一株纤维素降解菌的筛选及其在沼气应用中的研究

利用实验室保存的细菌、真菌和从牛粪、猪粪中分离出来的多株菌株,对秸秆纤维素进行降解试验,从而筛选出了能够降解秸秆纤维素(降解率为43.75%)的优势菌株.用几株降解效果较理想的菌株处理秸秆,对处理后的秸秆进行沼气发酵,通过高效气相色谱仪对沼气成分进行分析,发现从牛粪中筛选出的N2菌株效果较好,发酵2周后,其产气中甲烷含量为62.48%(体积分数,下同),二氧化碳含量为31.83%,氮气含量为2.11%.通过生理生化鉴定,初步鉴定N2菌株为枯草杆菌(Bacillus subtilis).     

羊粪沼气发酵过程中的纤维素酶酶活力与沼气产气量的关系研究

试验研究了在羊粪沼气发酵过程中纤维素酶酶活力与沼气产气量的变化关系.结果表明:在羊粪沼气发酵过程中,纤维素酶酶活力的大小与沼气产气量随时间表征出一致的变化趋势,但产气量的变化在时间上要落后于纤维素酶酶活力的变化,即在纤维素酶达到一峰值的下一时刻,产气量达到一峰值.     

羊粪沼气发酵产气潜力的试验研究

在平均室温22．9℃的条件下，以羊粪为原料，进行批量发酵产沼气的试验研究。结果表明，在料液TS浓度为8．65％时，羊粪发酵产沼气潜力为214．47ml／g。     

温度对低温选育复合菌系产甲烷活性的影响

通过低温驯化,以甲烷含量及产气量为研究指标,选育出一组稳定的低温、高效产甲烷复合菌系.14.0±0.5℃培养,15天时甲烷纯度达到63.3％、产气量为139mL,分别较样品提高386.0％和18.7％.SPSS分析表明,温度对产气量及甲烷含量的影响达到显著水平,根据回归方程计算得到复合菌系的最适产气温度为1 3.0～22.0℃.通过对产甲烷活性抑制与恢复性研究,结果表明30C对复合菌系中的关键微生物的抑制作用具有不可恢复性,推测复合菌系中的微生物多为专性嗜冷产甲烷古菌.10％为该复合菌系最适接种量,8％为沼气发酵过程复合菌系的最佳底物浓度,且增加底物浓度接近干法水平复合菌系仍然可以完成发酵正常产气.     

低温产甲烷复合菌系的选育及产甲烷活性影响

一引言目前国内沼气发酵以中、高温为主,低温研究尚处探索阶段。有研究者认为低于20℃沼气发酵速度急剧下降。在我国北方由于低温的限制,同样数量的沼气原料产气量往往不及夏季的1/3,严重限制了沼气在我国北方推广。低温季节进行沼     

木质纤维素稀酸水解液乙醇发酵的新方法

为了降低木质纤维素水解液发酵抑制剂对乙醇发酵的负影响,采用混合菌种对木质纤维素稀酸水解液乙醇发酵方式进行了研究。对批式发酵、补料批式发酵和间隔补料批式发酵3种发酵方式进行了比较。实验结果表明,间隔补料批式发酵可以有效地减弱水解液中抑制因子对菌种的影响,乙醇产量明显高于其他两种发酵方式,利用酿酒酵母(Saccaromyces cerevisiae 2.535)和嗜鞣管囊酵母(Pachysolen tannophilis ATCC 32728)混合发酵,乙醇产量最终达到14.4g/L,乙醇产率(Yp/s)为0.47g/g,相当于最大理论产率的92.2%。利用酿酒酵母和重组大肠杆菌混合菌种发酵,乙醇产量达到了14.5g/L。对木质纤维素稀酸水解液采用间隔补料批式乙醇发酵方法,可进一步减少抑制剂对乙醇发酵的影响,使发酵顺利进行。     

水葫芦汁中温沼气发酵的实验研究

以鲜水葫芦汁为原料,在30℃恒温下,采用批量发酵工艺,进行发酵产沼气实验,测定发酵产沼气与时间的关系.实验结果表明,鲜水葫芦汁COD的降解率达到86%;鲜水葫芦汁发酵在第10天后达到稳定值,并持续产气25 d;对发酵过程中所产气体进行分析,发现甲烷含量最高能达到60%左右.因此,水葫芦是一种良好的发酵原料.     

纤维素降解及产氢影响因素的分析

试验研究了纤维素的降解过程及其糖化液的产氢情况.试验结果表明,影响纤维素降解的因素的主次顺序:酸的质量分数＞降解温度＞降解时间.以降解后的纤维素作为R3的营养底物时,R3的产氢效能并不是很理想,在乙酸质量分数为20%、降解温度为70℃、降解时间为1.5 h,盐酸质量分数为20%、降解温度为70℃、降解时间为1 h的条件下,氢气产量均达到最大值(20 ml).虽然氢气总产量不高,但是研究结果表明,纤维素糖化液仍有产氢潜力,有必要作进一步的研究.     

青霉菌对秸秆复合菌系好氧发酵的影响

文章研究了青霉菌对玉米秸秆复合菌系好氧发酵的影响以及青霉菌与其他微生物间的相互作用。研究结果表明:添加青霉菌可以提高秸秆复合菌系对木质纤维素的降解;当青霉菌的添加量超过0.3%时,其提高效果与添加量为0.3%时没有显著差异;好氧发酵结束后,添加青霉菌试验组的总腐殖酸、胡敏酸和富里酸含量均高于对照组,青霉菌添加量为0.3%的试验组的总腐殖酸、胡敏酸、富里酸与胡富比最高,分别为521.75,331.64,190.11 g/kg和1.74;添加青霉菌可以提高漆酶活性,降低木质素过氧化物酶活性;青霉菌与复合菌系存在竞争关系,但添加青霉菌改变了好氧发酵过程中复合菌系的微生物群落结构;在好氧发酵末期,真菌优势菌群为子囊菌门(Ascomycota)和担子菌门(Basidiomycota),细菌优势菌群为变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和拟杆菌门(Bacteroidetes)。     

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%。     

以秸秆和厨余垃圾为原料发酵产甲烷工艺的优化

利用响应曲面法研究了秸秆与厨余垃圾混合厌氧发酵产甲烷的二次回归模型和工艺条件。选取原料配比、原始C/N、TS浓度为参考因素,采用3因素3水平的试验设计手段进行预测,在原料配比(秸秆∶厨余)为1.29∶1,C/N为20.42,TS浓度为10.07%时,甲烷的总产气量达到最高值,为21431.7mL,产气率为126.06mL/g。利用响应曲面法对结论进行优化检验,结果表明,实际值与理论值误差很小,工艺参数可用于实际应用中。     

乙酸对发酵产氢过程的抑制影响

以甲酸为发酵原料进行试验,控制发酵料液的pH在4.8左右,试验共分为10组,每组中分别含有不同浓度的乙酸作为抑制剂。采用批量发酵工艺,进行厌氧发酵产氢,研究乙酸在产氢过程中的抑制作用。由试验可知,当乙酸浓度≥7000mg/l时,抑制作用显著,使产气停止。     

Grass for biogas production: The impact of silage fermentation characteristics on methane yield in two contrasting biomethane potential test systems

Grassland biomass is likely to be harvested and stored as silage to ensure a predictable quality and a constant supply of feedstock to an anaerobic digestion facility. Grass (Phleum pratense L. var. Erecta) was ensiled following the application of one of six contrasting additive treatments or a 6 h wilt treatment to investigate the effects of contrasting silage fermentation characteristics on CH₄ yield. In general, silage fermentation characteristics had relatively little effect on specific CH₄ yield (from 344 to 383 Nl CH₄ kg⁻¹ volatile solids). However, the high concentrations of fermentation products such as ethanol and butyric acid following clostridial and heterofermentative lactic acid bacterial fermentations resulted in a numerically higher specific CH₄ yield. While the latter fermentation products of undesirable microbial activity have the potential to enhance specific CH₄ yield, the numerically higher specific CH₄ yield may not compensate for the associated total solids and energy losses during ensiling.     

辣椒厌氧发酵产H2和CH4的试验研究

以辣椒为原料,以实验室长期驯化的猪粪发酵残留物为底物的混合厌氧消化污泥作为接种物,在常温下进行批量发酵,发酵料液体积400 ml,RHT=86 d.TS质量分数为6.36%时,进行厌氧发酵产H2,产H2结束后使用NaOH溶液调节pH值为7.42,继续发酵产CH4.结果表明:辣椒产氢潜力(TS)为103.0L/kg,VS产氢潜力145.7 L/kg;TS产甲烷潜力为254.6 L/kg,VS产甲烷潜力为276.9 L/kg,其TS能量利用潜力达2 222.4 kJ/kg.     

Thermophilic dark fermentation of acid hydrolyzed waste ground wheat for hydrogen gas production

Batch dark fermentation experiments were performed to investigate the effects of biomass and substrate concentration on bio-hydrogen production from acid hydrolyzed ground wheat at 55 °C. In the first set of experiments, the substrate concentration was constant at 20 g total sugar L⁻¹ and biomass concentration was varied between 0.52 and 2.58 g L⁻¹. Total sugar concentration was varied between 4.2 and 23.7 g L⁻¹ in the second set of experiments with a 1.5 g L⁻¹ constant biomass concentration. The highest cumulative hydrogen formation (582 mL, 30 °C, 1 atm), formation rate (5.43 mL h⁻¹) and final total volatile fatty acid (TVFA) concentration (6.54 g L⁻¹) were obtained with 1.32 g L⁻¹ biomass concentration. In variable substrate concentration experiments, the highest cumulative hydrogen (365 mL) and TVFA concentration (4.8 g L⁻¹) were obtained with 19.25 g L⁻¹ initial total sugar concentration while hydrogen gas formation rate (12.95 mL h⁻¹) and the yield (200 mL H₂ g⁻¹ total sugar) were the highest with 4.2 g L⁻¹ total sugar concentration.     

The impact of price variation on the production of crude oil and natural gas

This paper is directed at examining the impact of changing prices on the level of production of crude oil and natural gas in the United States. By using a cross correlation test for unidirectional causality, it is clearly demonstrated that for both crude oil and natural gas, domestic production is affected by changing prices. The implications are clear. The decontrol of the price of crude oil and the deregulation of natural gas prices will lead to additional production in the near term.     

Possibility of hydrogen production during cheese whey fermentation process by different strains of psychrophilic bacteria

The aim of this study was to determine the possibility of applying psychrophilic bacteria for hydrogen production in whey biofermentation process. Experiments were conducted in 500-mL anaerobic respirometers at a temperature of 20 °C. The initial organic load of fermentation tanks reached 10 g COD/L. Depending on the experimental variant, analyses were carried out for psychrophilic bacteria isolated from underground water and from demersal lake water that represented Gammaproteobacteria class – Rahnella aquatilis (9 strains) and Firmicutes phylum: Carnobacterium maltaromaticum, Trichococcus collinsii and Clostridium algidixylanolyticum. The effectiveness of biogas production was diversified and strain-specific, ranging from 126.48 to 4737.72 mL/g bacterial biomass. The highest concentration of H₂ in biogas, ranging from 65.15% to 69.12% and effectiveness of H₂ production from 1587.47 to 3087.57 mL/g bacterial biomass, were determined for R. aquatilis strains isolated from the demersal lake water. The lowest H₂ concentration in the gaseous metabolites, i.e. 15.46% to 20.70%, was noted for bacteria of the phylum Firmicutes.