Effect of Sodium Chloride and Cadmium on the Growth, Oxidative Stress and Antioxidant Enzyme Activities of Zygosaccharomyces rouxii

Zygosaccharomyces rouxii is a salt-tolerant yeast species capable of removing cadmium(Cd) pollutant from aqueous solution. Presently, the physiological characteristics of Z. rouxii under the stress of sodium chloride(NaCl) and Cd are poorly understood. This study investigated the effects of NaCl and Cd on the growth, oxidative stress and antioxidant enzyme activities of Z. rouxii after stress treatment for 24 h. Results showed that NaCl or Cd alone negatively affected the growth of Z. rouxii, but the growth-inhibiting effect of Cd on Z. rouxii was reduced in the presence of NaCl. Flow cytometry assay showed that under Cd stress, NaCl significantly reduced the production of reactive oxygen species(ROS) and cell death of Z. rouxii compared with those in the absence of NaCl. The activities of superoxide dismutase(SOD), catalase(CAT), and peroxidase(POD) of Z. rouxii were significantly enhanced by 2%–6% NaCl, which likely contributed to the high salt tolerance of Z. rouxii. The POD activity was inhibited by 20 mg L-1Cd while the SOD and CAT activities were enhanced by 8 mg L-1 Cd and inhibited by 20 mg L-1 or 50 mg L-1 Cd. The inhibitory effect of high-level Cd on the antioxidant enzyme activities of Z. rouxii was counteracted by the combined use of NaCl, especially at 6%. This probably accounted for the decrease in Cd-induced ROS production and cell death of Z. rouxii after incubation with NaCl and Cd. Our work provided physiological clues as to the use of Z. rouxii as a biosorbent for Cd removal from seawater and liquid highly salty food.

Construction of Overexpression Vector of ACBP Gene in Zygosaccharomyces rouxii

The Zygosaccharomyces rouxii is a kind of fermentation yeast which yield flavoring substance in the production of soy sauce. In order to the overexpression of the target protein in wild type strains, we choose PYEs2.0 as the original carrier, the acyl-coA binding protein (ACBP) and GFP gene have been cloned in the multiple cloning site. The screening of labeled URA3 gene was replaced by KanMX gene which anti G418. The vector was obtained through the screening of G418 at the concentration of 25 ug/ml.