LAUSR

Due to the high price of animal feed additive, a number of studies have been carried out to find an alternative diet with comparable nutritional profile and cost competitiveness. The photosynthetic bacterium Rhodopseudomonas faecalis PA2 was recently proposed as a new carotenoid producer with relatively high biomass production but the mass production using a cheap substrate remains unclear. In this study, Rps. faecalis PA2 was cultivated in domestic wastewater. The optimum light intensity and agitation speed were 4000 lux and 150 rpm, respectively. Batch cultivation in a photo-bioreactor showed that specific growth rate was 1.61/day with the maximum biomass production of 33.9 g/L. Carotenoid yield, carotenoid production rate and carotenoid productivity were found to be 7.2 mg/g, 74.3 and 40.9 mg/L day, respectively. The nutritional profile of the freeze-dried biomass contained 64.8% protein and 10.6% lipid. The contents of essential amino acids accounted for approximately 72.6% of the whole protein content which is comparable with dietary amino acids required for penaeid shrimp. The amounts of unsaturated fatty acids were higher than saturated fatty acids consisting of polyunsaturated fatty acid including omega-3 (alpha-linolenic acid [18, n − 3]) and omega-6 fatty acids. Cultivation of this bacterium in domestic wastewater is considered a promising technology for microbial feed additive production with price competitiveness. Moreover, biochemical composition of Rps. faecalis grown in domestic wastewater is first reported in this study.