Recent studies on production of biofuel and biopolyesters with anoxygenic phototrophic bacteria

Recent studies on the production of molecular hydrogen and biopolyesters by anoxygenic phototrophic bacteria are described in this paper. A halotolera nt strain of Rhodobium marinum, an indigenous strain of Rhodopseudomonas pa lustris, and a mutant of the wild strain Rhodobacter capsulatus lacking hyd rogenase activity, were investigated for hydrogen production. The penetrati on of light into a photobioreactor and the effect of light/dark cycles on h ydrogen production were analyzed using Rba. sphaeroides. A combined system with hydrogen production by phototrophic bacteria and a fuel cell has been investigated for light energy conversion to electricity. The photobiologica l hydrogen production using the combination of a marine green alga Chlamydo monas sp. and a marine phototrophic bacterium Rhodovulum sulfidophilum, and spiral tubular and double-phase photobioreactors were investigated. As for the biopolyesters, a marine phototrophic bacterium, Rhodopseudomonas sp., was reported to accumulate poly-3-hydroxybutyrate (PHB) under microaerobic and photoheterotrophic conditions. The feasibility of a photoproduction pro cess for both H-2 and the PHB-containing biomass of Rp. palustris have been tested using a tubular system with limiting amounts of fixed nitrogen. A m ethod of producing polyhydroxyalkanoate from enzymatically treated crude sa go starch was studied using Rba. sphaeroides. Induction of phototrophic bac terial growth from anaerobic granules under light conditions (100 muE m(-2) s(-1)) and the performance of a lighted upflow anaerobic sludge blanket (L UASB) reactor for PHB production and wastewater treatment were investigated . The average PHB production rate of the biomass in the effluent from the L UASB reactor was 6.6-14.0 mg l(-1)-reactor d(-1) using acetate-based media and the average PHB content based on the dry bacterial biomass was 15.1-25. 3%. The PHB concentration increased by a secondary incubation of the efflue nt from the LUASB reactor with sodium acetate under anaerobic light conditi ons. The UASB granules can decompose a variety of organic substances; there fore, the LUASB method appears to be appropriate for wastewater treatment a nd the production of phototrophic bacteria and PHB from various wastewaters .