Hydrogen Production from the Photosynthetic Bacterium, Rhodopseudomonas Sphaeroides

摘要

The photosynthetic bacterium, Rhodopseudomonas sphaeroides can produce H sub 2 gas under certain conditions when supplied with an appropriate reduced carbon source. It was determined that the enzyme nitrogenase is responsible for this activity. It was observed that maximum rates of H sub 2 biosynthesis were achieved when the organism was grown anaerobically in the light in a medium containing minimal amounts of reduced nitrogen. An atmosphere low in N sub 2 also increased H sub 2 yields. The organism can utilize lactate, malate, fructose or sucrose to produce H sub 2 . Glucose and gluconate are not normally so utilized. The energy charge, as described by Atkinson, was about 0.5 regardless as to whether the organism was producing H sub 2 . Total nicotinamide adenine dinucleotide levels were three-times that of nicotinamide adenine dinucleotide phosphate. The steady-state ratios of reduced to oxidized forms of both of these compounds was about 0.2. Ammonium ion completely inhibited H sub 2 production at 1 mM. O sub 2 inhibited H sub 2 production completely and irreversibly in vivo when present above 8% in the atmosphere. N sub 2 did not completely suppress H sub 2 production at any level. Carbon monoxide at 10% in the atmosphere did not affect metabolism or inhibit H sub 2 production. Monofluoroacetate inhibited H sub 2 production from 10 to 70% depending on the strain and the carbon compound used for substrate. For cells grown on malate, fructose, or glucose, storage material formed was almost entirely polyglucose. During H sub 2 production, amino acids were not produced, even when an amino group donor such as glutamate was present. Metabolic pathways in glucose utilization were strain dependent. CO sub 2 fixation in cultures producing H sub 2 photoheterotrophically is minimal and occurs primarily via phosphoenolpyruvate carboxylase. (ERA citation 06:028352)