种泥预处理和发酵温度对暗发酵产氢的影响研究进展

生物质暗发酵产氢不仅可以处理有机废物,同时可以获得清洁能源,实现了废物资源化利用。然而产氢种泥中大量耗氢菌的存在会导致暗发酵氢气产量低等问题,因此种泥预处理是暗发酵产氢的必需条件。随着暗发酵产氢基质的多样化,产氢种泥的预处理方法也不断发展。对近十年来产氢种泥预处理方法的发展进行了综述,并且结合发酵温度,讨论了种泥预处理方法和发酵温度两方面条件对暗发酵产氢的影响,并对该研究方向提出了展望,以期为后续暗发酵产氢的进一步研究提供参考。     

污泥与餐厨垃圾发酵产氢种泥预处理方法比较

以剩余污泥和餐厨垃圾作为混合基质进行厌氧发酵产氢批式试验,比较六种常用的产氢种泥预处理方法[热处理、化学抑制剂2-溴乙基磺酸钠(BESA)处理、酸处理、碱处理、连续曝气、重复曝气]对产氢的影响。结果表明,未经预处理的种泥氢气产率最低,且有明显的吸氢和产甲烷现象。BESA处理、酸处理、连续曝气和重复曝气种泥产氢效果较好,其中重复曝气预处理种泥氢气产率最高,为86.9 ml-H2/g-VSadded,对产甲烷菌有明显抑制。热处理和碱处理种泥产氢效果较差,反应后期出现吸氢反应并有明显的甲烷累积现象。发酵产氢过程中p H值从中性下降到5.0左右,对产甲烷菌活性也具有一定的抑制作用。     

发酵产氢菌株的筛选及影响因素研究

采用双层平板法从污泥池中筛选出一株产氢较高的发酵菌株,经生理生化鉴定表明,分离菌株初步鉴定为消化链球菌属(Peptostreptococcus).研究静态培养条件下葡萄糖、pH、温度及和酵母膏对菌株产氢的影响及不同发酵时间段的产氢情况.结果表明,在葡萄糖浓度20.0 g/L,pH 7.0,温度37 ℃和酵母膏2.0 g/L时,产氢量达21.07 mmol/L,为初始培养条件下的4.14倍.同时,在24～36 h时间段产氢率达到最高,为0.44 mmol/(L·h),并且在60 h时产氢量达到最大累计产氢量的89.2%.     

微生物发酵产氢的影响因素分析*

随着环保要求的愈益严格和化石能源的日益短缺,氢作为清洁高效的可再生能源日益受到人们的重视。微生物发酵产氢可以利用可再生的生物质,符合可持续发展的要求。针对影响微生物发酵产氢的因素,总结了国内外在该领域的研究成果,重点介绍了产氢微生物、营养物、产物和工艺操作条件等方面对发酵产氢的影响,同时还阐述了以有机废弃物为基质时的发酵产氢影响因素。     

预处理对泔脚发酵产氢的强化研究

采用热(80℃,15 min)预处理的城市生活垃圾厌氧消化污泥为接种物,考察了不同预处理方法对泔脚中温(36℃)批式发酵产氢的影响。Gompertz模型拟合结果表明:微波850 W,4 min与pH9.0下预处理泔脚的发酵产氢延迟时间λ、最大比产氢率、产氢率、生物气中氢气的最高体积分数分别为:3.47 h,9.43 mL/(g.h),186.23 mL/g及46.0%时,具有更大的产氢优越性。泔脚的发酵产氢过程也是一个酸化过程,发酵产氢结束后,4个预处理方案的发酵产氢余物的pH在4.40~5.00之间,pH均有较大幅度的下降。     

厌氧产氢微生物研究进展

微生物是生物制氢的核心。本文论述了通过厌氧代谢途径产氢的微生物种类及高效产氢微生物选育和应用的研究趋势, 其中重点论述了中温和嗜热厌氧产氢微生物的产氢能力、底物利用范围及代谢特性, 简述了嗜热一氧化碳营养型产氢菌的种类及代谢特点。     

微生物产氢研究的进展

氢能由于其清洁、高效、可再生的特点而成为一种最有吸引力的化石燃料的替代能源。与传统的热化学和电化学制氢技术相比,生物制氢具有低能耗、少污染等特点。本文主要对各种微生物的生物产氢方法作一综合概括,着重介绍光合紫色非硫细菌(PNS)产氢研究的最新进展。     

酒色着色菌利用产酸克雷伯氏菌发酵废液产氢

研究了酒色着色菌(Chromatium vinosum DSM185)利用产酸克雷伯氏菌（Klebsiella oxytoca HP1）发酵产氢废液进行光发酵和暗发酵产氢的可行性,以达到对产氢底物的充分利用和对产氢废液的进一步处理。研究结果表明C.vinosum可以利用K.oxytoca的发酵废液进行光发酵产氢和暗发酵产氢。C.vinosum发酵产氢后废液中残余还原糖和主要有机酸（丁酸）的含量明显降低,发酵产氢的最佳pH为6.5,添加0.1%(W/W)NH₄Cl能促进产氢。在光照条件下丁酸利用率可达54.38%,产氢量达36.97 mL/mg;在黑暗条件下丁酸利用率可达36.01%,产氢量达37.50mL/mg。     

酒色着色菌利用产酸克雷伯氏菌发酵废液产氢

研究了酒色着色菌(Chromatiumvinosum DSM185)利用产酸克雷伯氏菌(Klebsiellaoxytoca HP1)发酵产氢废液进行光发酵和暗发酵产氢的可行性,以达到对产氢底物的充分利用和对产氢废液的进一步处理。研究结果表明C.vinosum可以利用K.oxytoca的发酵废液进行光发酵产氢和暗发酵产氢。C.vinosum发酵产氢后废液中残余还原糖和主要有机酸(丁酸)的含量明显降低,发酵产氢的最佳pH为6.5,添加0.1%(W/W)NH4Cl能促进产氢。在光照条件下丁酸利用率可达54.38%,产氢量达36.97mL/mg;在黑暗条件下丁酸利用率可达36.01%,产氢量达37.50mL/mg。     

利用电化学活跃微生物协助电解发酵产氢

摘要：电解协助发酵产氢是在外源电解协助下,利用电化学活跃微生物在石墨阳极上生长达到彻底氧化因发酵产氢残存的有机酸,产生CO2、电子与质子,电子进入石墨阳极经导线传到铂阴极,而质子则穿过阳离子膜进入阴极池,在无氧环境下,通过外加电压和铂的催化下,电子与质子结合为氢。此过程电子回收率可达90%以上,产氢效率可达8-9mol H2/mol Glucose。这一战略从根本上克服发酵产氢的发酵障碍和代谢产物的反馈抑制,极大地提高了氢转化率,极有可能率先应用于能源作物原料的氢能转化、以及有机污水和有机废弃物处理。     

Effect of initial bacteria concentration on hydrogen gas production from cheese whey powder solution by thermophilic dark fermentation

Dark fermentative hydrogen gas production from cheese whey powder solution was realized at 55°C. Experiments were performed at different initial biomass concentrations varying between 0.48 and 2.86 g L^?1 with a constant initial substrate concentration of 26 ± 2 g total sugar (TS) per liter. The highest cumulative hydrogen evolution (633 mL, 30°C), hydrogen yield (1.56 mol H₂ mol^?1 glucose), and H₂ formation rate (3.45 mL h^?1) were obtained with 1.92 g L^?1 biomass concentration. The specific H₂ production rate decreased with increasing biomasss concentration from the highest value (47.7 mL g^?1 h^?1) at 0.48 g L^?1 biomass concentration. Total volatile fatty acid concentration varied beetween 10 and 14 g L^?1 with the highest level of 14.2 g L^?1 at biomass concentration of 0.48 g L^?1 and initial TS content of 28.4 g L^?1. The experimental data were correlated with the Gompertz equation and the constants were determined. The most suitable initial biomass to substrate ratio yielding the highest H₂ yield and formation rate was 0.082 g biomass per gram of TS. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 28: 931–936, 2012     

Changes in bacterial community during fermentative hydrogen and acid production from organic waste by thermophilic anaerobic microflora

AIMS: Changes in fermentation pattern during the treatment of organic wastes containing solid materials by thermophilic anaerobic microflora were investigated with respect to product formation and bacterial community structure during hydrogen production. METHODS AND RESULTS: Anaerobic microflora enriched from sludge compost was cultivated using artificial garbage slurry in a continuous flow-stirred tank reactor. Product formation varied depending on pH and hydraulic retention time (HRT) applied. Community analysis by terminal restriction fragment length polymorphism and clone library analysis of polymerase chain reaction-amplified bacterial 16S rDNA indicated that difference in the fermentative product distribution could be caused by different populations of micro-organisms in the microflora. CONCLUSION: Hydrogen fermentation with acetate/butyrate formation was optimized at <1.0 d HRT at pH 5.0 and 6.0. Thermoanaerobacterium thermosaccharolyticum was the dominant hydrogen-producing micro-organism. Conversely, unidentified organisms became dominant after 4.0 d HRT at pH 7.0 and 8.0, where relatively high-solubilization efficiency of solid materials was observed with no production of hydrogen. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report describing product formation in the fermentation of solid organic wastes by a mixed population of micro-organisms. Various fermentation patterns including hydrogen fermentation were characterized and evaluated from engineering and microbial aspects.     

Effects of different pretreatment strategies on corn stalk acidogenic fermentation using a microbial consortium

The effects of sulfuric acid, acetic acid, aqueous ammonia, sodium hydroxide, and steam explosion pretreatments of corn stalk on organic acid production by a microbial consortium, MC1, were determined. Steam explosion resulted in a substrate that was most favorable for microbial growth and organic acid productions. The total amounts of organic acids produced by MC1 on steam exploded, sodium hydroxide, sulfuric acid, acetic acid, and aqueous ammonia pretreated corn stalk were 2.99, 2.74, 1.96, 1.45, and 2.21 g/l, respectively after 3 days of fermentation at 50 °C. The most prominent organic products during fermentation of steam-exploded corn stalks were formic (0.86 g/l), acetic (0.59 g/l), propanoic (0.27 g/l), butanoic (0.62 g/l), and lactic acid (0.64 g/l) after 3 days of fermentation; ethanol (0.18 g/l), ethanediol (0.68 g/l), and glycerin (3.06 g/l) were also produced. These compounds would be suitable substrates for conversion to methane by anaerobic digestion.     

Microbial production of specialty organic acids from renewable and waste materials

Microbial production of organic acids has become a fast-moving field due to the increasing role of these compounds as platform chemicals. In recent years, the portfolio of specialty fermentation-derived carboxylic acids has increased considerably, including the production of glyceric, glucaric, succinic, butyric, xylonic, fumaric, malic, itaconic, lactobionic, propionic and adipic acid through innovative fermentation strategies. This review summarizes recent trends in the use of novel microbial platforms as well as renewable and waste materials for efficient and cost-effective bio-based production of emerging high-value organic acids. Advances in the development of robust and efficient microbial bioprocesses for producing carboxylic acids from low-cost feedstocks are also discussed. The industrial market scenario is also reviewed, including the latest information on the stage of development for producing these emerging bio-products via large-scale fermentation.     

不同稻蟹生产模式对土壤活性有机碳和酶活性的影响

采取田间定位试验与室内分析相结合的方法,研究了有机稻蟹、常规稻蟹与单作水稻生产模式对土壤活性有机碳和酶活性的影响。结果表明,与单作水稻模式相比,有机稻蟹模式下的土壤总有机碳(TOC)、活性有机碳(LOC)、中活性有机碳(MLOC)、高活性有机碳(HLOC)含量及碳库管理指数(CMI)均显著或者极显著提高,且有机肥用量越大,效果越显著;有机稻蟹模式显著提高了土壤过氧化氢酶、脲酶、转化酶及碱性磷酸酶活性,与2009年相比,2010年中量有机肥稻蟹模式(M3)的LOC和MLOC含量增幅最高,分别达10.11%和5.14%;低量有机肥稻蟹模式(M4)的脲酶和碱性磷酸酶活性增幅最为明显,分别达80.25%和46.62%;常规稻蟹模式各指标的变化也有其类似的规律,但均明显低于有机稻蟹模式。相关分析表明,TOC、LOC、MLOC与4种土壤酶活性呈显著或者极显著正相关,相关系数最低为0.584*(P<0.05),最高可达0.940**(P<0.01)。因此,有机稻蟹生产模式不仅能显著提高土壤有机质的数量和质量,而且能增加土壤酶活性,提高土壤肥力。     

Influence of initial pH on hydrogen production from cheese whey

Batch experiments were conducted to investigate the effect of initial pH, between 5 and 10, on fermentative hydrogen production from crude cheese whey (87.5% (v/v) by Clostridium saccharoperbutylacetonicum). Hydrogen was produced over the range of pH studied. The hydrogen production rate and yield peaked at an initial pH 6 and then steadily decreased as the pH increased. The highest rate and yield were 28.3 ml h⁻¹ and 7.89 mmol g⁻¹ lactose, respectively. Sugar consumption was unaffected between pH 5 and 9 and remained at 97%. All final pHs were acidic and increased alongside the initial pH. There was no correlation between the initial pH and the fermentation time; the times were shorter (50–52 h) between pH 6 and 8, and longer (62–82 h) outside this range. A modified Gompertz equation adequately described fermentative hydrogen production from cheese whey. The respective maximum hydrogen production rate and hydrogen potential at an optimal pH of 6 were 47.07 ml h⁻¹ and 1432 ml. Lag phase times were much longer at acidic pHs than at alkaline pHs.     

Thermodynamic prediction of hydrogen production from mixed-acid fermentations

The MixAlco? process biologically converts biomass to carboxylate salts that may be chemically converted to a wide variety of chemicals and fuels. The process utilizes lignocellulosic biomass as feedstock (e.g., municipal solid waste, sewage sludge, and agricultural residues), creating an economic basis for sustainable biofuels. This study provides a thermodynamic analysis of hydrogen yield from mixed-acid fermentations from two feedstocks: paper and bagasse. During batch fermentations, hydrogen production, acid production, and sugar digestion were analyzed to determine the energy selectivity of each system. To predict hydrogen production during continuous operation, this energy selectivity was then applied to countercurrent fermentations of the same systems. The analysis successfully predicted hydrogen production from the paper fermentation to within 11% and the bagasse fermentation to within 21% of the actual production. The analysis was able to faithfully represent hydrogen production and represents a step forward in understanding and predicting hydrogen production from mixed-acid fermentations.     

Effect of initial pH independent of operational pH on hydrogen fermentation of food waste

The effect of initial pH from 5.0 to 9.0 on H₂ fermentation of food waste was investigated. In this batch experiment, however, unlike previous studies for initial pH, operational pH was maintained at 5.0 by the addition of alkaline solution. Although the period for pH drop from the initial values to 5.0 was less than one-tenth of the entire fermentation, this short period significantly affected the H₂ production performance. At initial pH 6.0-9.0, successful H₂ yield of 1.3-1.9 mol H₂/mol hexose_added was achieved with a peak value at pH 8.0. The H₂ yield achieved at initial pH 8.0 was corresponded to the 8.13% of total energy content in the substrate. At initial pH 5.0, the smallest butyrate production, but the highest ethanol production was detected, indicating unfavorable conditions for H₂ production. There was no significant relationship between total required amount of alkaline solution and initial pH values.     

Enhancement of bioenergy production from organic wastes by two-stage anaerobic hydrogen and methane production process

The present study investigated a two-stage anaerobic hydrogen and methane process for increasing bioenergy production from organic wastes. A two-stage process with hydraulic retention time (HRT) 3 d for hydrogen reactor and 12 d for methane reactor, obtained 11% higher energy compared to a single-stage methanogenic process (HRT 15 d) under organic loading rate (OLR) 3 gVS/(L d). The two-stage process was still stable when the OLR was increased to 4.5 gVS/(L d), while the single-stage process failed. The study further revealed that by changing the HRT_hydrogen:HRT_methane ratio of the two-stage process from 3:12 to 1:14, 6.7%, more energy could be obtained. Microbial community analysis indicated that the dominant bacterial species were different in the hydrogen reactors (Thermoanaerobacterium thermosaccharolyticum-like species) and methane reactors (Clostridiumthermocellum-like species). The changes of substrates and HRT did not change the dominant species. The archaeal community structures in methane reactors were similar both in single- and two- stage reactors, with acetoclastic methanogens Methanosarcina acetivorans-like organisms as the dominant species.     

Effects of pH and hydraulic retention time on hydrogen production versus methanogenesis during anaerobic fermentation of organic household solid waste under extreme-thermophilic temperature (70 degrees C)

Two continuously stirred tank reactors were operated with household solid waste at 70 degrees C, for hydrogen and methane production. The individual effect of hydraulic retention time (HRT as 1, 2, 3, 4, and 6 days) at pH 7 or pH (5, 5.5, 6, 6.5, 7) at 3-day HRT was investigated on the hydrogen production versus methanogenesis. It was found that at pH 7, the maximum hydrogen yield was 107 mL-H(2)/g VS(added) (volatile solid added) but no stable hydrogen production was obtained as after some time methanogenesis was initiated at all tested HRTs. This demonstrated that sludge retention time alone was not enough for washing out the methanogens at pH 7 under extreme-thermophilic conditions. Oppositely, we showed that keeping the pH level at 5.5 was enough to inhibit methane and produce hydrogen stably at 3-day HRT. However, the maximum stable hydrogen yield was low at 21 mL-H(2)/g VS(added).