Breeding of High Yield β-glucosidase Yeast by Mutagenesis and Its Effect on the Aroma Characteristics of Rosa roxburghii Tratt Wine

To analyze the effects of β-glucosidase on the aroma characteristics of Rosa roxburghii Tratt (Rosa roxburghii) wine, a strain of Wickerhamomyces anomalus (W. anomalus) C4 producing β-glucosidase was used as the starting strain, and its β-glucosidase activity was further improved by mutagenesis using ethylmethanesulfonate (EMS). R. roxburghii wine was produced via pure or mixed inoculatation of W. anomalus or together with Saccharomyces cerevisiae. The β-glycosidase producing ability was examined using p-nitrophenyl-β-D-glucopyranoside colorimetry. Headspace solid phase microextraction (HS-SPME) and gas phase mass spectrometry (GC-MS) were performed to determine the volatile aroma substances of each group of R. roxburghii wine. A mutant strain W.anomalus E3 with stable β-glucosidase produced activity was obtained using the mutagenic agent EMS, and the enzyme activity of W.anomalus E3 was (55.05±1.74) U/L, which increased 31.70% compared with the starting strain W.anomalus C4. β-glucosidase activity increased gradually, reached its maximum at the 10th day, and then decreased rapidly during the fermentation process of R. roxburghii wine. Inoculation with W.anomalus C4 and E3 could reduce theacidity value including total acid, volatile acid and pH of the R. roxburghii wine, and the total sugar content was also decreased. Moreover, inoculation with W.anomalus C4 and E3 also regulate the aroma characteristics, such as increasing the volatile ester and alcohol content and the OAVs of the main aroma components. Therefore, it was helpful to regulate the aroma characteristics and increase the complexity and richness of the R. roxburghii wine when inoculation with W.anomalus strain producing β-glucosidase.