Bio-processing of Linseed Oil-Cake through Solid State Fermentation by Non-Starch Polysaccharide Degrading Fish Gut Bacteria

Abstract

Cellulose and hemicellulose (xylan) are the most common Non-Starch Polysaccharides (NSPs) present in plant ingredients that exhibit anti-nutritional effect. Degradation of cellulose and xylan has been investigated under solidstate fermentation (SSF) using oil-cakes, viz., groundnut oil-cake (GOC), mustard oil-cake (MOC), sunflower oilcake (SOC), sesame oil-cake (SeOC) and linseed oil-cake (LOC) as substrates. Finally LOC was considered in the present study as it contained maximum amount of cellulose (17.51 ± 0.87 g 100 g-1) and xylan (13.02 ± 0.66 g 100 g-1). Bio-processing of LOC was carried out through SSF in two different combinations utilizing efficient cellulaseand xylanase-producing strains, Bacillus pumilus KF640221 (Set-I) and Bacillus tequilensis KF640219 (Set-II), isolated previously from the proximal intestines of rohu, Labeo rohita and silver carp, Hypophthalmichthys molitrix, respectively. Analysis of the fermentation sets revealed that B. pumilus KF640221 in Set-I was most effective in reducing the cellulose and xylan contents of LOC. Besides, SSF under optimized conditions caused considerable increase in crude protein, crude lipid, total free amino acids and total free fatty acids along with reduction in the contents of other anti-nutritional factors, e.g., crude fiber, tannins, phytic acid and trypsin inhibitor. High performance liquid chromatography (HPLC) analysis of raw and fermented LOC of Set-I indicated that concentrations of methionine, histidine, tryptophan, phenylalanine, threonine were increased considerably. Further research is inevitable to explore the possibilities for utilization of SSF-processed LOC to set up a strategy for sustainable utilization of low cost oil-cakes as animal feed ingredients.