous process. The spent fermentation media was then used as a substrate in an MFC for electricity generation. The MFC parameters such as the initial anolyte pH, the substrate concentration and the effect of pre-treatment were studied and optimized to maximize coulombic efficiency. Reductions in COD and total carbohydrates were about 85% and 88% respectively. A power output of 3.02 W/m³ was obtained with an anolyte pH of 7.5 using alkali pre-treated spent media. The results show that integrating a MFC with dark fermentation is a promising way to utilize the substrate energy.     

生物质转化制备乳酸及其酯类物质研究进展

乳酸是重要的精细化工中间体,在食品、医药、日化及可降解材料等领域具有重要的应用.利用农林废弃物为原料转化制备乳酸,不仅能够充分利用生物质资源,更能缓解乳酸供需矛盾,对推动碳减排及绿色发展具有重要意义.分别从微生物发酵法和化学催化法对生物质转化制备乳酸(酯)的最新研究进展进行了综述,并对当前阶段制约乳酸生产的各方面因素进行了分析总结,最后全面比较了这两种方法的优缺点,展望了生物质转化制备乳酸潜在研究方向、存在的机遇和面临的挑战.