Isolation, identification and growth conditions of photosynthetic bacteria found in seafood processing wastewater.

Four photosynthetic bacteria, isolated from 14 samples taken from seafood processing plants, were identified as species of Rhodocyclus gelatinosus, belonging to the purple, non-sulphur bacteria of the family Rhodospirillaceae. Cultivation in synthetic medium under four different conditions indicated that all four strains gave maximum carotenoid and bacteriochlorophyll synthesis under anaerobic conditions in the light, with values of 11 to 12.6 and 102 to 108 mg/g dry cell wt, respectively. These values are 87% higher than the pigment content obtained from aerobic cultivation, although the cell biomass of all strains (1.7 to 2.3 g/l) was 22 to 38% higher under aerobic conditions. Protein content was always between 32 and 43%. The specific growth rates of all isolates in aerobic cultivation (0.04 to 0.06 h(-1)) were twice those in anaerobic conditions in the light. No growth occurred in anaerobic conditions in the dark.

Optimization for growth of Rhodocyclus gelatinosus in seafood processing effluents.

Tuna condensate was a better substrate than shrimp-blanching water or effluent from a frozen-seafood plant for growing Rhodocyclus gelatinosus under anaerobic conditions in the light. One strain out of four examined, R7, gave the highest biomass (4.0 g/l), cell yield (0.32 g cell/g COD), and COD removal (78%) in 1:10 (v/v) diluted tuna condensate. Shrimp-blanching water added to the tuna condensate further increased growth rate, biomass and COD removal. Optimal growth was at pH 7.0 and 3000 Lux light intensity. Acetate, pyruvate, glucose, glutamate, propionate or malate added to the tuna condensate did not increase cell yield, carotenoid or bacteriochlorophyll content or biomass protein. A maximum cell mass of 5.6 g/l (containing 50% protein) and 86% COD removal were obtained after 5 days' incubation under optimal conditions.