Isolation and growth of the phototrophic bacterium Rhodopseudomonas palustris strain B1 in sago-starch-processing wastewater

An indigenous strain of the purple non-sulphur phototrophic bacterium, Rhodopseudomonas palustris strain B1, was selected for the utilization and treatment of wastewater from a sago-starch-processing decanter. Growth of Strain B1 under anaerobic±light conditions in the carbohydrate-rich ef ̄uent was optimized by using 50% (v/v) ef ̄uent diluted in a basal minimal mineral medium with the addition to 0.1% (w/v) yeast extract. The optimum level of nitrogen source supplement, ammonium sulphate, was 1.0 g/l. Highest cell mass concentration was achieved by using tungsten lamps as the light source with a light intensity of 4 klux. Under these optimal conditions, a maximum biomass of about 2.5 g dry cell/l with a pigment content of about 1.1 mg carotenoid/g dry weight cell was achieved after 96 h of anaerobic cultivation. There was a 77% reduction in the chemical oxygen demand (COD) of the ef ̄uent. A cell yield of about 0.59 g dry weight cell/g COD was obtained.