西藏来源的植物内生酵母Wickerhamomyces rabaulensis生产γ-氨基丁酸

Production of γ-aminobutyric acid by the endophytic yeast Wickerhamomyces rabaulensis isolated from Tibetan plant

摘要:

【目的】对西藏地区分离的一株植物内生维克汉姆酵母Wickerhamomyces rabaulensis JT229生产γ-氨基丁酸(γ-aminobutyric acid，GABA)的条件进行研究，并考察胁迫处理对生产的影响。【方法】利用26S rDNA序列进行菌株鉴定，考察葡萄糖和木糖对W. rabaulensis JT229生产GABA的影响，并利用添加乙酸、乙醇和高温等胁迫条件提升其发酵生产GABA的能力。【结果】W. rabaulensis JT229可以利用葡萄糖和木糖生产GABA，并且在适当的高温、乙酸和乙醇的胁迫诱导下胞外GABA浓度明显提升，产量分别为80.07、67.02、104.15 mg/L，分别是对照条件下的2.15、1.85和2.87倍，且胞内也检测到存在一定浓度的GABA。在添加5 g/L乙酸和37 °C高温胁迫的条件下，胞内ROS水平和细胞膜透性均有明显提高；添加3 g/L乙酸的条件与对照组相比，胞内ROS水平有所下降，但是细胞膜透性有明显提升；在37 °C的胁迫条件下胞内GABA含量明显下降。胞外的GABA产量提升推测是由于胁迫导致胞内GABA外排增多导致的。【结论】本研究首次在国内外分离鉴定了内生酵母W. rabaulensis，并发现菌株W. rabaulensis JT229具有生产GABA的潜力，此外，利用胁迫处理促进了该菌株的GABA胞外生产，为进一步开发利用酵母资源生产GABA及富含GABA的产品提供了基础。

Abstract:

[Objective] To promote the production of γ-aminobutyric acid (GABA) by an endophytic yeast Wickerhamomyces rabaulensis JT229 isolated from plants in Tibet. [Methods] The D1/D2 region sequence of 26S rRNA gene was used for strain identification. Glucose and xylose were tested for GABA production. In addition, stress treatments, including high temperature and high concentration of ethanol and acetic acid, were investigated to increase the extracellular production of GABA by the strain. [Results] Wickerhamomyces sp. JT229 was identified as Wickerhamomyces rabaulensis, which produced GABA using glucose and xylose, and the GABA production was enhanced under the moderate stress of high temperature, acetic acid and ethanol. The extracellular production of GABA was 80.07, 67.02 and 104.15 mg/L under the above stress conditions, which were 2.15, 1.85 and 2.87 times those of the control conditions, respectively, and the intracellular accumulation of GABA was also detected. Under the conditions of 5 g/L acetic acid and 37 °C, the intracellular ROS level and cell membrane permeability increased more markedly than those under the control conditions. Compared with the control group, 3 g/L acetic acid lowered the intracellular ROS level while enhanced the cell membrane permeability. Under 37 °C, the content of intracellular GABA dropped. Therefore, we inferred that the increased extracellular production of GABA was resulted from its increased intracellular secretion. [Conclusion] This is the first time that endophytic W. rabaulensis was identified. We revealed that W. rabaulensis strain JT229 isolated from Tibet had the potential to produce GABA, and also demonstrated the enhanced production of GABA under stress treatments. The results facilitated further development and utilization of yeast strains for production of GABA and GABA-containing products.