Biochemical composition of new yeasts and bacteria evaluated as food for bivalve aquaculture

The biochemical compositions of seven strains of marine bacteria and six strains of yeast-all isolated from an Australian waterway-were compared with two well-studied yeast strains, Candida utilis and Saccharomyces cerevisiae, to assess their nutritional quality for bivalve aquaculture, Protein was a major constituent of both yeast and bacteria (25-49% dry weight), with lipid a minor component (2.5-9.0%), Carbohydrate in yeast was 21-39% of dry weight, bacteria had 2.5-11%. Ash ranged from 4.7 to 14% dry weight in 11 of the yeast and bacteria strains; the remaining species, all bacteria, had high levels (29-40%). Nucleic acid ranged from 3.3 to 8.4% dry weight in the yeast and bacteria. The amino acid compositions were similar in the strains, and closely matched those of Saccostrea commercialis larvae and spat indicating a high protein quality, Glucose was a major sugar in the polysaccharide of both yeast and bacteria (12-73% of total sugars); mannose was in high concentrations in the yeast (24-65%), Both polyunsaturated fatty acids (PUFAs) 20:5n-3 and 22:6n-3 were absent in all strains, and thus if the strains are to be used in bivalve aquaculture, they would need to be supplemented with live algae rich in these PUFAs. High levels of good quality protein, however, indicate their potential to provide important nutrients in a mixed diet.