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

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.