Microbially Bioprocessed Soybean Protein and its Effect on Growth Performance and Immune Response of Yellow Perch Perca flavescens

We evaluated growth and immunological performance of Yellow Perch after a 60-day feeding trial using primary dietary protein sources of either fish meal (FM), solvent extracted white flake (WF), defatted soybean meal (SBM), solid-state bioprocessed white flake (SWF), solid-state bioprocessed soybean meal (SSBM), liquid-state bioprocessed white flake (LWF), or liquid-state bioprocessed soybean meal (LSBM). The conversion process used Aureobasidium pullulans to metabolize carbohydrates and anti-nutritional factors in soybeans into single cell protein. On a dry basis, protein levels increased from an average of 53.3% in base feedstocks to 58.2% in solid-state products, and 61.1% for liquid-state products. Trypsin inhibitor activity decreased from 4,428 TIU/g (db) in base feedstocks to 3,458 TIU/g in solid-state and 1,359 TIU/g for liquid-state. Fish fed both LSBM (90.80±8.40%) and LWF (80.78±8.41%) displayed greater relative growth than FM (71.88±9.18%), although not significantly different (P>0.05). Solid-state bioprocessing significantly improved relative growth over the un-converted feedstocks, but was significantly lower than liquid-state or FM. Processing had a significant effect on performance, while feedstock provided an insignificant effect. No significant differences were found in the spleen somatic index, visceral fat index, and the fillet yield. Fish fed LSBM produced the highest fillet yield (40.69±0.62%). Hepatosomatic Index was found to be significantly higher in FM than in SBM and WF (P<0.001). Macrophage respiratory burst activity was found to be greatest in the FM, SWF, and WF treatments, while LWF was significantly less than FM (P=0.001).