This study aimed to improve the nutritional value and utilization of soybean meal (SBM) used as feed ingredient for shrimp by an approach of solid‐state fermentation with Bacillus subtilis E20. The protein content and B. subtilis E20 proliferation significantly increased, as the initial moisture increased from 30% to 50% during fermentation. Compared with SBM, the protein content of FSBM increased by 19% after fermentation, accompanied by an increase of 18.75% in the total hydrolyzed amino acids. The free amino acid profile and content in FSBM also obviously increased by 374.9% compared with SBM. The FSBM is a good substitute for fish meal (FM) in a diet with 37% protein and 7% lipid content. The maximal replacement levels of FM in shrimp diet with SBM and FSBM were 37.42% and 61.67%, respectively, based on the feed efficiency estimated by a broken‐line analysis. The B. subtilis E20‐FSBM can be a potential protein source used as a replacement for FM in shrimp diet.

The potential of Bacillus subtilis E20-fermented soybean meal (FSBM) as a partial alternative component of fish meal (FM) in fed diets of orangespotted grouper (Epinephelus coioides) was evaluated in this study. An FM-based diet and seven diets containing 10%, 20% and 30% and 10%, 20%, 30% and 40% of FM replaced by soybean meal (SBM) and FSBM, respectively, were fed to grouper for 84 days to evaluate possible substitution levels of FM by tracking growth performance, digestive enzyme activity and morphological changes in the liver and distal intestine. No significant differences in survival and muscle composition of grouper were found between controls and treatments. Growth performance and feed efficiency of fish fed diets with FM replaced by FSBM up to 30% were not significantly different from controls, whereas significantly decreased growth performance and feed efficiency occurred with diets containing >20% of SBM. Based on the feed efficiency, the maximum substituted levels of FM by SBM and FSBM in grouper diets were 18.36% and 29.32%, respectively, based on broken-line analyses. Histopathological changes in the liver and distal intestine, and significantly lower activity levels of digestive enzymes, including pepsin in the stomach and trypsin, chymotrypsin, amylase and lipase in the distal intestine, were found in fish fed a diet containing 30% of FM replaced by SBM. However, these parameters were improved by the substitution of FSBM. It is therefore believed that FSBM has great potential to be used as a protein source in grouper diets in partial replacement of FM.

An experiment was conducted to evaluate the potential of a Bacillus subtilis E20-fermented mixture (FSFEM) containing soybean meal (SBM) and Eisenia fetida earthworm meal (EM) at a ratio of 4:1 to increase the methionine level in order to satisfy the methionine requirement of white shrimp, Penaeus vannamei in a diet with fish meal (FM) completely replaced by mixtures. B. subtilis E20 fermentation improved the mixture's palatability and utilization based on better growth performance in comparison to shrimp fed FSEM (contains fermented SBM and EM at a ratio of 4:1) diets. FSFEM is a good substitute for FM. Maximal replacement levels of FM with FSFEM were 80% in a shrimp diet with 37% of crude protein and 7% of crude lipid based on weight gain and 100% based on feeding efficiency. In addition, shrimp fed experimental diets had no significant differences in survival after being challenged by Vibrio alginolyticus. It is suggested that B. subtilis E20-FSFEM has the potential to replace FM in cultured shrimp diets.

Six fish meal basal diets supplied with 0 (control), 0.25, 0.5, 1, 2.5 and 5 g kg À1 of choline chloride, resulting in choline levels of 2.57, 2.67, 2.94, 3.84, 4.99 and 7.71 g kg À1 , respectively, were fed to giant grouper, Epinephelus lanceolatus, for 56 and 30 days to evaluate the growth and lipid metabolism, and stress tolerance respectively. In the first trial, fish fed different levels of cholinecontaining diets for 56 days had no significant difference in weight gain, survival and feeding efficiency. Fish fed increased levels of dietary choline, however, tended to have decreases in the hepatic somatic index; lipids, triglycerides, and cholesterol in liver; and triglycerides and cholesterol in serum. A decrease of lipid content in dorsal muscle was recorded in fish fed the diets containing choline >2.94 g kg À1 . Additionally, dietary choline improved the reactions of fish to ammonia stress, including survival and behavioural responses, in fish fed diets containing choline levels >2.94 g kg À1 . These findings indicate that choline plays important roles in lipid metabolism and stress tolerance in giant grouper.