Potential Use of the Phototrophic Bacterium, Rhodopseudomonas palustris, as an Aquaculture Feed

An indigenous strain of the phototrophic bacterium, Rhodopseudomonas palustris, was mass cultured in sago wastewater under anaerobic-light conditions. The bacterial cell mass was analyzed for nutritional value and tested for toxicity and acceptability as an aquaculture feed. Proximate analysis indicates a macrocomposition of 40% crude protein, 0.64% crude lipid and 2.09% crude fibre. The essential amino acids (EAA) of the bacteria biomass comprise 53% of its true protein content, and all EAA present were found to be within the dietary requirements of penaeid shrimps at the 35-55% dietary protein level. Ex­perimental feeding trials carried out on brine shrimp (Artemia) larvae showed that the bacteria, whether given as a sole diet or as a feed supplement, supported larval survival (42-53%) and growth (78-88%) with no significant differences. Larval survival of brine shrimps fed on bacteria or bacteria-supplemented diets (42-53% survival) were also compa­rable to those fed on a bacteria-free mixed diet of commercial prawn feed and the blue­green algae Spirulina (60%). However, after 7 days of rearing, brine shrimps fed the lat­ter mixed diet were significantly larger (121% increase in mean body length ) than those fed the bacteria or bacteria-supplemented diets (78-88%).