等离子体诱变凝结芽孢杆菌提高木糖利用能力高产L-乳酸

为进一步提高凝结芽孢杆菌发酵木糖生产L-乳酸的产量和转化率，以实验室保存的一株能利用木糖产L-乳酸的野生型凝结芽孢杆菌菌株NL01为出发菌株，通过等离子体诱变育种技术和平板菌落初筛、摇瓶复筛，最终得到一株木糖耐受力强、L-乳酸产量高、遗传特性稳定的正向突变菌株NL-CC-17。该突变菌株是目前已报道的木糖耐受力最高的菌株。当以100 g/L的木糖为底物，50 ℃发酵72 h后，L-乳酸产量达到82.30 g/L，糖酸转化率为92.37%，L-乳酸产量较出发菌株提高21.51%，糖酸转化率提高了16.00%。通过初步优化发酵条件，确定该菌株最佳发酵温度为50 ℃，实验范围内最佳发酵pH值为5.5。

Improved Xylose Utilization of Bacillus coagulans by Atmospheric and Room Temperature Plasma Mutation for Production of Lactic Acid

To further enhance the production and yield of converting xylose to L-lactic acid, an atmospheric- and room
temperature-plasma (ARTP) mutation system was employed to induce the mutation of Bacillus coagulans NL01, a wild-type
strain for production of L-lactic acid from xylose. A positive mutant, named as NL-CC-17, was obtained through enrichment and
screening. Compared with that of previously reported strains, NL-CC-17 had an improved tolerance to xylose. This strain was
capable of converting 100 g/L xylose into 82.30 g/L L-lactic acid after being cultured at 50 ℃ for 72 h with a yield of 92.37%. The
concentration of L-lactic acid was increased by 21.51% and the yield by 16.00%. After preliminary optimization of fermentation
conditions, the optimal fermentation temperature was determined as 50 ℃ and the optimal pH as 5.5.