固定化运动发酵单胞菌乙醇发酵研究

以运动发酵单胞菌(zymomonas mobilis 10225)为菌种。以葡萄糖为底物进行乙醇发酵。对不同底物浓度[5％，7．5％。10％(W／V)]、不同温度(25℃,30℃，35℃)条件下，游离细胞和固定化细胞乙醇发酵的特性进行研究。实验结果表明。葡萄糖浓度为5％。25℃时可达到最大的乙醇产率0．50g乙醇／g葡萄糖。以海藻酸钙为包埋介质，对Zymomonas mobilis进行固定化。在10％葡萄糖培养基中多批次半连续发酵，可在8h内使乙醇产率系数达到0．50。短的发酵周期和高的乙醇产率为后续的葡萄糖和木糖两步乙醇发酵提供理想的实验数据。     

海带发酵产甲烷的初步研究

通过大型海藻发酵生产甲烷,可以为清洁能源开发提供新的途径。试验以海带为原料,研究其发酵产气过程及甲烷的产量,并对发酵条件进行了优化。首先,利用单因素试验研究盐度、温度、起始pH对甲烷气体产量的影响;在此基础上,应用Box-Behnken中心组合设计建立数学模型,进行三因素三水平响应面分析。优化后的发酵条件:盐度6.58,温度28.92℃,起始pH 7.07。采用优化后发酵条件进行海带发酵,60 d总产气量达到6 310 ml,与优化前产气量(5 378 ml)相比提高了17.3%。     

秸秆降解菌株的筛选及其发酵生产乙醇的研究

用滤纸赫奇逊固体培养基和纤维素固体培养基初筛,再以滤纸无机盐培养基和以羧甲基纤维素为唯一碳源的刚果红培养基进行复筛的方法,确定出10株降解效果较好的菌,通过对其纤维素酶相关性质及酶活力进行测定,综合比较降解能力,最终获得6株降解活性较强的菌,其酸性纤维素酶活较强,最优产酶时间为6d,最后采取了非等温同时糖化发酵法(Nonisothermal Simultaneous Saccharification and Fermentation,NSSF)和同步糖化发酵法(Simulta-neous Saccharification and Fermentation,SSF)进行乙醇发酵,结果表明NSSF的乙醇产率大于SSF.     

乙醇型发酵与丁酸型发酵产氢机理及能力分析

氢气是一种新型清洁能源，方便快捷的制氢方法正日益受到重视，产氢－产酸发酵过程中氢气产生的主要途径为乙醇型发酵过程和丁酸型发酵过程，在对这两种发酵类型产氢机理及能力的理论研究及对比试验中，发现乙醇型发酵途径发酵产氢能力要优于丁酸型发酵过程（平均为25％－40％），并且该文将pH值和氧化还原电位（ORP）作为综合环境因子考察，通过与发酵过程产氢量指标相配合分析，认为乙醇型发酵过程是一种较佳的有机物生物发酵制氢途径。     

生物质合成气发酵生产乙醇的工艺分析

介绍了生物质合成气发酵制备乙醇的工艺过程。采用Aspen plus软件对工艺过程建立模型,模拟计算乙醇的产量。针对影响乙醇产量的主要参数进行了灵敏度分析,结果表明:气化过程中氧气与干生物质质量比对乙醇产量影响显著,且比值为0.4时,乙醇产量最大;而气化过程中过多蒸汽的加入会降低乙醇产量;发酵过程中CO和H2转化率的提高有利于乙醇产量的增加。     

酿酒酵母代谢有机酸对乙醇发酵的影响

发酵过程中酵母代谢产生的有机酸会影响发酵效率。以葡萄糖为底物,在自动发酵罐中进行了酿酒酵母间歇乙醇发酵实验,研究了发酵过程中酵母的主要代谢副产物中有机酸的种类及其对乙醇发酵的影响。结果表明,发酵过程中酵母代谢的主要有机酸是琥珀酸、乳酸和乙酸。3种酸的总量随温度(25~40℃)升高或p H增大(3~6)呈上升趋势,最大值可达5.78 g/L,占产物的23.3%。通过外源投加有机酸实验发现,3种代谢有机酸对酵母抑制作用的大小并不完全由其酸性决定,还与其进入细胞的难易程度等相关。通过外源投加有机酸实验结合发酵过程中去除有机酸实验可以确定,对乙醇发酵的影响由大到小依次为乙酸、琥珀酸和乳酸,且三者之间对乙醇发酵无明显的协同抑制效应。乙酸是发酵过程中产生主要抑制作用的代谢有机酸,2 g/L的乙酸可引起菌体浓度明显下降,4 g/L的乙酸即可引起乙醇得率下降86.7%。     

运动发酵单胞菌232B木薯快速乙醇发酵

以运动发酵单胞菌232B(Z.mobilis 232B)为菌种,木薯为底物进行同步糖化快速乙醇发酵的研究.首先采用Full Factorial设计和最速上升实验确定了培养基成分中的两个显著性因子及其最适浓度:酵母粉4.0g·kg-1,硫酸铵0.8g·kg-1.在最适合的培养基条件下,对木薯料水比和糖化酶用量进行了优化,得到Z.mobilis232B木薯乙醇发酵最佳料水比为1:3,糖化酶浓度为4AGU·g-1淀粉,乙醇发酵4.915g·(kg·h)-1.利用高效液相色谱对发酵液中残糖进行了分析,证明葡萄糖、果糖等单糖已完全被菌体利用,剩余糖多为二糖、三糖等不可发酵的低聚糖.     

海带实验室发酵制取甲烷

以海带为试验材料,研究pH值、温度、微量元素等因素在发酵过程中对甲烷产量的影响.试验在3个pH梯度(pH=6,7,8)、4种温度(T=30,40,50,60 ℃)以及加铁(Fe2O3 6.0 mg)和钙(CaCO3 4.5 mg)微量元素条件下进行.试验结果表明:pH=8、温度T=40℃为海带实验室发酵生产甲烷的最佳试验条件,即总产气量最高;在上述最佳产气条件下,加入微量元素铁和钙可在一定程度上提高产气量,在本试验中,产气量分别提高7.2%和15.3%.     

海带渣降解液中糠醛类物质的去除及对乙醇产率影响分析

利用色谱检测以及葡萄糖溶液模拟发酵,确定了稀酸预处理后海带渣纤维素酶酶解所得糖液中糠醛(2-F)、5-羟甲基糠醛(5-HMF)的含量及其对酵母发酵产乙醇的影响。数据分析结果表明,酶解糖液中的2-F和5-HMF浓度分别为132.4 mg/L和158.5 mg/L,其中2-F对发酵有微弱的促进作用,5-HMF使乙醇产率下降8%。通过蒸发、吸附、萃取、碱化等方法对酶解糖液进行脱毒处理,对比脱毒前后发酵情况发现,Ca(OH)2碱化处理对2-F和5-HMF的去除率分别达到94.4%和77.7%。发酵还原糖乙醇转化率提高14.6%,产率提高10.9%。     

纤维素乙醇木聚糖酶的固体发酵工艺研究

该研究立足于河南天冠企业集团纤维素乙醇项目,以酶解糖化工艺对木聚糖酶的需求为出发点,利用黑曲霉X06作为产酶菌株,采用固体发酵工艺,通过正交设计试验,优化了培养基配方和发酵控制工艺,最优方案:麸皮∶玉米芯=6∶4、硝酸铵4%、尿素1%、磷酸二氢钾0.4%、硫酸镁0.2%、初始含水量65%、初始pH=4.0、温度28℃、环境相对湿度70%、72 h酶活达到10 096.74 IU/g。这一方案在生产中得到进一步放大和优化,所生产的固体木聚糖酶应用在秸秆酶解工艺中,酶解液中木糖含量提高了66.9%。     

Biohydrogen production from soluble condensed molasses fermentation using anaerobic fermentation

Using anaerobic micro-organisms to convert organic waste to produce hydrogen gas gives the benefits of energy recovery and environmental protection. The objective of this study was to develop a biohydrogen production technology from food wastewater focusing on hydrogen production efficiency and micro-flora community at different hydraulic retention times. Soluble condensed molasses fermentation (CMS) was used as the substrate because it is sacchariferous and ideal for hydrogen production. CMS contains nutrient components that are necessary for bacterial growth: microbial protein, amino acids, organic acids, vitamins and coenzymes. The seed sludge was obtained from the waste activated sludge from a municipal sewage treatment plant in Central Taiwan. This seed sludge was rich in Clostridium sp.A CSTR (continuously stirred tank reactor) lab-scale hydrogen fermentor (working volume, 4.0 L) was operated at a hydraulic retention time (HRT) of 3–24 h with an influent CMS concentration of 40 g COD/L. The results showed that the peak hydrogen production rate of 390 mmol H₂/L-d occurred at an organic loading rate (OLR) of 320 g COD/L-d at a HRT of 3 h. The peak hydrogen yield was obtained at an OLR of 80 g COD/L-d at a HRT of 12 h. At HRT 8 h, all hydrogenase mRNA detected were from Clostridium acetobutylicum-like and Clostridium pasteurianum-like hydrogen-producing bacteria by RT-PCR analysis. RNA based hydrogenase gene and 16S rRNA gene analysis suggests that Clostridium exists in the fermentative hydrogen-producing system and might be the dominant hydrogen-producing bacteria at tested HRTs (except 3 h). The hydrogen production feedstock from CMS is lower than that of sucrose and starch because CMS is a waste and has zero cost, requiring no added nutrients. Therefore, producing hydrogen from food wastewater is a more commercially feasible bioprocess.     

木质纤维素制取燃料乙醇菌种的研究

目前,随着石油资源的日益枯竭,寻求一种廉价的、清洁的、可再生的新型能源成为各国能源领域科研人员的一项重要任务.乙醇作为一种工业燃料,具有许多优点,利用生物质制取燃料乙醇技术,越来越受到人们的广泛关注.文章报道了国内外近年来利用木质纤维素稀酸水解液制取燃料乙醇的菌种的研究现状,主要包括木质纤维素稀酸水解液乙醇发酵的酵母菌、细菌及基因重组菌的菌种构建等.     

Hydrogen gas production from distillery wastewater by dark fermentation

The influence of concentration of distillery wastewaters, concentration of inoculum and pH value on hydrogen generation in batch dark fermentation process was studied. Anaerobic digested sludge from municipal purification unit was applied as the source of bacteria mixture. The best specific yield was obtained in system containing 10% v/v of inoculum and 20% v/v of the waste (S₀/X₀ = 2.8), whereas the maximum amount of hydrogen and the highest rate of reaction was achieved in system containing 25% v/v inoculum and 40% v/v of waste (S₀/X₀ = 2.2). The content of generated hydrogen in biogas was always higher than 62%. Maximum amount of generated hydrogen was 1 l H₂/l medium and the rate was 0.12 l/l/h. Liquid metabolites of hydrogen generation process were mainly acetic and butyric acids. Ethanol and propionic acid were in traces. The ratio of HBu/HAc in medium influenced the yield of generated hydrogen.     

Biohydrogen production by extracted fermentation from sugar beet

In the study, the production of biohydrogen by extracted fermentation from sugar beet was evaluated. Effects of initial amount of sugar beet, biomass and particle size of sugar beet on biohydrogen formation were investigated. The hydrogen (H₂) gas was predicted to be 78.6 mL at initial dry weight of sugar beet 24.6 g L^?1 and H₂ yield was calculated as 81.9 mLH₂ g^?1TOC while biomass concentration (1 g L^?1) and particle size (0.3 cm) were constant. The peak H₂ gas volume was predicted to be 139.9 mL at the low particle size of 0.1 cm. Hydrogen gas production potential was predicted as 143.6 mL h^?1. The peak value of 197.9 mLH₂ g^?1TOC was obtained with particle size of 0.1 cm when dry weight of sugar beet and initial amount of biomass was kept constant at 24.6 g L^?1 and 1 g L^?1, respectively.     

The addition of hydrolyzed rice straw in xylose fermentation by Pichia stipitis to increase bioethanol production at the pilot-scale

The pretreatment of agricultural biomass by diluted acid is often employed to facilitate the release of monosaccharide for the subsequent enzyme hydrolysis for lignocellulosic ethanol production. However, furfural and hydroxymethylfurfural are usually generated and markedly decrease the yield of pentose fermentation during this pretreatment. In the present study, the enhancement of lignocellulosic ethanol production was successfully demonstrated at pilot scale with extra addition of hydrolyzed rice straw into pentose fermentation by Pichia stiptis. This way has resulted into the increase of P. stiptis cell mass was shown to play a positive role. The ethanol yield, 0.45 g_p/g_s, with the addition of hydrolyzed rice straw in hemicellulosic hydrolysate from plywood, bagasse and bamboo were increase 20–51% to demonstrate the applicability of this technology in a variety of lignocellulosic ethanol processes due to the efficient conversion of xylose.     

双菌比较优化稻草“液化”发酵产乙醇的研究

利用稻草液化产物为底物,分别采用酿酒酵母和休哈塔假丝酵母发酵生产乙醇,对影响发酵阶段的各因素进行优化,选取最佳菌种完成秸秆到乙醇的转化。结果表明,液化产物经酶解后葡萄糖浓度可达69.5mg/mL,是发酵制备乙醇的良好底物。优化发酵后,酿酒酵母更适合做液化产物的发酵菌种。适宜的发酵条件:初始葡萄糖浓度60~65 mg/mL,温度30℃,pH=6.0,装液量80 mL,接种量10%,发酵时间36 h,在此条件下乙醇得率可达49.3%,能达到理论得率的96.1%,转化率最高为0.27 g/g(乙醇/液化产物)。     

A sequential process of anaerobic solid-state fermentation followed by dark fermentation for bio-hydrogen production from Chlorella sp.

Microalgal biomass has recently been one of the most widely studied feedstocks for bio-hydrogen production, owing to its richness in fermentable components, e.g. polysaccharides and proteins, and high biomass productivity. In this study, biomass of microalga Chlorella sp. TISTR 8411 was converted to hydrogen through a sequential process consisting of an anaerobic solid-state fermentation (ASSF) followed by a dark fermentation. The microalga was grown photoautothrophically in 80-L rectangular glass tanks and then scaled-up to a 240-L open pond for the production of biomass. The highest biomass concentration attained was 4.45 g L⁻¹. The biomass was harvested with over 90% flocculation efficiency at pH 11.5 and a biomass concentration of 2.6 g/L. The sequential process gave a total hydrogen yield (HY) of 16.2 mL/g-volatile-solid (VS), of which 11.6 mL/g-VS was from ASSF. The high HY obtained from the ASSF indicated that it was effective and could be integrated with a conventional hydrogen production process to improve energy recovery from biomass.     

Dark fermentation for H2 production from food waste and novel strategies for its enhancement

Hydrogen is an attractive energy vector that can be obtained through biological methods such as dark fermentation, allowing organic wastes to be used as substrates. This means an advantage compared to other methods since dark fermentation enables the revalorization of waste, such as food waste, with generation and disposal contributing to the current environmental issue. However, the complex composition of food waste and the microbial dynamics involved in dark fermentation have made it difficult to obtain maximum yields. Although several strategies have been evaluated to improve hydrogenogenic systems, the common limitations have been the economic costs and the re-emergence of unwanted microorganisms. Therefore, developing and evaluating novel strategies such as lactate-driven dark fermentation, bioaugmentation with native strains, metabolic engineering, and construction of synthetic microbiomes are innovative proposals to enhance H₂ production from food waste.     

琼胶降解菌的筛选及其在龙须菜乙醇发酵中的初步应用

文章以龙须菜为原料,开展发酵产乙醇的基础研究,主要进行了高效琼胶降解菌的筛选和酶解条件的优化。利用琼胶为唯一碳源筛选出2株琼胶降解能力强的菌株QJ14和Hhjh,通过形态学观察和16s r DNA序列分析,对这两株菌株进行了鉴定,经NCBI数据库比对,确定QJ14为假单胞菌属,Hhjh为白色噬琼胶菌属。用QJ14和Hhjh产生的粗酶液酶解龙须菜酸解糊化液,并对影响酶解效果的因素,如起始p H值、酶解时间、震荡处理、混合酶液比例等进行了优化,结果还原糖产量最高可达29.33 mg/g。通过比较酵母单菌发酵、混合菌发酵与分步酶解发酵,利用顶空气相色谱法(HS-GC法)检测发酵液中乙醇产量,结果表明,酵母单菌发酵和混合菌发酵几乎没有乙醇产生,分步酶解发酵的乙醇产量约为2.36m L/L。     

Hydrogen production from melon and watermelon mixture by dark fermentation

Hydrogen gas production from melon and watermelon mixture by dark fermentation was studied with and without inoculum addition. In this context, hydrogen production performance of natural and external inoculation was compared in batch experiments by varying fruit mixture concentration between 0.74 and 37 g TS/L. Hydrogen production increased by increasing the substrate concentration due to higher initial total sugar content at elevated TS (total solids) concentrations. Hydrogen productivity at 37 g TS/L for natural microflora was 80.62 mLH₂/L_reactor.h. However, this value significantly increased to 351.12 mLH₂/L_reactor.h at same solid concentration when the fruit mixture was externally inoculated with heat treated anaerobic sludge. Most favorable nutrient and inoculum composition for hydrogen gas production were at 37 g TS/L. Moreover, the presence of the natural microflora in the fruit mixture led to less inoculum requirement and contribution for hydrogen formation.