Media For Hydrogen Production Research Articles

Biological treatment of organic waste polluting the environment and bio-hydrogen production

Thirty four local isolates of bio-hydrogen producing anaerobic bacteria were isolated from samples of solid waste of sewage plants from different regions using liquid and solid mineral salt medium at initial pH of 7 and incubated at 37 ºC for 72 hr. .The ability of isolates was tested to produce bio-hydrogen, using liquid production medium. Results indicate that the bio-hydrogen production in 25 isolates cannot be detected, while 9 isolates showed the ability to produce bio-hydrogen and that theAn-18 isolate showed the highest level of bio-hydrogen production(34 ppm) after 72 hr. of incubation at 37 ºC. Anaerobic isolates producing bio-hydrogen were identified based on morphological characteristics and some biochemical tests, results showed that 7isolates belong to the genus Actinomycessp.and only two isolates belong to the genus Clostridium sp., Then prepared the mixed culture from 7 isolates and subsequently was used as inoculums for hydrogen production medium. Inoculated the bioreactor containing the residues of agricultural and household by mixed culture (1 ml/ 50 ml medium) at initial pH of 7 and incubated at 37 ºC by using water bath for 20 days ,and subsequently was estimated the amount of hydrogen produced in every day. The results showed that hydrogen production was started from the second day (12 ppm) andreached its maximum production for the period from 14-17 days after the start of the experiment.

Microarray analysis of high light intensity stress on hydrogen production metabolism of Rhodobacter capsulatus

Biohydrogen obtained from purple non sulfur bacteria (PNSB) is an environmentally friendly alternative for hydrogen production. PNSB can be employed in large scale outdoor photobioreactors to produce hydrogen by photofermentation with sunlight as the light source. In external environmental conditions, however, bacteria can experience stress due to high light intensities, which can inhibit or slow down hydrogen production. Previous studies with other PNSB showed varying responses to light intensities (above 4000 lux), in some cases improving, and in others adversely affecting hydrogen production.In this study, Rhodobacter capsulatus, a PNSB species that produce hydrogen efficiently from dark fermenter effluents containing acetate, was used to investigate the effects of high light intensity stress on the hydrogen production metabolism at the gene expression level. A microarray analysis was carried out using a custom-design Affymetrix GeneChip TR_RCH2a520699F. R. capsulatus DSM1710 was grown under a cyclic illumination of 2000 and 7000 lux (12 h light/12 h dark) in a hydrogen production medium having 30 mM acetate and 2 mM glutamate, and was exposed to a high light intensity (10,000 lux) for 1 h in the middle of a light period. The results reveal that photosynthetic reaction center genes were down-regulated in order to protect the photosynthetic membrane from damage. On the other hand, the expression of nitrogenase and electron transport system genes were enhanced by high light intensity. These results show that a high light intensity stress drives R. capsulatus to direct gene expression towards hydrogen production, which supports the hypothesis that hydrogen production is a way for the disposal of excess reducing equivalents to maintain the internal redox balance.

Cloning and heterologous expression of chlorophyll a synthase in Rhodobacter sphaeroides

Rhodobacter sphaeroides is a purple non-sulfur bacterium which photoheterotrophically produces hydrogen from organic acids under anaerobic conditions. A gene coding for putative chlorophyll a synthase (chlG) from cyanobacterium Prochlorococcus marinus was amplified by nested polymerase chain reaction and cloned into an inducible-expression plasmid which was subsequently transferred to R. sphaeroides for heterologous expression. Induced expression of chlG in R. sphaeroides led to changes in light absorption spectrum within 400-700 nm. The hydrogen production capacity of the mutant strain was evaluated on hydrogen production medium with 15 mM malate and 2 mM glutamate. Hydrogen yield and productivity were increased by 13.6 and 22.6%, respectively, compared to the wild type strain. The results demonstrated the feasibility of genetic engineering to combine chlorophyll and bacteriochlorophyll biosynthetic pathways which utilize common intermediates. Heterologous expression of key enzymes from biosynthetic pathways of various pigments is proposed here as a general strategy to improve absorption spectra and yield of photosynthesis and hydrogen gas production in bacteria.

Bio-hydrogen production by Pseudomonas stutzeri KF532951

Hydrogen production by biological means is more advantageous as it utilizes renewable sources and produces very low or no carbondioxide. Since, lignocellulosic feedstocks are cheaper source, the present study was aimed to isolate Pseudomonas stutzeri from soil sample at country bricks chamber furnace. Final confirmation of the strain was done by 16S rRNA sequencing. The GC content was calculated. The isolated strain was inoculated in hydrogen production medium containing sugarcane bagasse replacing glucose. After the incubation period of 16 days, the gas collected was studied for hydrogen production through gas chromatography technique. According to sequencing and phylogenetic tree results, our isolate was found to be P. stutzeri KF532951 . The GC content of our strain was above 53%. Our strain could produce up to 3.4 mol H 2 /mol substrate by water displacement method. On the basis of the above results, it is concluded that our strain is able to produce hydrogen biologically.

Effects of vitamins (nicotinic acid, vitamin B 1 and biotin) on phototrophic hydrogen production by Rhodobacter sphaeroides ZX-5

The effects of vitamins (nicotinic acid, vitamin B 1 and biotin) on the growth and hydrogen production of Rhodobacter sphaeroides ZX-5 were investigated by batch culture in this study. The results showed that nicotinic acid, as a precursor of NAD +/NADH, plays a crucial role in effectively enhancing the phototrophic hydrogen synthesis during photo-fermentation process. Lack of nicotinic acid in hydrogen production medium resulted in the failure of photo-hydrogen production. In addition, though vitamin B 1 and biotin do not have direct impact on photo-hydrogen production, they are still essential and must exist in either growth medium or hydrogen production medium. Without either of them, photo-hydrogen production decreased seriously, regardless of the existence of nicotinic acid.

Enhanced biohydrogen generation from organic wastewater containing NH 4 + by phototrophic bacteria Rhodobacter sphaeroides AR-3

NH4+ is typically an inhibitor to hydrogen production from organic wastewater by photo-bacteria. In this experiment, biohydrogen generation with wild-type anoxygenic phototrophic bacterium Rhodobacter sphaeroideswas found to be sensitive to NH4+ due to the significant inhibition of NH4+ to its nitrogenase. In order to avoid the inhibition of NH4+ to biohydrogen generation by R. sphaeroides, a glutamine auxotrophic mutant R. sphaeroides AR-3 was obtained by mutagenizing with ethyl methane sulfonate. The AR-3 mutant could generate biohydrogen efficiently in the hydrogen production medium with a higher NH4+ concentration, because the inhibition of NH4+ to nitrogenase of AR-3 was released. Under suitable conditions, AR-3 effectively produced biohydrogen from tofu wastewater, which normally contains 50–60 mg/L NH4+, with an average generation rate of 14.2 mL/L·h. This generation rate was increased by more than 100% compared with that from wild-type R. sphaeroides.