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.

Enhancing antioxidant activity and fragrant profile of low-ethanol kiwi wine via sequential culture of indigenous Zygosaccharomyces rouxii and Saccharomyces cerevisiae

To explore a novel producing strategy for enhancing antioxidant activity and aroma of low-ethanol kiwi wine,kiwifruit juice was sequential fermentation with indigenous Zygosaccharomyces rouxii(Zr)and Saccharomyces cerevisiae(Sc)without adding sugars.The organic acids,bioactive compounds,volatile constituents,antioxidant capacities and sensory profiles were measured to evaluate the performance of different inoculation ratios.The results indicated that compared with pure fermentation of Sc,the sequential fermentations significantly increased the total flavonoids,total phenols,some mono-phenols and antioxidant activities of the low-ethanol kiwi wines,and resulted in a positive effect on organic acids mainly by reducing the content of malic acid.At the same time,sequential fermentations significantly enhanced the aroma profile of the low-ethanol kiwi wines.The higher inoculation ratio of Zr greatly increased the complexity of the volatiles,improving sweet odor of the wines.While the similar inoculation ratio of Zr and Sc significantly increased the volatile contents,intensifying the tropical fruity and kernel fruity.In addition,the partial least-squares regression analysis showed that aldehydes resulted in sourness,ethyl esters and acetate esters possessed a positive impact on tropical fruity and kernel fruity.

Effect of co-inoculation of different halophilic bacteria and yeast on the flavor of fermented soy sauce

The flavor of soy sauce is closely related to the succession and interaction of the microbial community during fermentation.In this study,the selected potential flavor-producing microorganisms(7 species of bacteria and 4 species of yeast)were applied in the co-culture rapid fermentation model and their growth,physicochemical changes,volatile flavor compounds(VFCs),and sensory characteristics were investigated.Results showed that yeast promoted the growth of bacteria,while bacteria inhibited the growth of yeast in the co-culture model.Based on the results of VFCs and sensory evaluation,the combined fermentation of Zygosaccharomyces rouxii and Lactobacillus fermentum was the best strategy out of the 40 combinations.The effect of this combination was also validated in a 20 L fermentation application of soy sauce,which indeed enhanced the intensity of sauce-like,fruity,smoky,and caramel-like notes,as well as umami and kokumi tastes.These results provide a theoretical basis for the exploration and industrial application of flavor-producing microorganisms in soy sauce fermentation.