Effect of solid state fermentation on nutrient composition of selected feed ingredients

Abstract

Solid-state cultivation of the fungus Aspergillus niger and the bacterium Bacillus coagulans was carried out to enrich the nutritional value of plant ingredients like soybean meal, mixed ingredients and wheat bran to use as aquafeed ingredients. Fermentation of soybean meal (FSBM) using B. coagulans for 48 h resulted in significant (p<0.05) increase in the crude protein content (@ 3 to 7%) with concurrent decrease in nitrogen free extract (NFE) (11 to 16 %). Among the essential amino acids, valine (7%), isoleucine (2%), leucine (2%), lysine (93%) and tryptophan (42%) showed substantial increases in FSBM after 48 h. Solid state fermentation (SSF) of ingredient mix using A. niger NCIM 616 resulted in initial reduction of crude protein content during the first 48 h followed by significant (p<0.05) increase of 4 to 14% during the course of fermentation. The crude fat content showed a 35% increase in 96 h. Nitrogen free extract though increased marginally (4%) at 48 h showed significant reduction (17%) at 96 h. A marginal increase in arginine, valine and methionine levels were also observed in the fermented ingredient mix (FIM). Solid state fermentation of wheat bran using A. niger S14 (a mangrove isolate) had resulted in substantial increase in crude protein level (57 to 66%) as compared to that of raw wheat bran. The carbohydrate content in wheat bran showed substantial reduction (75 to 39%) during the course of fermentation. Essential amino acids like, histidine, threonine, valine, isoleucine and lysine showed increase during SSF. The results of the present study show that B. coagulans and the selected strains of A. niger can be used for nutritional enrichment of plant ingredients for further use in aquafeed formulations.