Rhodopseudomonas palustris TN1 was isolated from Songkhla Lake, Thailand. It phototrophically generates H-2 from the predominant volatile fatty acids (VFAs) produced from microbial dark-fermentations of palm oil milling effluent; yields from 20 mM butyrate, acetate and propionate were 4.7, 2.5, and 1.7 mol H-2 mol VFA(-1) with light efficiencies of 1.8, 1, and 0.2%, respectively. Optimum conditions were pH 7 and 3000 lux, although production was reduced by only 33% at 1000 lux. CO2 evolution never exceeded 9 mmol mol VFA(-1).