木糖发酵产2,3-丁二醇菌株的筛选鉴定及其发酵条件优化

Screening and identification of 2,3-butanediol-producing strains by xylose fermentation and optimization of fermentation conditions

该研究以木糖为唯一碳源,通过富集培养、初筛和复筛、纯化,从蜗牛样品中筛选产2,3-丁二醇菌株,通过形态学观察和分子生物学技术对其进行鉴定。采用气相色谱(GC)法、气相色谱-质谱联用(GC-MS)法分析筛选菌株利用木糖发酵产物成分,利用木糖、葡萄糖与木糖混合糖发酵筛选高产2,3-丁二醇菌株,并对其发酵条件进行优化。结果表明,筛选出5株能利用木糖产2,3-丁二醇菌株(编号为SN1~SN5),经鉴定这5株菌均为变栖克雷伯菌属(Klebsiella variicola)。GC和GC-MS分析结果显示,2,3-丁二醇为筛选菌株利用木糖发酵的主要产物,其中菌株SN5发酵产2,3-丁二醇能力最强,在有氧条件下,2,3-丁二醇产量为(14.26±0.18)g/L。在葡萄糖与木糖2∶1的混合糖发酵条件下,发酵48 h产2,3-丁二醇(21.83±0.66)g/L。菌株SN5最佳发酵条件为蛋白胨添加量为5 g/L,发酵温度37℃,发酵时间48 h,初始pH值为6.0,初始木糖含量为80 g/L。在此优化条件下,2,3-丁二醇产量为(26.58±0.26)g/L,较优化前提高了89%,其转化率可达(0.53±0.01)g/g。

In this study,using xylose as the only carbon source,the 2,3-butanediol-producing strains were screened from snail samples through enrichment culture,primary screening and re-screening,purification,and the strains were identified by morphological observation and molecular biology techniques.The composition of xylose fermentation products of screened strains were analyzed by gas chromatography(GC)and gas chromatography-mass spectrometry(GC-MS).The strains with high yield of 2,3-butanediol were screened by xylose,glucose and xylose mixed sugar fermentation,and the fermentation conditions were optimized.The results showed that five strains(numbered as SN1-SN5)were selected to produce 2,3-butanediol from xylose,and all of them were identified as Klebsiella variicola.The results of GC and GC-MS analysis showed that 2,3-butanediol was the main product of xylose fermentation of the screened strains,and SN5 had the strongest fermentation ability to produce 2,3-butanediol,and the yield of 2,3-butanediol was(14.26±0.18)g/L under aerobic conditions.2,3-butanediol(21.83±0.66)g/L was produced in the fermentation condition of mixed sugar of glucose and xylose 2∶1 for 48 h.The optimal fermentation conditions of strain SN5 were peptone addition 5 g/L,fermentation temperature 37℃,time 48 h,initial pH 6.0 and initial xylose contents 80 g/L.Under the optimized conditions,the 2,3-butanediol yield was(26.58±0.26)g/L,which was 89%higher than that before optimization,and the conversion rate reached(0.53±0.01)g/g.