Degradation of Tannins and Phytic Acid in Double-Low Rapeseed Meal by Aspergillus niger in Solid Fermentation and Optimization of Fermenting Condition

Three strains of Aspergillus niger(A.niger)(M-1,M-6 and 3.316) were used in solid fermentation of double-low rapeseed meal to study the degradation of tannins and phytic acid.Further investigation included the optimization of the fermentation.The results showed that all three strains significantly reduced the content of tannins and phytic acid(P0.05).The highest degradation was occurred in A.niger M-6 fermentation for 1d(P0.05).Different levels of moisture,temperature,pH and different nutrients(glucose,urea and mixture of minerals) were studied to optimize the fermenting performance of A.niger M-6 in solid fermentation.The highest degradation of tannins and phytic acid in double-low rapeseed meal was fermented 1d by A.niger M-6 at 25 ℃,pH 6,moisture 200% and addition with urea,glucose and minerals mixture,the content of tannins and phytic acid reduced from 1.32% to 0.28% and 2.81% to 0.63%,respectively.Besides,A.niger M-6 could increase the content of crude protein from 37.16% to 43.48% and in vitro the digestibility of crude protein from 75.32% to 79.15% in the optimal fermentation.This study may provide some basic data for the effective replacement of fish meal with double-low rapeseed meal.