外源葡萄糖对麦秸厌氧发酵产沼气的影响

为进一步阐释混合厌氧发酵的内在机制,在中温(35±1)℃条件下,以麦秸为原料,以葡萄糖为外源易分解有机碳,采用批式发酵方式,进行了葡萄糖不同添加量和不同添加方式对秸秆厌氧发酵产沼气影响试验。结果表明,在试验初始添加葡萄糖可提高日产气量,但葡萄糖添加量太少对提高秸秆总固体(TS)产气量无促进作用,当葡萄糖添加量为秸秆TS质量的6%时获得最大秸秆TS产气量,为303.13 m L·g-1,继续增加葡萄糖添加量,秸秆TS产气量反而降低;在秸秆厌氧发酵日产气量下降阶段一次性或者分次添加葡萄糖对促进秸秆厌氧发酵产沼气均无效果,仅在试验初始一次性添加秸秆TS质量6%的葡萄糖时对秸秆厌氧发酵产沼气有促进作用,秸秆TS产气量较对照提高9.24%;添加葡萄糖对秸秆厌氧发酵过程产气中甲烷含量无明显影响,但提高累积产气中甲烷平均含量,且在日产气量下降后添加葡萄糖的效果更好,但这种促进效果与对照间差异并不显著。综合以上结果,在试验初始一次性添加秸秆TS质量6%的葡萄糖可以获得最佳的产气效果。     

麦秸与奶牛场废水高固体混合厌氧发酵产甲烷研究

在实验室条件下,以麦秸和奶牛场废水为原料,设计麦秸与奶牛场废水质量比1∶4(T1)、1∶3(T2)和1∶2(T3)以及对照(麦秸与水质量比1∶4(T4))4个处理,研究发酵过程中日产气量、甲烷含量、发酵前后麦秸理化特性和结构的变化.结果表明,奶牛场废水与麦秸在中温、高固体条件下,厌氧发酵可以正常进行,且产气期延长2周以上,对甲烷含量的影响不大;厌氧发酵初始TS浓度对系统产气的影响较大,麦秸产气量随TS浓度的增加而降低,以T1的产气效果最好,麦秸TS产气量为0.41 L.g-1,较T4提高了17.14%,平均甲烷含量为48.78%;厌氧发酵后,麦秸半纤维素含量大幅降低,纤维素含量少许降低,降低幅度均为T1>T2>T4>T3,木质素含量稍有增加,各处理间无显著差异(P>0.05);FTIR和XRD的结果表明,厌氧发酵后,麦秸纤维素结晶区的相对含量增加,混合发酵可以促进厌氧微生物对麦秸纤维素结晶区的破坏.将麦秸与奶牛场废水(质量比)1∶4混合发酵产沼气是可行的,且促进了厌氧微生物对麦秸有机物的分解破坏,提高了麦秸产气量.     

基于木质素生物降解的堆肥化接种剂开发

选取由农林废物堆肥中筛选出的木质素降解优势土著微生物枯草芽孢杆菌(Bacillus subtilis)、铜绿假单孢菌(Pseudomonas aeruginosa)、黑曲霉(Aspergillus niger)、简青霉(Penicillium simplicissim)、栗褐链霉菌(Streptomyces badius),依据PLFA-PLS定量分析所得堆肥化2次发酵期有效的木质素降解微生物群落组成比例混合接种至稻草基质发酵瓶中,做1组L9(34)正交试验以优化混合比例,期望开发1种基于木质素降解的高效堆肥化接种剂.试验结果表明:混合菌剂具有较强的木质素降解能力,其对木质素的降解是木质素过氧化物酶、锰过氧化物酶、漆酶、纤维素酶和半纤维素酶共同作用的结果;当按照个数比细菌∶放线菌∶真菌为85∶5∶ 10,枯草芽孢杆菌∶铜绿假单孢菌为55∶25,黑曲霉∶简青霉为2∶1配比时,木质素、纤维素、半纤维素降解率最高,分别达到22.13%,48.97%和55.93%;在不灭菌前提下,按此配比接入菌剂,其木质素、纤维素、半纤维素降解率分别比不接菌剂发酵稻草提高19.16,38.25和46.30百分点.     

添加蚓粪对玉米秸秆厌氧发酵产气特性的影响

以玉米秸秆为原料,总固体(TS)含量为50g.kg-1,采用中温35℃批式发酵,考察了添加蚓粪对玉米秸秆厌氧发酵产气的影响。结果表明:玉米秸秆单独发酵时,单位TS产气量为333.3mL.g-1,甲烷产量为202.0mL.g-1,并在反应初期出现酸化现象;蚓粪与玉米秸秆TS质量比为1:1进行发酵时,单位TS产气量为400.0mL.g-1,甲烷产量为269.6mL.g-1,相对于玉米秸秆单独厌氧发酵分别提高了20.0%和35.5%,且反应过程中未出现酸化现象。说明蚓粪适合作为玉米秸秆厌氧发酵产气的添加剂。     

不同预处理方式对玉米秸秆结构及产气特性的模拟研究

以玉米秸秆为原料,在25℃条件下,分别采用沼液及不同含量的NaOH溶液对秸秆进行预处理,研究NaOH投加量与秸秆纤维结构、预处理料液理化性质以及产能特性之间的关系。结果表明,采用4 mg·g-1NaOH溶液预处理7 d后,料液中COD浓度已基本稳定,溶液pH值在7~8之间,可直接装罐发酵。利用扫描电镜观测预处理后秸秆结构变化状况,发现经4 mg·g-1NaOH溶液预处理后的秸秆表层结构粗糙、多孔,有助于厌氧微生物与可发酵底物的接触,产气量是未经预处理玉米秸秆的5.5倍,其干物质产气率为225.8 mL·g-1。综合考虑产气效率、生产成本及工程操作,采用4 mg·g-1NaOH溶液预处理秸秆更利于工程推广应用。     

氨化预处理对生物质秸秆厌氧发酵的影响

为探明氨化预处理对小麦秸秆干式厌氧发酵产气量影响的内在原因,采用傅立叶变换红外光谱（FTIR）、扫描电子显微镜（SEM）、视频光学接触角测定仪（GBX）、热重分析（TGA）等方法,对氨化处理前后小麦秸秆中纤维结构的变化进行了多方面研究。结果表明,氨化预处理使小麦秸秆纤维部分官能团发生断裂,表层的亲水性增加,秸秆的热稳定性提高,并且氨化作用对纤维结构的破坏,有利于厌氧微生物接触到更多的可发酵物质,提高了秸秆的利用率,也表明小麦秸秆纤维结构的变化是厌氧发酵产气量提高的主要原因。     

过表达分支酸歧化酶编码基因ARO7对酿酒酵母抑制物耐受性的影响

利用纤维素原料生产乙醇一直是国内外研究的热点,但纤维素预处理过程产生的弱酸、酚类和糠醛等抑制物对酿酒酵母细胞生长和乙醇发酵具有抑制作用,因此,提高酿酒酵母细胞的环境胁迫耐受性是提高纤维素乙醇发酵效率的重要手段之一.对芳香族氨基酸代谢途径中分支酸歧化酶基因ARO7的过表达对酿酒酵母在胁迫条件下细胞生长和乙醇发酵性能的影响进行研究.结果显示,过表达ARO7的重组菌株在含有5.0 g/L乙酸的平板中生长优于对照菌株;在含有5.0 g/L乙酸的发酵培养基中进行乙醇发酵,过表达ARO7的重组菌株的发酵效率高于对照菌株,在菊芋秸秆水解液中ARO7过表达重组酵母菌株乙醇得率由对照的0.44 g/g提高到0.47 g/g葡萄糖,乙醇生产强度提高了22.38%.以上表明,ARO7的过表达可提高酿酒酵母在抑制物存在条件下纤维素乙醇的发酵效率.     

不同时间NaOH预处理对玉米秸秆中温厌氧发酵的影响

通过自行设计的厌氧发酵装置,采用0‰、4‰和12‰的NaOH溶液对玉米秸秆预处理3、7、14、21 d和28 d,研究不同时间NaOH预处理对玉米秸秆中温(35℃)厌氧发酵的影响,旨为玉米秸秆在沼气生产中的高效应用提供理论依据。结果表明,采用NaOH预处理可以提高玉米秸秆中温厌氧发酵时的产气量和产气速率,其中4‰NaOH预处理的效果好于0‰和12‰,而且以预处理7 d的效果最好。以16.0 g玉米秸秆为发酵原料时,111 d产气停止,总产气量为7 411.00 m L,若以累积产气量达到总产气量的90%以上作为发酵完成标准,则78 d发酵完成,可累积产气6 672.60 m L,日均产气85.55 m L,干物质累积产气量为417.04 m L·g~(-1)。最优组合预测模型同样显示,4‰NaOH预处理效果最好,最佳预处理时间为9.48 d,84.00 d发酵完全,产气速率为60.29 m L·d-1,最大干物质累积产气量为316.52 m L·g~(-1),这与实测值具有良好的一致性。综合判断,在玉米秸秆中温厌氧发酵时,通过适当延长预处理时间来减少碱液用量是可行的,其中以4‰NaOH预处理9.48 d效果最好。     

发酵牛粪和造纸干粉对土壤中多环芳烃降解的影响

运用泥浆反应法研究添加发酵牛粪和造纸干粉对土壤中多环芳烃(PAHs)降解的影响.试验按水土比2:1制成泥浆反应器,设置对照、添加2.5%发酵牛粪和添加2.5%造纸干粉等3个处理,25～28℃摇床培养,分别于10、20、30 d采样测定土壤中多环芳烃降解菌的数量和多环芳烃含量.结果发现,所有处理土壤中多环芳烃的含量均随培养时间的延长而逐渐降低,而添加发酵牛粪和造纸干粉均有利于提高土壤中多环芳烃降解菌的数量,在培养30 d后土壤中多环芳烃的降解率分别从对照处理的19%显著提高到37%和35%(P<0.05).结果还发现,多环芳烃分环降解率随苯环数增加而下降,培养30 d后土壤中2环多环芳烃的降解率达95%以上,3环多环芳烃的降解率为50%左右,对照处理4～6环多环芳烃的降解率为7%～13%,而添加发酵牛粪和造纸干粉处理土壤中4～6环多环芳烃的降解率显著提高到21%～28%(P<0.05),但对2～3环多环芳烃的降解无明显影响,表明这两种物质对土壤中多环芳烃降解的影响关键在于促进高环多环芳烃降解菌的生长繁殖及降解活性.     

秸秆的不同预处理方法对发酵产氢的影响

比较研究了化学预处理、生物预处理以及化学与生物结合预处理方法对秸秆发酵产氢的影响.结果表明,预处理可以将秸秆中相当一部分纤维素和半纤维素水解生成还原糖,其中1%H2SO4对秸秆的水解效果最好,50 g秸秆水解可产生16.05 g还原糖;经过NaOH和生物结合预处理后的秸秆发酵产氢效果最好,其产氢能力为21.04 mL g-1,是未经预处理秸秆的75倍;最高氢气浓度为57.3%,是未经预处理秸秆的96倍;其产氢的最适pH为4.5～6.0,最佳底物浓度为45～55 g L-1;其发酵过程中的挥发性脂肪酸(VFAs)以乙酸和丁酸为主.图4表4参15     

低浓度溶解氧下猪粪固体有机物水解产酸研究

本文以猪粪为发酵原料,通过批式实验研究不同溶解氧(DO)浓度(0—0.26 mg.L-1)、发酵时间(3—12 d)和挥发性固体(VS)浓度(11.14—111.35 g.L-1)对猪粪固体水解酸化过程的影响,确定了低DO浓度下固体有机物优化水解产酸工艺条件:中温35℃,初始VS浓度37.11 g.L-1,初期的DO浓度0.1—0.26 mg.L-1.在此条件下,发酵时间3 d,DO浓度下降到0.10 mg.L-1以下.猪粪发酵液pH值由7.45±0.10降低到5.86±0.17,VS降解率(25.67±1.20)%,挥发性脂肪酸(VFA)中乙酸(3895±91)mg.L-1、丙酸(2313±82)mg.L-1、正丁酸(1361±17)mg.L-1、正戊酸(540±11)mg.L-1.优化条件下的猪粪水解酸化液进行厌氧产甲烷发酵,发酵10 d内产气停止,低溶解氧水解酸化和厌氧产甲烷发酵累计时间仅为13 d,甲烷体积分数(69.5±0.2)%,VS产气率为(0.282±0.011)L CH.4g-1VS.研究结果表明,适当延长发酵时间能够增加VFA中乙酸的含量,初始VS浓度差异对发酵液VFA浓度和VS降解率的影响较显著,低溶解氧能够促进猪粪固体有机物水解过程.     

Effect of different gas releasing methods on anaerobic fermentative hydrogen production in batch cultures

Decreasing hydrogen partial pressure can not only increase the activity of the hydrogen enzyme but also decrease the products inhibition, so it is an appropriate method to enhance the fermentative hydrogen production from anaerobic mixed culture. The effect of biogas release method on anaerobic fermentative hydrogen production in batch culture system was compared, i.e., Owen method with intermediately release, continuous releasing method, and continuous releasing+ CO₂ absorbing. The experimental results showed that, at 35°C, initial pH 7.0 and glucose concentration of 10 g·L^-1, the hydrogen production was only 28 mL when releasing gas by Owen method, while it increased two times when releasing the biogas continuously. The cumulative hydrogen production could reach 155 mL when carbon dioxide in the gas stream was continuously absorbed by 1 mol·L^-1 NaOH. The results showed that acetate was dominated, accounting for 43% in the dissolved fermentation products in Owen method, whereas the butyrate predominated and reached 47%–53% of the total liquid end products when releasing gas continuously. It is concluded that the homoacetogenesis could be suppressed when absorbing CO₂ in the gas phase in fermentative hydrogen production system.     

皇竹草厌氧发酵产沼气特性

在中温(35℃)条件下,采用批量厌氧发酵对生长期为35 d和68 d的皇竹草的发酵特性进行研究.实验结果表明,两组不同生产期的皇竹草C/N均较低,分别为14.75和17.52.经过45 d的厌氧发酵处理,生长期为35 d的皇竹草产气率为243.77ml.g-1VS,在第1天和第15天出现两个产气高峰,第45天的产气结束;生长期为68 d的皇竹草产气率为247.06 ml.g-1VS,出现4次产气高峰,第45天日产气量为512ml.生长期为35 d和68 d的皇竹草发酵液中乙酸、丙酸、丁酸含量分别为48.48%—72.71%、5.64%—22.99%、6.84%—26.71%和42.51%—64.17%、5.83%—34.20%、10.98%—34.41%,丙酸型发酵和丁酸型发酵交替进行.发酵液的pH值均先降低后升高最后保持相对稳定.皇竹草适合作为沼气发酵的原料加以利用.     

Rapid start-up of mesophilic dry anaerobic digestion of kitchen waste in a continuous stirred tank reactor (CSTR)

Under mesophilic conditions (37 °C), a bench-scale experiment of dry fermentation start-up using kitchen waste was conducted in a fed-batch single phase reactor over a period of 40 days. The results showed that (1) comparing biogas production, efficiencies, and methane concentrations, three apparent different stages emerged: adaption, growth, and stability; (2) in adaption and growth stages, daily biogas production was 0–0.2 L/day and 0.2–0.4 L/day, respectively, and the concentration of methane in the biogas was 22.91% and 48.79%, respectively, with a biodegradation rate of approximately 34.72% in the adaption phase and 27.60% during the growth phase; (3) in the stability stage, the biogas production efficiency attained the maximal level and stabilized at approximately 0.6–0.4 L/day and the concentration of methane was 54.32%. Furthermore, the pH fell to 4.15, and the concentration of chemical oxygen demand increased from 51.139 to 119.295 mg/ml.     

加饲不同数量的沼液对育肥猪的影响

用4组共32头仔猪进行了三种不同喂量的沼液饲养试验。试验结果表明,在饲料消化能为12.1MJ/kg、粗朊10％的营养水平下,按饲料量(风干重)的1.5倍加饲沼液对育肥猪有显著的增重效果(P<0.05),平均比对照净增20.6％,饲料利用率提高17％,育肥期缩短25％左右,有明显的生态效益和经济效益。     

木质纤维素生产燃料乙醇的关键技术研究现状

木质纤维素是自然界广泛存在且廉价的可再生资源.其主要成分纤维索、半纤维素是潜在的燃料乙醇生产原料.虽然由木质纤维素生产燃料乙醇的技术路线已具可行性,但存在着具体工艺环节复杂、生产能耗高等局限,严重阻碍了其规模化生产.目前纤维素燃料乙醇生产主要围绕预处理、酶解、发酵三大关键步骤进行技术攻关,其中预处理的能耗和效率、发酵过程的五碳糖利用等问题成为该工艺的重要制约因素.本文在综述国内外纤维素乙醇生产关键步骤的基础上,着重分析了各种物理、化学和生物预处理的优缺点以及新兴的预处理思路,归纳了各类纤维素乙醇生产菌的特点,包括耐高温和五碳糖的利用,并介绍了当前主要的发酵方式和优化措施,以期为木质纤维素生产乙醇提供新的研究思路.表5参86     

沼气发酵在复合农业生态系统中的作用

沼气发酵系统是复合农业生态系统中物质循环和能量转化的枢纽。它以农业有机废弃物为原料，经厌氧消化，生产出高效、洁净、多用途的燃料、饲料和肥料。本文论说了开展沼气发酵对保护农村生态环境。促进生态农业发展所具有的重要意义，提出了目前我国沼气发展过程中存在的一些问题和今后应采取的措施。     

Impact of Ni(II), Zn(II) and Cd(II) on biogassification of potato waste

A study was conducted on anaerobic digestion of potato waste and cattle manure mixture, inoculated with 12% inoculum and diluted to 1:1 substrate water ratio at 37 +/- 1 degrees C. Initially pH of substrate was found to be 4.5 to 5.0. Lime and sodium bicarbonate solutions were employed to adjust the pH to 7.5. Biogas production continued up to 10 and 7 days, when lime and sodium bicarbonate solutions were used to adjust the pH, respectively. Biogassification potential was studied in response to different ratio of waste and cattle manure. Biogas production rate was higher when potato waste and cattle manure were used in 50:50 ratio. Effect of two different concentrations (2.5 and 5.0 ppm) of three heavy metals viz. (Ni (II), Zn (II) and Cd (II)) on anaerobic digestion of substrate (potato waste--cattle manure, 50:50) was studied. At 2.5 ppm, all the three heavy metals increased biogas production rate over the control value. The percentage increase in biogas production over the control was highest by Cd, followed by Ni and Zn. In all the treatments, methane content of biogas increased with increase in time after feeding. Various physico-chemical parameters viz. total solids, total volatile solids, total organic carbon and chemical oxygen demand considerably declined after 7 days of digestion and decline was greater in presence of heavy metals as compared to control. The physico-chemical parameters revealed maximum decrease in the presence of 2.5-ppm concentrations of heavy metals with the substrate. Among all the three heavy metals employed in the study, Cd++ at 2.5 ppm was found to produce maximum biogas production rate. The use of three heavy metals to enhance biogas production from potato and other horticultural waste is discussed.     

Effectiveness of aerobic pretreatment of municipal solid waste for accelerating biogas generation during simulated landfilling

Effect of aerobic pretreatment of MSW on landfill gas generation was investigated. Volatile solid (VS) loss of MSW is an effective and comparable indicator. Chinese MSW requires at least a reduction of VS about 27% (w/w) prior to disposal. Aerobic pretreatment of MSW reduced lag phase more than 90% before methanogenesis. Aerobic pretreatment degree influences quantity of gas generation. This study evaluates the effectiveness of aerobic pretreatment of municipal solid waste (MSW) on reducing lag phase and accelerating biogas generation. Aerobic pretreatment degree (APD) was determined on the basis of reduction in volatile solids (VS) on a wet weight basis. In this study, intermittent aeration (IA) was applied to three reactors as a main aeration mode; since a single reactor was operated under continuous aeration mode. However, the purpose of the experiment was to reduce VS content of waste, irrespective of the comparison between aeration modes. Fresh MSW was first pretreated aerobically with different aeration rates (10, 40, 60 and 85 L/min/m³) for the period of 30–50 days, resulting in VS-loss equivalent to 20%, 27%, 38% and 53% on w/w basis for the wastes A1, A2, A3 and A4, respectively. The cumulative biogas production, calculated based on the modified Gompertz model were 384, 195, 353, 215, and 114 L/kg VS for the wastes A0, A1, A2, A3 and A4, respectively. Untreated waste (A0) showed a long lag phase; whereas the lag phases of pretreated MSW were reduced by more than 90%. Aerobically pretreated wastes reached stable methanogenic phase within 41 days compared to 418 days for untreated waste. The waste mass decreased by about 8% to 27% compared to untreated MSW, indicative that even more MSW could be placed in the same landfill. The study confirmed the effectiveness of aerobic pretreatment of MSW prior to landfilling on reducing lag phase and accelerating biogas generation.