S139: Oligosaccharides removal and nutritional enhancement of soybean meal via solid state fermentation using Aspergillus oryzae

Soybean meal (SBM) is used as the main protein source for monogastric animals. The anti-nutritional factors in SBM, like oligosaccharides, trypsin inhibitor and large protein size, limit its usage in feed industry. We used Aspergillus oryzae solid state fermentation to degrade these anti-nutritional factors and add value to SBM. Twenty grams of SBM with 50% moisture was inoculated with 1 ml Aspergillus oryzae (ATCC 12892) spore solution (2.28 * 10⁷ spore/ml) and fermented at 30 ^oC for up to 7 days. Aspergillus orzyae growth was monitored and SEM images showed that the fungus first spread among substrate and hyphae became stronger after fully spreading. After 36 hr inoculation, spores were generated for lack of nutrients. Oligosaccharides (raffinose and stachyose) were totally degraded from the original 9.48 mmol/100g and trypsin inhibitor decreased to non-detectable level from the original 10.735 TIU/mg after 36 hr fermentation. Protein content increased from 50.47% (w/w) to 58.93% (w/w) after 36 hr and to 63.09% (w/w) after 7d fermentation. Large protein molecules were degraded, which was demonstrated by the increased Trichloroacetic acid (TCA) protein content from 2.18% (w/w) to 51.1% (w/w) after 7d fermentation. Unsaturated fatty acid such as palmitoleic and linoleic content increased. Total amino acid, lysine, methionine and tyrosine content increased from 49.13%, 3.24%, 0.72%, 1.84% to 55.58%, 3.54%, 0.8% and 1.94%, respectively. Available lysine content increased from 3.06% to 3.25%. Aspergillus oryzae fermentation greatly enhanced the nutritional value of SBM. The low cost soy fermented product has wider potential usage in livestock field industry.