Single cell protein such as bacteria l meal are rich in protein sources (>50%) with high levels of nucleotides and are very palatable and devoid of anti-nutritional factors. S ingle cell meal (SCM) (Methylorubrum sp -strain KB203, JUVTM, KnipBio, Lowell, MA) are grown by aerobic fermentation at 30° C and dried to make a feed ingredient . Eight iso-nitrogenous (48 % crude protein) and isolipidic (13%) experimental diets were formulated and prepared to replace menhaden fish meal protein ( MFP, 59.5% crude protein) by SCM (50.4% crude protein) for juvenile black sea bass, Centropristis striata. Test diets were prepared replacing 0, 7.4, 14.8, 29.6, 44.4, 59.2, 74.0, and 8 8.8% of MFP by supplementing SCM at 0 , 2.5, 5, 10, 15, 20, 25 and 30% in the diets. A control diet (0% replacement) was formulated with high fish meal (30 %) and other practical protein sources, including solvent extracted soybean meal, and poultry by product meal. All other nutrients in the diets were added according to recent information on nutrient requirements for black sea bass. Twenty fish were stocked in each of twenty-four 75-L tanks in a controlled-environment laboratory of a recirculating aquaculture system and each test diet was fed to triplicate groups of fish (mean weight = 2.68 ± 0. 14 g) for 56 days. Fish were fed twice per day (09:00 and 16:00 h) to apparent satiation. The water salinity was 34 mg/L and temperature ranges 22 -24 ° C and all other water quality parameters were maintained optimal during the feeding trial.
Growth performance, including weight gain, specific growth rate and feed utilization were evaluated. The percent body weight gain among the fish fed the test diets were not significantly different (P<0.05) although the group fed 15% SCM showed the highest mean value (Figure 1). Survival was higher than 90% among treatments with no significant differences. The proximate composition, amino acid and fatty acid analysis of diets and fish tissues were analyzed.
Results to date suggest that black sea bass juveniles are able to utilize high levels of single cell protein replacing fishmeal without affecting fish growth. The body composition data will be compared with the growth data, and an optimal SCM supplementation level in the diet of juvenile black sea bass will be recommended.