Optimization of fermentation process for L-malic acid with xylose by Aspergillus parasiticus CICC40365

Abstract:

[Objective] To increase the yield of L-malic acid and the utilization rate of xylose, the Aspergillus parasiticus CICC40365 was used as the strain to produce L-malic acid with xylose, and the fermentation technology in shake flask was investigated in the work. [Methods] The medium components and fermentation conditions were optimized through single factor experiments and response surface methodology. [Results] The optimal medium components were as follows: the xylose, (NH4)2SO4, yeast extract powder, MgSO4, MnSO4·H2O, FeSO4·7H2O and CaCO3 were 100.0, 2.0, 3.0, 0.20, 0.15, 0.08 and 80.00 g/L, respectively. The yield of malic acid from the optimal condition was 53.58 g/L and it was 40.5% higher than that of original condition. The reasonable fermentation conditions were inoculum ratio 8% (V/V), the liquid volume in the shake flask 60 mL/250 mL, fermentation temperature 32 °C, rotation speed 170 r/min, leading to the 55.47 g/L yield of L-malic acid. Meanwhile, the effect of Mg2+, Mn2+ on the relative enzymes in the xylose metabolism indicated that the xylulokinase played an important role in the process of xylose metabolism. [Conclusion] The xylose can be better utilized to produce L-malic acid through fermentation with Aspergillus parasiticus CICC40365, and the yield of L-malic acid and utilization rate of xylose were improved effectively through this experiment.

Key words:Aspergillus parasiticus, Xylose, L-malic acid, Response surface methodology, Xylulokinase