| Abstract:This study adopted Bacillus subtilis and Aspergillus oryzae to ferment corn meals in solid state conditions to optimized fermentation conditions, and then to evaluate the effect of solid state fermentation on the nutritional ingredient, saccharide, the composition and relative molecular mass of corn starch and the amount of metabolites by microorganism. To accumulating reference for improving the quality of energy feed according to the fermentation technique.This experiment adopted 4×3 (4 factors and 3 levels) factorial orthogonal design to optimize fermentation conditions, which included culture time, inoculation volume, water content and the addition amount of ammonium sulfate. The level of soluble sugar in fermentation products was an indicator for selecting optimum fermentation conditions. The results showed that:The optimum fermentation conditions of B. subtilis was that corn meals contained 50% moisture, added 1.5% ammonium sulfate, inoculated 15% spore suspension, and fermented 72 h. Under these conditions, the content of soluble sugar increased from 11.83% to 32.19% in fermentation products. The optimum fermentation conditions of A. oryzae was that corn meals contained 60% moisture, added 2% ammonium sulfate, inoculated 15% spore suspension, and fermented 48 h. The content of soluble sugars increased 134.23% in fermentation substrate. Corn meals fermented with B. subtilis was better than A. oryzae, because it had a higher soluble sugar content than A. oryzae.Experiment 2 Effect of Bacillus subtilis and Aspergillus oryzae fermentation on nutritional quality of corn mealsCorn meal was respectively fermented by B. subtilis and A. oryzae in the optimum fermentation conditions to study the variation of nutrients before and after fermentation, and further to investigate the fermentation effect of corn meal respectively fermented by B. subtilis and A. oryzae. To compare the different fermentation effects on each microorganism fermented corn meals. The results showed that:(1) The quantity of corn starch significantly decreased, which the main reduction was amylopectin, after fermentation. The quantity of corn starch reduced 44.48%(P<0.01), which the amount of amylopectin and amylose respectively deceased 57.35%(P<0.01) and 4.86%(P<0.05) after fermentation with B. subtilis. And the amount of amylopectin and amylose respectively deceased 43.57%(P<0.01) and 7.23%(P<0.05) after fermentation with A. oryzae.(2) The relative molecular mass of starch significantly decreased in fermentation substrate. The relative molecular mass of starch in B. subtilis and A. oryzae fermentation substrate were respectively 3.86×105 and 4.80×105, which respectively decreased 53.04% and 41.61% as compared with un-fermentation corn meals.(3) The amount of soluble sugar significantly increased in corn meals after fermentation. The soluble sugar content in B. subtilis and A. oryzae fermentation substrate respectively increased 120.20%(P<0.01) and 104.63%(P<0.01), which the level of reducing sugar respectively increased 321.72%(P<0.01) and 265.16%(P<0.01), the quantity of dextrin.respectively enhanced 76.31%(P<0.01) and 47.09%(P<0.01).(4) The acidity significantly increased, meanwhile pH significantly decreased in corn meals after fermentation. The acidity in B. subtilis and A. oryzae fermentation substrate respectively enhanced 2.09 mg/g (P<0.01) and 2.54 mg/g (P<0.01), but the pH value decreased 0.79 (P<0.01) and 1.21 (P<0.01).(5)The extract of corn meals which fermented by B. subtilis inhibited Escherichia coli and Staphylococcus aureus, and the growth inhibition on S. aureus was greater than on E. coli.(6) Different microbial fermentation of corn meal had a different effect on various nutrients. The amount of DM of B. subtilis fermentation substrate lost greater (P<0.01) than A. oryzae fermentation substrate, and the level of soluble sugar of B. subtilis fermentation substrate increased 14.49%(P<0.01) than A. oryzae fermentation substrate.These works indicate that fermentation with B. subtilis and A. oryzae mainly decrease the quantity of amylopectin, significantly degradate the relative molecular mass of starch, mean while product some metabolites in solid state conditions.
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