[Physiological characteristics of a low-pH tolerant strain Torulopsis glabrata RT-6]

With the aim of elucidating the physiological characteristics of a low-pH tolerant strain Torulopsis glabrata RT-6.

The intracellular pH, ATP level, the membrane bound H(+)-ATPase activity, the membrane fatty acid composition and the intracellular polyphosphate content of the parent strain CCTCC M202019 and the mutant strain RT-6 were determined and compared under different pH conditions.

Compared to that of the parent strain, the cell growth and pyruvate concentration of the mutant strain RT-6 were increased by 60.6% and 85.4% (56 h), respectively. Similarly, the strain RT-6 had higher intracellular pH compared to the control strain at external pH5.0, 4.5, and 4.0. The ATP content, the membrane bound H(+)-ATPase activity and the intracellular polyphosphate content of the mutant strain RT-6 were increased by 11.7%, 13.6%, and 3.5% at external pH 5.5, while at external pH 4.0, increased by 61%, 38.6%, and 30.8%, respectively. Furthermore, the mutant strain RT-6 exhibited higher content of the unsaturated fatty acids and higher membrane fluidity.

Discharging more intracellular H+ and inhibiting the intracellular H+ production contributed to the strain RT-6's higher intracellular pH, and therefore the acid tolerance.