S-TE预处理污泥厌氧发酵产氢

应用嗜热酶污泥溶解(S-TE)技术预处理剩余污泥,研究接种外在产氢菌(Enterococcus sp.LG1)和未接种外在产氢菌两种状况下,污泥发酵的产氢效果,并与相应温度(65℃)热预处理污泥的发酵产氢效果进行对比,分析探讨了污泥发酵产氢过程中底物和pH值的变化。结果表明:经S-TE预处理的污泥在未接种外在产氢菌时,产氢效果良好,最大产氢率(H_2/VS)高达16.3mL H_2/g,高出65℃热预处理污泥接种产氢菌15.6%,高出65℃热预处理污泥未接种产氢菌26.4%,发酵气体中只含有H_2和CO_2,不含CH_4,氢延迟时间短(3～4h),产氢率达最大值后能较稳定维持10h以上;S-TE预处理污泥接种产氢菌后,产氢效果不佳,最大产氢率仅为10.7mL/g。S-TE预处理污泥发酵过程中,可溶性蛋白质和可溶性糖是产氢发酵的主要营养物质。     

厨余和污泥不同混合比例碱处理产氢特性研究

以厨余垃圾和污泥为反应底物,加热预处理的污泥为发酵接种物,考察了碱处理下厨余与污泥不同混合比例的发酵产氢特性。结果表明:不同pH碱液对厨余垃圾进行预处理后,其效果以pH=13时最佳,预处理3h后SCOD和还原糖含量分别为31316.8mg/L和5.54mg/mL;碱预处理后的污泥与厨余联合发酵能够改善物料的营养平衡,缩短反应延迟时间到1h内;当厨余与污泥混和比例为5:1时为本试验最佳的试验条件,其氢气含量、比产氢速率峰值和氢产率分别为52.69%,1.73mL H_2/(h·gVS)和50.27mL H_2/gVS。     

厨余与污泥联合发酵不同预处理产氢特性研究

以厨余垃圾和污泥为反应底物,加热预处理的污泥为发酵接种物,考察了对反应底物进行碱、酸和热3种预处理的发酵产氢特性.试验结果表明:经过预处理的反应底物中的可溶性营养物质(SCOD和还原糖)总量有明显增长;预处理后发酵所产氢气含量、比产氢速率和氢产率都有较大改善,其中以加热预处理提高效果最为明显,最大氢气含量、最大比产氢速率(VS)和最高氢产率(VS)为47.68%,2.89 ml/(h·g)和57.74 ml/g,相对于未经过预处理的发酵样品分别提高了0.89倍,5.14倍和3.16倍.     

丁酸型产氢细菌WN9利用谷糠发酵的产氢特征

该研究从牡丹江江滨公园的河道底泥样中筛选获得1株丁酸型发酵产氢细菌的新菌株Clostridium butyricum WN9,并分别以葡萄糖和小米内、外壳谷糠为底物进行发酵产氢实验。实验结果表明:以葡萄糖为底物时,最大比产氢率为1.89 mol/mol;以小米内、外壳谷糠为底物时,内壳谷糠更易被利用,最适宜的内、外壳谷糠浓度分别为50,30 g/L,最大比产氢率分别为20.1,12.7 mL/g;低初始pH值条件(pH6.0)有利于提高谷糠转化效率,当内、外壳谷糠浓度均为50 g/L,初始pH值为6.0时,最大比产氢率分别提高至21.5,15.5 mL/g。     

玉米秸秆酶解与厌氧发酵产氢实验研究

以粒度小于0.088 mm秸秆粉的酶解液为底物与热预处理活性污泥(其中TS%为6.77%,VS%为47.90%,COD为36.665 g/L)进行厌氧发酵产氢实验,以累积产氢量和产氢速率为考察指标,研究不同热预处理(100℃水浴)时间、初始p H值、酶解液浓度、发酵温度对厌氧发酵产氢的影响,并利用修正的Gompertz方程对产氢过程进行回归分析,优化出最佳玉米秸秆酶解液厌氧发酵产氢的工艺参数。结果表明:活性污泥利用玉米秸秆酶解液进行厌氧发酵产氢时,当活性污泥热预处理时间为15 min、初始p H值为5.0、玉米秸秆粉酶解液浓度为22.34 mg/m L、发酵温度为40℃时,产氢效果最佳,此时最大累积产氢量达到653.98 m L,最大产氢速率为15.89 m L/h。     

预处理方法对活性污泥利用木糖产氢的影响

以木质纤维素水解后的主要单糖——木糖为底物,研究了酸处理、碱处理、热处理、红外照射处理活性污泥对发酵产氢过程中的产氢量、产氢速率、产氢延迟时间的影响。实验结果表明:在100℃的条件下,最佳热处理时间为10min,在该条件下,80ml培养基累计产氢量和每小时最大产氢速率分别达到312ml和22ml/h,较未处理的活性污泥分别提高133%和50%;最佳的酸处理条件为pH=4,处理活性污泥24h,可使产氢的延迟期由10h缩短为2h,累计产氢量和产氢速率分别提高58.2%和42.5%;红外处理和碱处理对产氢的延迟期没有影响,对累计产氢量和产氢速率的影响也相对较弱。     

磷酸盐浓度对产氢细菌Ethanoligenens harbinense YUAN-3生长和产气的影响

以产氧发酵细菌YUAN-3(Ethanoligenens harbinense)为研究对象,通过间歇产氢实验,考察磷酸盐的浓度对YUAN-3生长和产气的影响.研究结果表明在磷酸盐浓度小于15mmol/L时,生物量较高,细胞干重大于0.4g/L;整个发酵过程的平均产氢速率和比产氢率在磷酸盐浓度为8mmol/L时达到最大,为5.92mmol/g-干细胞·h和2.86molH2/mol-葡萄糖.     

玉米秸秆破碎度与酶解光合制氢的关系研究

以玉米秸秆为原料,利用微化破碎和酶水解结合的预处理方法,采用自制的光合制氢实验装置,进行不同破碎度对酶解光合制氢过程的影响实验研究,结果表明:当玉米秸秆破碎度为53~61μm时,最大比产氢速率约为26.4mL/(L·h),光能转化率达到25%,底物能量转化率约为5.3%,既具有较高的累计产氢量,又保证了较好的光能转化率和底物能量转化率,产氢综合效果最好。     

光合产氢细菌优势菌群富集及其产氢实验研究

利用特殊培养基从光照充裕、有机质含量高的猪场粪便排放处的污泥中富集培养光合细菌混合产氢菌群,对该混合菌群的产氢培养基进行优化,并研究混合菌群的产氢特性。实验结果表明,此菌群的最佳产氢培养基配方为:氯化铵0.4g/L,氯化镁0.2g/L,酵母膏0.1g/L,磷酸氢二钾0.5g/L,氯化钠2.0g/L,谷氨酸钠3.5g/L。此菌群以1%的葡萄糖为基质时,产氢时间长达204h,最大产氢量为3.41L/L,最大产氢速率为44.17mL/(L.h),最高氢气含量为46.73%,具有工业化应用价值。     

诱变育种选育高效产氢细菌

从自行研制的CSTR反应器中分离出一株产氢发酵细菌Ethanoligenens sp.ZGX4,以其为出发菌株,进行紫外和亚硝酸复合诱变选育,经过连续传代得到一株遗传稳定性很好的高效产氢突变株YR-3。在培养条件分别为36±1℃,初始pH为6.0,葡萄糖浓度为12g/L,其单位体积产氢量(Y_H_2)为3097.5mL/Lculture,产氢能力比对照提高70.5%,最大产氢速率为36.6mmol/g·drycell·h,比对照高出55.1%;发酵液相末端产物是以乙醇和乙酸为主的典型乙醇型发酵代谢类型。高效产氢耐酸突变体YR-3的释氢能力和产氢速率明显高于野生菌株ZGX4,显示了较强的商业应用潜力,也可为以后进一步探讨研究乙醇型细菌的制氢机制及代谢途径提供物质材料。     

Enriching hydrogen-producing bacteria from digested sludge by different pretreatment methods

The pretreatment of digested sludge by different methods, including ionizing irradiation, heat-shock, acid and base, was performed for enriching hydrogen-producing bacteria. These methods were evaluated and compared based on their suitability in the enrichment of hydrogen-producing bacteria in dark fermentation with glucose as a substrate in batch tests. The experimental results showed that the seed sludge pretreated by ionizing irradiation achieved the best hydrogen production among the different pretreatment methods, and the maximum hydrogen production potential, maximum hydrogen production rate, hydrogen yield and substrate degradation rate were 525.6 mL, 37.2 mL/h, 267.7 mL/g glucose (2.15 mol/mol glucose) and 98.9%, respectively. Ionizing irradiation can be a good optional pretreatment method for enriching hydrogen-producing bacteria from digested sludge. The effect of ionizing irradiation on the microbial community structure dynamics of the pretreated sludge deserves further study, which will help us to understand the mechanisms leading to the effect of high bio-hydrogen production.     

The effect of heat pretreatment temperature on fermentative hydrogen production using mixed cultures

The effect of heat treatment at different temperatures on two types of inocula, activated sludge and anaerobically digested sludge, was investigated in batch cultures. Heat treatments were conducted at 65, 80 and 95 °C for 30 min. The untreated inocula produced less amount of hydrogen than the pretreated inocula, with lactic acid as the main metabolite. The maximum yields of 2.3 and 1.6 mol H₂/mol glucose were achieved for the 65 °C pretreated anaerobically digested and activated sludges, respectively. Approximately a 15% decrease in yield was observed with increasing pretreatment temperature from 65 to 95 °C concomitant with an increase in butyrate/acetate ratio from 1.5 to 2.4 for anaerobically digested sludge. The increase of pretreatment temperature of activated sludge to 95 °C suppressed the hydrogen production by lactic acid fermentation. DNA analysis of the microbial community showed that the elevated pretreatment temperatures reduced the species diversity.     

Gamma irradiation as a pretreatment method for enriching hydrogen-producing bacteria from digested sludge

Gamma irradiation was used as a pretreatment method for enriching hydrogen-producing bacteria from digested sludge. The experimental results demonstrated that 5.0 kGy was optimal dose among the different doses (0.5–10 kGy) applied in this study. The maximum cumulative hydrogen production, hydrogen yield, hydrogen production rate and substrate degradation efficiency of the sludge irradiated at such dose were 529.4 mL, 267.7 mL/g glucose, 37.25 mL/h and 98.9%, respectively when the fermentation conditions were as follows: at 36 °C, initial pH 7.0 and 10 g/L glucose as substrate. In comparison with the conventional pretreatment methods, such as heat-shock, acid, base, aeration and chloroform, gamma irradiation was more powerful pretreatment method for enriching hydrogen-producing bacteria. The effect of Gamma irradiation on the microbial community structure of the pretreated sludge needs further study.     

Enrichment of the hydrogen-producing microbial community from marine intertidal sludge by different pretreatment methods

To determine the effects of pretreatment on hydrogen production and the hydrogen-producing microbial community, we treated the sludge from the intertidal zone of a bathing beach in Tianjin with four different pretreatment methods, including acid treatment, heat-shock, base treatment as well as freezing and thawing. The results showed that acid pretreatment significantly promoted the hydrogen production by sludge and provided the highest efficiency of hydrogen production among the four methods. The efficiency of the hydrogen production of the acid-pretreated sludge was 0.86 ± 0.07 mol H₂/mol glucose (mean ± S.E.), whereas that of the sludge treated with heat-shock, freezing and thawing, base method and control was 0.41 ± 0.03 mol H₂/mol glucose, 0.17 ± 0.01 mol H₂/mol glucose, 0.11 ± 0.01 mol H₂/mol glucose and 0.20 ± 0.04 mol H₂/mol glucose, respectively. The result of denaturing gradient gel electrophoresis (DGGE) showed that pretreatment methods altered the composition of the microbial community that accounts for hydrogen production. Acid and heat pretreatments were favorable to enrich the dominant hydrogen-producing bacterium, i.e. Clostridium sp., Enterococcus sp. and Bacillus sp.. However, besides hydrogen-producing bacteria, much non-hydrogen-producing Lactobacillus sp. was also found in the sludge pretreated with base, freezing and thawing methods. Therefore, based on our results, we concluded that, among the four pretreatment methods using acid, heat-shock, base or freezing and thawing, acid pretreatment was the most effective method for promoting hydrogen production of microbial community.     

Evaluation of different pretreatment methods for preparing hydrogen-producing seed inocula from waste activated sludge

Waste activated sludge (WAS) is the most favorable inoculum for dark fermentative hydrogen-producing processes, because it can be collected economically. In order to accelerate the start-up process and develop the efficiency and stability of a hydrogen production system, pretreatment of the seed sludge has been examined to enrich hydrogen-producing bacteria. Six pretreatment methods including acid, base, heat-shock, aeration, chloroform and 2-bromoethanesulfonate (BES) were performed on WAS in batch cultures utilizing glucose as the substrate. The results showed that, at 35 °C and initial pH of 7.0, hydrogen yields of the pretreated sludge (except for BES) were higher than the control test. The pretreatment methods resulted in different distributions of soluble metabolites. Acid pretreatment at pH of 3 was the best among all six pretreatment methods, and the maximal hydrogen yield of 1.51 mol/mol-glucose-consumed and the maximal specific hydrogen production of 22.81 mmolH₂/g VSS were observed. The hydrogen yield of the acid treated sludge increased to 1.82 mol/mol-glucose-consumed after five repeated-batch cultivations. It was concluded that acid pretreatment is a simple, economic and effective method for enriching hydrogen-producing bacteria from WAS.     

生物制氢反应器产氢产乙酸菌群对挥发酸的转化

采用间歇培养的方式,利用取自生物制氢反应器的厌氧活性污泥考察了活性污泥中产氢产乙酸菌群对乙醇、乙酸、丙酸、丁酸、戊酸和乳酸的转化和产氢。结果表明,培养时间为44h时,厌氧活性污泥发酵葡萄糖的累计产气量为356mL,累计产氢量为209mL,氢气含量为58.7%。发酵产物的组成成分乙醇为427.1mg/L、乙酸为716.5mg/L、丙酸为172.5mg/L、丁酸为689.4mg/L、戊酸为123.6mg/L。发酵生物制氢反应器厌氧活性污泥中产氢产乙酸菌群能够对乙醇和乳酸进行产氢产乙酸转化,厌氧污泥转化乙醇形成的乙酸含量约为270mg/L,累计产氢量为15mL;转化乳酸形成的乙酸含量约为190mg/L,累计产氢量为7mL。厌氧污泥不能对乙酸、丙酸、丁酸和戊酸进行产氢产乙酸转化,培养过程中也没有气体生成,分析认为产氢产乙酸菌群对挥发酸的转化不是发酵生物制氢反应器产氢的主要途径。     

Influence of thermal and chemical pretreatment on structural stability of granular sludge for high-rate hydrogen production in an UASB bioreactor

Fermentation of organic waste materials presents an alternate route instead of photosynthetic and chemical routes for hydrogen production. Low yield of biohydrogen production is the major challenge in the fermentative hydrogen-producing technology. Improvement of fermentation process by various sludge pretreatment methods is one of the ways that have been applied to boost hydrogen productivity. This study sheds new light on the impact of thermal and chemical pretreatments on the hydrogen-producing granular sludge morphology and strength as well as up-flow anaerobic sludge blanket (UASB) reactor performance treating palm oil mill effluent (POME). Thermal pretreatment showed devastating effects on the morphological and structural characteristics of the granules. However, the chemically pretreated granules remained structurally stable and relatively undamaged. The thermal pretreatment increased the cumulative hydrogen production by 40% and 76% over chemical pretreatment and control test (untreated), respectively.     

Comparison of different pretreatment methods for hydrogen production using environmental microbial consortia on residual glycerol from biodiesel

The pretreatment of environmental microbial consortia by five methods (acid, base, heat shock, dry heat and desiccation, freezing and thawing) was conducted in order to evaluate their applicability for the selection of hydrogen-producing bacteria capable of using residual glycerol from biodiesel synthesis as substrate. Results showed that substrate degradation rates of consortia pretreated with dry heat and desiccation and heat shock were higher compared with controls during the fermentation using glycerol, with degradation rates as high as 65%. The maximal hydrogen and biomass productions were obtained by dry heat and desiccation: 34.19% mol and 4340 mg/L, respectively. Dry heat and desiccation followed by heat shock are simple pretreatments methods that can be used to improve the biotechnological production of hydrogen. DNA sequencing performed to identify the bacteria strains present in the consortium showed that they belonged to the genus Klebsiella and Pantoea.     

Enhanced hydrogen production in a UASB reactor by retaining microbial consortium onto carbon nanotubes (CNTs)

Biohydrogen and subsequent biomethane generation from biomass is a promising strategy for renewable energy supply, because this combination can lead to higher energy recovery efficiency and faster fermentation than single methane fermentation. Microbial consortium control by retaining hydrogen-producers through the addition of microbial carriers is an alternative to constructing hydrogen-producing reactors. Here we report the use of carbon nanotubes (CNTs) as microbial carriers to enhance microbial retention and the production of biohydrogen. Laboratory-scale upflow anaerobic sludge blanket (UASB) reactors with CNTs at 100 mg/L achieved a maximal hydrogen production rate of 5.55 L/L/d and a maximal hydrogen yield of 2.45 mol/mol glucose. Compared to frequently used activated carbon (AC) particles, CNTs resulted in quicker startup and better performance of hydrogen fermentation in UASB reactors. Scanning electron microscopy (SEM) and pyrosequencing results revealed that the reactor with CNTs led to a high proportion of hydrogen-producing bacteria among the microbial consortium, which endowed the microbes with strong flocculation capacity and hydrogen productivity.     

Effect of heat pre-treatment temperature on isolation of hydrogen producing functional consortium from soil

A functional hydrogen producing consortium was isolated from soil by heat pre-treatment technique and hydrogen production at different substrate concentration was evaluated. The forest soil was heat pre-treated at 65, 80, 95, 105 and 120 °C temperature for 1 h. As revealed by PCR-DGGE analysis and hydrogen yield, the hydrogen producing microbial community changed with increase in heat pre-treatment temperatures giving potential hydrogen producing consortium at 95–105 °C soil pre-treatment. The maximum hydrogen production rate, hydrogen yield and cumulative hydrogen with 15–20 g glucose were 1390–1576 mL/L/day, 1.83–1.93 mol H₂/mol glucose, and 2966–3146 mL H₂/L, respectively. The metabolic pathways shifted from ethanol-type to acetate–formate type as soil pre-treatment temperature increased from 65 to 120 °C. The soil heat pre-treatment approach is effective for isolating hydrogen producing natural Clostridium consortium from the soil as enumerations of the functional strains need specific temperature range to florish.