Limiting factor of nitrogenase system mediating hydrogen production of Rhodobacter sphaeroides S

Cheese whey to biohydrogen and useful organic acids: A non-pathogenic microbial treatment by L. acidophilus

The burgeoning organic waste and continuously increasing energy demands have resulted in significant environmental pollution concerns. To address this issue, the potential of different bacteria to produce biogas/biohydrogen from organic waste can be utilized as a source of renewable energy, however these pathogenic bacteria are not safe to use without strict contact isolation. In this study the role of safe food grade lactic acid bacteria (Lactobacillus spp.) was investigated for production of biogas from cheese waste with starting hexose concentration 32 g/L. The bacterium Lactobacillus acidophilus was identified as one of the major biogas producers at optimum pH of 6.5. Further the optimum inoculum conditions were found to be 12.5% at inoculum age of 18 h. During the investigation the maximum biogas production was observed to be 1665 mL after 72 hours of incubation at pH 6.5. The biogas production was accompanied with production of other valuable metabolites in the form of organic acids including pyruvate, propionate, acetate, lactate, formate and butyrate. Thus this research is paving way for nonpathogenic production of biohydrogen from food waste.

Progress toward a biomimetic leaf: 4,000 h of hydrogen production by coating-stabilized nongrowing photosynthetic Rhodopseudomonas palustris

Intact cells are the most stable form of nature's photosynthetic machinery. Coating-immobilized microbes have the potential to revolutionize the design of photoabsorbers for conversion of sunlight into fuels. Multi-layer adhesive polymer coatings could spatially combine photoreactive bacteria and algae (complementary biological irradiance spectra) creating high surface area, thin, flexible structures optimized for light trapping, and production of hydrogen (H(2)) from water, lignin, pollutants, or waste organics. We report a model coating system which produced 2.08 +/- 0.01 mmol H(2) m(-2) h(-1) for 4,000 h with nongrowing Rhodopseudomonas palustris, a purple nonsulfur photosynthetic bacterium. This adhesive, flexible, nanoporous Rps. palustris latex coating produced 8.24 +/- 0.03 mol H(2) m(-2) in an argon atmosphere when supplied with acetate and light. A simple low-pressure hydrogen production and trapping system was tested using a 100 cm(2) coating. Rps. palustris CGA009 was combined in a bilayer coating with a carotenoid-less mutant of Rps. palustris (CrtI(-)) deficient in peripheral light harvesting (LH2) function. Cryogenic field emission gun scanning electron microscopy (cryo-FEG-SEM) and high-pressure freezing were used to visualize the microstructure of hydrated coatings. A light interaction and reactivity model was evaluated to predict optimal coating thickness for light absorption using the Kubelka-Munk theory (KMT) of reflectance and absorptance. A two-flux model predicted light saturation thickness with good agreement to observed H(2) evolution rate. A combined materials and modeling approach could be used for guiding cellular engineering of light trapping and reactivity to enhance overall photosynthetic efficiency per meter square of sunlight incident on photocatalysts.