A new understanding: Gene expression, cell characteristic and antioxidant enzymes of Zygosaccharomyces rouxii under the D-fructose regulation

Abstract Zygosaccharomyces rouxii is a well-known salt-tolerant yeast. In our previous study, it was interesting that Z. rouxii could produce higher levels of 4-hydroxy-2, 5-dimethyl-3(2 H)-furanone in 120 g/L D-fructose and 180 g/L NaCl involved YPD medium at 5 d. In order to explore the resistance and furanone production mechanisms of Z. rouxii under D-fructose regulation, a comparative transcriptomics method in Z. rouxii was to set to find differentially expressed genes, the physiological and biochemical indexes (growth and cell morphology, lipid peroxidation and relative electrical conductivity, the antioxidant enzymes activity), and the expression of oxidoreductase activity genes. The results indicated that a larger number of different expressed genes at transcriptome analysis, such as the series antioxidant enzymes were related to the resistance characteristics. Research had confirmed that the living cell numbers and cell areas of D-fructose regulation group were significantly lower than the controls at the initial stage, while those higher than of the controls at the late stage. During the fermentation period, the lipid peroxidation and the relative electrical conductivity of the yeast cell membrane were increased. And also the D-fructose regulation group present lower inhibition superoxide anion ability. The activity of CAT in the D-fructose regulation group was always higher than that of the control group. Only the activity of GSH-Px was found to be significantly increased at 1 d except for other enzymes activities. Most of the oxidoreductase activity genes, such as especially the GSH-Px gene under D-fructose regulation conditions were expressed at higher levels than those of control groups. Combining the levels of transcription and enzymes activity data, those could understand that exogenous D-fructose had a stress effect on Z. rouxii at the early stage of culture. With the fermentation time progress, it was no longer a stressor substance for the Z. rouxii, and changed the nutrient to promote growth of Z. rouxii in the later stages. During the whole process, GSH-Px was the main defense enzyme and CAT was the sustained defense enzyme. Therefore, the experimental results might provide effective mechanisms in Z. rouxii for practical application of furanone production in the industry under exogenous D-fructose regulation.