寄生曲霉CICC40365利用木糖产L-苹果酸的发酵条件优化

【目的】为提高L-苹果酸产量及木糖利用率,以寄生曲霉(Aspergillus parasiticus CICC40365)为菌种,木糖为碳源,对其发酵工艺及木糖代谢途径进行初步研究。【方法】采用单因素试验和响应曲面法(Box-Behnken设计)对培养基和发酵条件进行优化。【结果】获得最佳培养基配方为:木糖100.0 g/L、硫酸铵2.0 g/L、酵母浸粉3.0 g/L、硫酸镁0.20 g/L、硫酸锰0.15 g/L、硫酸亚铁0.08 g/L、碳酸钙80.00 g/L,L-苹果酸的产量为53.58 g/L,较优化前提高40.5%。发酵条件较好组合为:接种量为8%(体积比)、摇瓶装液量60 mL/250 mL、发酵温度32°C、摇床转速170 r/min、发酵周期8 d,L-苹果酸的产量为55.47 g/L。Mg2+、Mn2+对木糖代谢中相关酶的影响研究结果表明,木酮糖激酶在该菌株代谢木糖过程中起着重要作用。【结论】寄生曲霉CICC40365能够较好地利用木糖发酵产L-苹果酸,其产量及木糖的利用效率均得到提高。

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

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.