光合细菌小分子酸醇产氢试验研究

以光合产氢混合菌群为研究对象,研究了光合细菌在乙酸、乙醇、乳酸、丁酸几种小分子脂肪酸条件下菌体的生长和产氢特性,详细考察了乙酸和丁酸对光合产氢细菌生长和产氢的影响.研究发现,乙酸、丁酸既是光合细菌良好的生长碳源,也是高效氢供体,光合细菌在乙酸和丁酸条件下产氢率分别达到2.05和2.81molH2/mol.光合细菌以乙酸和丁酸产氢时,乙酸和丁酸的最佳添加浓度均为40mmol/L;光合细菌在乳酸条件下有较高的生长活性,但乳酸并不是光合细菌高效氢供体,光合细菌在乳酸条件下产氢活性较低;乙醇既不是光合细菌良好生长碳源,也不是高效氢供体,乙醇对光合细菌的生长和产氢均有较强的抑制作用.     

光合细菌混合菌群HAU-M1产氢动力学实验研究

研究光合细菌混合菌群以葡萄糖为底物,光合产氢过程中的生长和产氢动力学特性,分析混合菌群利用葡萄糖产氢过程中的基质降解规律及代谢产物的生成规律。研究结果表明:光合细菌混合菌群以葡萄糖为底物产氢时,150 mmol/L的葡萄糖添加量是最佳添加浓度,产氢过程存在代谢产酸的过程,产氢高峰期葡萄糖主要代谢产物为乙酸,此时产气速率大;产氢末期葡萄糖主要代谢产物为丁酸,此时产气速率较低。建立基于Monod方程的光合细菌混合菌群产氢过程中的生长动力学模型,模型可较好地描述混合菌群产氢过程中生长延滞期和对数增长期菌体的生长变化规律,最大比生长速率μmax为0.214 h~(-1),饱和常数KS为8.257。建立光合细菌混合菌群产氢过程中的底物消耗动力学模型,模型可较好地描述混合菌群产氢过程中产氢延滞期和产氢高峰期的葡萄糖降解规律,细胞得率系数YX/S为0.352 g/mol,维持系数m为0.85。     

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。     

混合菌种利用淀粉在光照及黑暗条件下的产氢

进行了混合菌种利用淀粉进行光反应和暗反应的产氢对比试验.结果发现光合反应的产氢率以及产氢速率均高于暗反应,但产氢时间滞后于暗反应.对反应的菌液进行了DNA提取、纯化以及PCR扩增,通过对DGGE图谱分析,发现光反应和暗反应的样品条带在数量和亮度上都存在一定差异,暗反应条件下产氢的优势菌群要略多于光合反应的菌群.随着淀粉浓度的增加,光合反应和暗反应的产氢总量均增大,但产氢率降低,其中光合反应的降低尤为明显,从2g/L淀粉浓度时的9.8mmol H2/g淀粉降低到40g/L淀粉浓度时的3.3mmol H2/g淀粉,产氢率降低了66%,而暗反应产氢率降低了43%.光合反应的尾液中,丁酸含量最高,而暗反应的尾液中,乙酸含量最高.     

利用乙酸光合细菌产氢的研究

通过间歇批次实验研究了不同乙酸浓度对光合细菌产氢速度、底物转化率、能量回收率等方面的影响,同时对氮源浓度进行了优化。研究结果表明:最佳的乙酸浓度为40mmol/L,在此条件下最大产氢速度、底物转化率和能量转化率分别为1.17mL/L、1.09mol-H_2/mol acetate和27.3%。当乙酸浓度为40mmol/L时,最佳的氮源浓度为8～9mmol/L。     

固定化光合细菌利用低分子有机酸的产氢特性

通过固定化光合细菌对低分子有机酸进行了光合产氢的批式试验研究.利用修正的Gompertz方程进行产氢动力学分析,并且对产氢过程中pH变化、有机酸的氢转化率以及有机酸初始浓度对产氢的影响等进行了分析.结果表明固定化能提高产氢率,以海藻酸钠为固定化载体的产氢效果最佳.同时发现有机酸产氢存在最佳初始浓度,其中乳酸产氢的最佳初始浓度为0.049mol/L,对于乙酸、丙酸和丁酸这3种小分子羧酸,其最佳初始浓度的大小随着有机酸碳原子数的增加而减小,即乙酸(0.043mol/L)丙酸(0.029mol/L)丁酸(0.022mol/L).乙酸的最大氢转化率最高,达到65.3%.浓度对氢气含量没有影响,而对于乙酸、丙酸和丁酸,氢气含量随着有机酸碳原子数的增加而增大.     

海洋光合菌群利用乙酸产氢的实验研究

通过富集获得产氢海洋光合菌群,该菌群可以有效利用发酵产氢的关键副产物乙酸作为产氢碳源.温度、光照强度、起始pH和乙酸浓度都对该菌群产氢和生长有明显影响.当在30℃、4000lx光照和起始pH=8.0的条件下培养时,此光合菌群产氢量和底物转化效率较高.乙酸浓度对产氢影响巨大,低浓度乙酸的底物转化效率较高,但总产氢量不高;高浓度乙酸的底物转化效率不高,但总产氢量较高.此实验结果为海洋光合细菌与海洋发酵细菌偶联产氢提供科学参考.     

维生素B4对秸秆类生物质光发酵产氢的影响

以玉米秸秆类生物质为产氢原料,研究维生素B4对HAU-M1光合细菌生长和产氢过程的影响规律。结果表明,当维生素B4浓度为75 mg/L时,光合细菌生长情况最好,细菌干重最大值为0.934 g/L;维生素B4浓度为100 mg/L时,氢气累积产量达178 mL,比对照组显著提高了43.8%,对光合细菌产氢的促进效果最好;添加维生素B4对HAU-M1光合细菌发酵产氢过程的pH值影响显著,可减弱发酵液酸化,有利于光合细菌发酵产氢。显见,维生素B4对HAU-M1光合细菌生长及秸秆类生物质光合产氢具有明显的促进作用,可为进一步研究开发秸秆类生物质光合细菌发酵产氢工艺技术提供科学参考。     

无机盐添加物对光合细菌制氢性能影响的试验研究

以碳酸盐(Na_2CO_3和版NaHCO_3)和磷酸盐(Na_2HPO_4、K_2HPO_4、NaH_2PO_4和KH_2PO_4)等作为无机盐添加物,进行同一浓度的碳酸盐和磷酸盐以及不同浓度的KH_2PO_4对光合细菌制氢性能影响的试验研究。结果表明碳酸盐和磷酸盐添加物均能有效缓冲反应体系的酸碱度,但只有KH_2PO_4和NaH_2PO_4的添加能明显促进光合细菌发酵产氢。产氢动力学的结果也表明KH_2PO_4和NaH_2PO_4的添加提高了反应体系的最大产氢潜能和最大产氢速率,缩短了产氢延迟时间。适量浓度的KH_2PO_4能有效提高反应体系的抗酸碱冲击性,同时磷元素在光合细菌的生长过程中起到相当重要的作用,适量的KH_2PO_4能有效促进光合细菌的生长代谢,而过量的KH_2PO_4则会极大地抑制光合细菌的生长代谢。当KH_2PO_4的浓度为40 mmol/L时产氢效果最佳,氢气产量和比产氢率达到最大值,分别为(323.84±8.96)mL和(1.30±0.04)mol/mol。产氢动力学的分析结果表明适量浓度的KH_2PO_4能提高最大产氢潜能和最大产氢速率,缩短产氢延迟时间,当KH_2PO_4浓度为40 mmol/L时,最大产氢潜能和最大产氢速率最大,产氢延迟时间最短,分别为333.15 mL、6.60 mL/h和16.41 h。     

光合细菌生物膜制氢反应器的产氢特性

对光合细菌生物膜制氢反应器的产氢性能进行了实验研究,探讨了光照度、光谱和底物浓度对反应器产氢性能的影响.实验结果表明:光合细菌生物膜反应器内最适底物浓度为0.12mol/L,最佳光照度为5000 lx,过高或过低的底物浓度和光照度均对光合细菌产氢具有抑制作用;而光的波长对光合细菌产氢的最适底物浓度和最佳光照度均无影响.当底物浓度为0.12mol/L,光照度为5000 lx,波长为590 nm时,反应器的产氢率达到最高,为3.54mg/h.     

Biohydrogen production by isolated halotolerant photosynthetic bacteria using long-wavelength light-emitting diode (LW-LED)

Biohydrogen is expected as one of the alternative energy to fossil fuel. In this study, halotolerant photosynthetic hydrogen producing bacteria (ht-PHB) were isolated from a sediment of tideland, and hydrogen gas (H₂) production by isolated ht-PHB from mixed short-chain fatty acids (SFAs) using a long-wavelength light emitting diode (LW-LED) was investigated. The isolated ht-PHB grow on a culture containing three kinds of SFAs (lactic acid, acetic acid, butyric acid) and produced H₂ with their complete consumption at NaCl concentration in the 0–3% range in the light of tungsten lamp. The isolated ht-PHB was phylogenetically identified as Rhodobacter sp. KUPB1. The KUPB1 showed well growth and H₂ production even under LW-LED light irradiation, indicating that LW-LED is quite useful as an energy-saving light source for photosynthetic H₂ production.     

Photo-fermentative hydrogen production performance of a newly isolated Rubrivivax gelatinosus YP03 strain with acid tolerance

Screening and excavating new photosynthetic bacteria with excellent hydrogen production performance is extremely important for improving the photo-fermentative hydrogen production. A new photosynthetic bacterium YP03 was isolated and identified to be Rubrivivax gelatinosus by morphological characterization and phylogenetic analysis. The effects of several key factors on hydrogen production performance were carried out. The results indicated that YP03 strain showed a preference for the carbon sources, and 5375 ± 398 mL/L of maximum hydrogen yield was obtained using butyrate medium. Meanwhile, YP03 strain could use several nitrogen sources to produce hydrogen, and glutamic acid was the optimum nitrogen source for hydrogen produced. Furthermore, YP03 exhibited better hydrogen production performance at initial pH 7.0, reaction temperature 33 °C and light intensity 5000 lux, and the maximum hydrogen production rate was 108.3 ± 12.4 mL/(Lh), which was relatively high compared with the previous reports by R. gelatinosus. Especially, the proper pH for hydrogen production by YP03 ranged from weak acid to neutral (6.5–7.0) and it still could produce hydrogen at pH 5.5 showing the characteristic of acid tolerance. It suggested that YP03 is a potential candidate for the integration of dark- and photo-fermentative hydrogen production. These findings contribute to our understanding of YP03 strain and provide a prospective photosynthetic bacterium for efficient hydrogen production in future research.     

Bio-hydrogen production by mixed culture of photo- and dark-fermentation bacteria

Clostridium butyricum and Rhodopseudomonas faecalis RLD-53 were employed to produce hydrogen in mixed culture with glucose as sole substrate. Due to the great difference on growth rate and acid-resistant capacity between photo-fermentative bacteria and dark-fermentative bacteria, directly mixed culture of the two kinds of bacteria in different ratio was studied in this work. Hydrogen yield, volatile acids, pH and biomass in different periods were evaluated. Acetic acid and butyric acid produced by C. butyricum were dominant terminal fermentation products, and they were effective substrates for photo-fermentative bacteria. The cooperation was formed in a way like food chain. But compared to the production rate of volatile acids produced by C. butyricum, the utilization rate by photo-fermentative bacteria was far slower. The results demonstrated that the growth of photo-fermentative bacteria was limited when pH decreased sharply. The best ratio of C. butyricum to R. faecalis RLD-53 was 1:600. The maximum yield of hydrogen reached 122.4 ml-H₂/vessel and hydrogen production rate was 0.5 ml-H₂/ml-culture/day.     

Inhibitory effect of ethanol,acetic acid,propionic acid and butyric acid on fermentative hydrogen production

The inhibitory effect of added ethanol, acetic acid, propionic acid and butyric acid on fermentative hydrogen production by mixed cultures was investigated in batch tests using glucose as substrate. The experimental results showed that, at 35 °C and initial pH 7.0, during the fermentative hydrogen production, the substrate degradation efficiency, hydrogen production potential, hydrogen yield and hydrogen production rate all trended to decrease with increasing added ethanol, acetic acid, propionic acid and butyric acid concentration from 0 to 300 mmol/L. The inhibitory effect of added ethanol on fermentative hydrogen production was smaller than those of added acetic acid, propionic acid and butyric acid. The modified Han–Levenspiel model could describe the inhibitory effects of added ethanol, acetic acid, propionic acid and butyric acid on fermentative hydrogen production rate in this study successfully. The modified Logistic model could describe the progress of cumulative hydrogen production.     

A pneumatically agitated flat-panel photobioreactor with gas re-circulation: anaerobic photoheterotrophic cultivation of a purple non-sulfur bacterium

The application of hydrogen as a clean and efficient energy carrier in the near future becomes more and more evident. Within the process of photobiological hydrogen production, purple non-sulfur bacteria are an interesting subject of study because of their high hydrogen producing capacity. In a previous study, the used Rhodopseudomonas sp. had proven to efficiently produce hydrogen from acetic acid and light energy. We constructed a pneumatically agitated flat-panel photobioreactor as a model system for optimization of photoheterotrophic hydrogen production. Batch experiments and a chemostat experiment were performed to investigate the proper functioning of the new photobioreactor. During the first experiments, argon gas was sparged through the system for mixing and inhibition of growth was observed. Experimental results indicate that the stripping of carbon dioxide from the culture liquid caused this inhibition of growth. Possibly, the Rhodopseudomonas sp. used requires carbon dioxide during growth on a highly reduced substrate like acetate. Recirculating the gas prevented the carbon dioxide from being stripped from the system. In this mode of operation, growth was supported.     

A comparison of hydrogen production among three photosynthetic bacterial strains

The characteristics of hydrogen production from individual and mixed volatile fatty acids (VFAs) were compared among three photosynthetic bacterial strains, Rhodopseudomonas sp., Rhodopseudomonas palustirs W004 and Rubrivivax sp. Rhodopseudomonas sp. and R. palustirs W004 could convert both butyrate and acetate into hydrogen. Rubrivivax sp. could assimilate butyrate and acetate, but could not produce hydrogen from them when individual VFA was used as substrate. The highest hydrogen amount (2191.7 mL/L culture), COD reduction efficiency (85.3%) and H₂ yield (468.3 mL H₂/g COD) were achieved by Rhodopseudomonas sp. with butyrate as carbon source. All the three strains could produce hydrogen from mixed VFAs. Rhodopseudomonas sp. and R. palustirs W004 could digest the substrates completely. Hydrogen production from mixed VFAs by Rubrivivax sp. lasted for 3.7 days and only 38.8% of COD was reduced, for high pH value of the culture harmed hydrogen production.     

Effect of extrinsic lactic acid on fermentative hydrogen production

In this paper we report the effect of extrinsic lactic acid on hydrogen production from a starch-containing medium by a mixed culture. Study of the effect of addition of four metabolites, namely ethanol, lactic acid, butyric acid and acetic acid illustrated that lactic acid had a positive effect on both the maximum hydrogen production and hydrogen production rate. The addition of 10 mM lactic acid to a batch containing starch increased the hydrogen production rate and hydrogen production yield from 4.31 to 8.23 mL/h and 5.70 to 9.08 mmol H₂/g starch, respectively. This enhancement in hydrogen production rate and yield was associated with a shift from acetic acid and ethanol formation to formation of butyric acid as the predominant metabolite. The increase in hydrogen production yield was attributed to the increase in the available residual NADH for hydrogen production. When lactic acid was used as the sole carbon source, no significant hydrogen production was observed.     

Effect of pH and sulfate concentration on hydrogen production using anaerobic mixed microflora

The effects of varying sulfate concentrations with pH on continuous fermentative hydrogen production were studied using anaerobic mixed cultures growing on a glucose substrate in a chemostat reactor. The maximum hydrogen production rate was 2.8 L/day at pH 5.5 and sulfate concentration of 3000 mg/L. Hydrogen production and residual sulfate level decreased with increasing the pH from 5.5 to 6.2. The volatile fatty acids (VFAs) and ethanol fractions in the effluent were in the order of butyric acid (HBu) > acetic acid (HAc) > ethanol > propionic acid (HPr). Fluorescence In Situ Hybridization (FISH) analysis revealed the presence of hydrogen producing bacteria (HPB) under all pH ranges while sulfate reducing bacteria (SRB) were present at pH 5.8 and 6.2. The inhibition in hydrogen production by SRB at pH 6.2 diminished entirely by lowering to pH 5.5, at which activity of SRB is substantially suppressed.     

Biohydrogen production by a mixed photoheterotrophic culture obtained from a Winogradsky column prepared from the sediment of a southern Brazilian lagoon

The potential of a photoheterotrophic mixed culture isolated from a Winogradsky column prepared with the sediment of Lagoa da Conceição, a lagoon situated in Florianópolis – Brazil, was evaluated with respect to hydrogen production. Partial characterization of the mixed culture was carried out by spectrophotometric analysis of the whole cell pigment and molecular analysis by PCR/DGGE. Hydrogen production from acetate and butyrate as carbon source and sodium glutamate as nitrogen source was accomplished in batch culture conducted in 10 mL bottles, at 30 °C, for 10 days, under light intensity of 5.86 W/m². The results showed the presence of bacteriochlorophyll a and carotenoids in the mixed culture, both of which are pigments present in the photosystem of purple non-sulfur (PNS) bacteria. DGGE analysis revealed four distinct bands corresponding to different sequences of 16S rDNA, thus suggesting the presence of four prokaryotic species. Hydrogen production from acetate and butyrate was observed. Maximum hydrogen production (143.56 mL/L and 135.41 mL/L for acetate and butyrate, respectively) and hydrogen production rates (0.60 mL/L h and 0.56 mL/L h for acetate and butyrate, respectively) were similar for both substrates, but acetate was 24% more efficient than butyrate in terms of substrate conversion into hydrogen. The results of this study are very promising, since a selected culture able to grow and produce hydrogen from two substrates with similar productivity was obtained via a simple methodology.