Phototrophic hydrogen production from glucose by pure and co-cultures of Clostridium butyricum and Rhodobacter sphaeroides

Phototrophic hydrogen production from glucose by pure and co-cultures of Clostridium butyricum and Rhodobacter sphaeroides was studied in batch experiments. Results showed that in all batches hydrogen was produced after a lag phase of about 10 h; pure culture of R. sphaeroides produced hydrogen at rates substantially lower than C. butyricum. In co-culture systems, R. sphaeroides even with cell populations 5.9 times higher still could not compete with C. butyricum for glucose. In co-culture systems, R. sphaeroides syntrophically interacted with C. butyricum, using the acetate and butyrate produced by the latter as substrate for hydrogen production. Hydrogen production was ceased in all batches when the pH was lowered to the level of pH 6.5, resulting from the accumulation of fatty acids. It was also demonstrated in this study that fluorescence in situ hybridization (FISH) was an effective means for the quantification of the relative abundance of individual bacteria in a co-culture system.     

Efficient hydrogen production from acetate through isolated Rhodobacter sphaeroides

Photosynthetic bacteria produce hydrogen from lactate and acetate that are products of hydrogen producing bacteria in the dark. Thus, their coculture is a promising method for hydrogen production. However, the hydrogen production yield from acetate of Rhodobacter sphaeroides RV, which has been shown to possess the highest yield and hydrogen production rate, is low as compared to that from lactate. Photosynthetic bacteria that produce hydrogen from acetate as well as lactate were screened from lakes and swamps in the Tokyo and Chiba areas in Japan. Seventy-six strains of photosynthetic bacteria were obtained and the analysis of their 16S rRNA gene sequences revealed that they belong to R. sphaeroides. Among the isolated bacteria, R. sphaeroides HJ produced the highest amount of hydrogen from acetate and lactate. The HJ strain produced a 2300 ± 93 ml/L-broth of hydrogen from 75 mM acetate consumed during for 120 h of fermentation. The amount of hydrogen and the yield from acetate were 1.9 and 2.1 times higher, respectively, than those of R. sphaeroides RV. The amount and yield of hydrogen, produced by R. sphaeroides HJ from lactate were similar to those produced by R. sphaeroides RV. Since the amount and yield of produced hydrogen by the HJ strain were similar regardless of the substrate (acetate or lactate), its metabolic pathway could have a key to increasing hydrogen production from acetate.     

葛仙米藻胆蛋白的体外消化特性

研究葛仙米藻胆蛋白在体外模拟胃液和肠液的消化产物性质,重点测定不同消化时间产物的可溶性蛋白质、游离氨基含量变化及其抗氧化作用,并利用HPLC法测定消化产物分子质量变化情况。结果表明：在胃液和肠液消化作用下蛋白质含量均呈现下降趋势,而游离氨基含量呈现上升趋势,消化产物较初始产物对ABTS+·和脂质过氧化具有更强的抑制作用,但对·OH的清除能力却有所下降;偏相关分析结果表明,与葛仙米藻胆蛋白消化产物的抗氧化作用紧密相关的是消化产物中的分子质量为6ku和0.2ku的肽类。     

葛仙米多糖的提取、分离与纯化技术研究

葛仙米中富含多糖，并且具有优异的生物和生理活性，本文对葛仙米多糖的提取、分离进行了初步的研究，以期获得性能优良的葛仙米多糖。葛仙米经破碎、脱色、去脂、提取、Sevage法沉淀蛋白质、酒精沉淀多糖、离心、得到粗多糖，最后，通过真空冷冻干燥得到白色的水溶性多糖和褐色的碱溶性多糖，经红外光谱证实：水溶性多糖和碱溶性多糖具有一般多糖的特征。水溶性多糖的最佳提取参数是：90℃，6h，1：90加水，水提取4次，其提取率是14．09％；碱溶性多糖的最佳提取参数是：1mol／L的NaOH溶液，提取6h，加1：25的碱液，提取4次，其提取率是5，70％。     

Effects of light source,intensity and lighting regime on bio-hydrogen production from ground wheat starch by combined dark and photo-fermentations

Combined dark and photo-fermentation of ground wheat starch was carried out by using different light sources, intensities and lighting regime. A mixture of heat treated anaerobic sludge and Rhodobacter sphaeroides-RV with a certain light/dark bacteria ratio was used in batch experiments. Tungsten, fluorescent, infrared (IR), tungsten + infrared, halogen lamps were used as light sources with a light intensity of 270 Wm⁻² along with sunlight. Halogen lamp was found to be the most suitable light source yielding the highest cumulative hydrogen formation (178 ml) and yield (218 ml g⁻¹ starch). Combined fermentations were performed at different light intensities (1–10 klux) using the halogen lamp in the second set of experiments. The optimum light intensity was found to be 10 klux (approx. 352 Wm⁻²) resulting in the highest cumulative hydrogen (111 ml) and hydrogen yield (139 ml H₂ g⁻¹ starch). Hydrogen formation was limited by the availability of light at low light intensities below 10 klux. Durations of dark/light cycles were changed to determine the most suitable lighting regime. Hydrogen gas formation increased with increasing cycle time and continuous lighting resulted in the highest cumulative hydrogen formation and hydrogen yield.     

Photo-fermentative hydrogen gas production from dark fermentation effluent of ground wheat solution: Effects of light source and light intensity

Dark fermentation effluent of wheat powder solution was subjected to light fermentation for bio-hydrogen production using different light sources and intensities. Tungsten, fluorescent, infrared (IR), halogen lamps were used as light sources with a light intensity of 270 Wm⁻² along with sunlight. Pure culture of Rhodobacter sphaeroides-RV was used in batch light fermentation experiments. Halogen lamp was found to be the most suitable light source yielding the highest cumulative hydrogen formation (CHF, 252 ml) and yield (781 ml H₂ g⁻¹ TVFA). In the second set of experiments, light fermentations were performed at different light intensities (1–10 klux) using halogen lamp. The optimum light intensity was found to be 5 klux (approx. 176 Wm⁻²) resulting in the highest CHF (88 ml) and hydrogen yield (1037 ml H₂ g⁻¹TVFA). Hydrogen formation was limited by the availability of light at low light intensities below 5 klux and was inhibited by the excess light above 5 klux.     

Bio-hydrogen production by photo-fermentation of dark fermentation effluent with intermittent feeding and effluent removal

Pure culture of Rhodobacter sphaeroides (NRRL- B1727) was used for continuous photo-fermentation of volatile fatty acids (VFA) present in the dark fermentation effluent of ground wheat starch. The feed contained 1950 ± 50 mg L⁻¹ total VFA with some nutrient supplementation. Hydraulic residence time (HRT) was varied between 24 and 120 hours. The highest steady-state daily hydrogen production (55 ml d⁻¹) and hydrogen yield (185 ml H₂ g⁻¹ VFA) were obtained at HRT = 72 hours (3 days). Biomass concentration increased with increasing HRT. Volumetric and specific hydrogen formation rates were also maximum at HRT = 72 h. High extent of TVFA fermentation at HRT = 72 h resulted in high hydrogen gas production.     

Effect of AI crude extract on PHB accumulation and hydrogen photoproduction in Rhodobacter sphaeroides

Poly-β-hydroxy butyric acid (PHB) accumulation and gaseous H₂ release are regarded as alternatives for expending reducing power. Some researchers suggested that quorum-sensing system affects PHB accumulation in Rhodobacter sphaeroides, but whether the system plays regulation role between hydrogen producing and PHB synthesis is still unknown. By adding autoinducer of R. sphaeroides into its culture solutions, measuring its total hydrogen production, PHB content and PHB synthase activity, the function of quorum-sensing on PHB accumulation and hydrogen production was preliminarily investigated. Compared with the control, the total gas productions in experimental groups increased accompanying slight decrease of PHB contents, which was partially caused by the reduction of PHB synthase activities. Biolog tests indicated the carbon source utilization profiles, especially those involving fatty acids and butanoate metabolism, had partly changed after exogenous signal molecules added. These results suggest that quorum-sensing is involved in signal regulation between PHB accumulation and hydrogen production in R. sphaeroides.