Assessment of β-D-glucosidase activity and bgl gene expression of Oenococcus oeni SD-2a.

Fan Wang,Wujun Ma,Jianzhong Zhou,Hongzhi Zhang,Xiaoli Liu,Yahui Li,Linlin Fan,Ying Wang

doi:10.1371/journal.pone.0240484

Fan Wang, Wujun Ma + Show 6 more

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https://doi.org/10.1371/journal.pone.0240484

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Abstract

Glycosidases enhance flavor during wine-making by mediating the enzymatic release of aroma molecules. In order to better understand the aroma enhancement potential of Oenococcus oeni SD-2a, β-D-glucosidase (βG) activities in the culture supernatant, whole cells, and disrupted cell lysate were assessed at mid log, late log and stationary growth phase. The enzymatic activity was also compared further from cell cultures with 5 different carbon sources (glucose, cellobiose, arbutin, glucose and cellobiose, glucose and arbutin) at late log phase. Correspondingly, expression levels of 3 bgl genes, OEOE-0224, OEOE-1210, and OEOE-1569 were investigated from cell cultures of the 3 growth phases, and the 5 cell cultures with different carbon sources. Finally, the volatile aroma compounds released by O. oeni SD-2a in synthetic wines with natural glycosides were evaluated by GC-MS. Results showed βG of O. oeni SD-2a was not extracellular enzyme, and the location of it didn’t change with the change of growth phase and carbon source studied. βG activities in the whole cells and disrupted cell lysate were similar and constant at the 3 growth phases. As for the carbon sources, βG activities of whole cells and disrupted lysate were positively affected by cellobiose. While arbutin displayed positive and negative effect on βG activity of whole cells and disrupted lysate, respectively. It is probably that bgl genes OEOE-0224 and OEOE-1210 were related to βG activity of SD-2a whole cells, while OEOE-1569 was responsible for βG activity of disrupted lysate. More kinds of volatile compounds and higher total concentration were released by SD-2a in synthetic wine compared with control. Thus, SD-2a showed a great potential for flavor enhancement under wine-like conditions. This study provides more information for further study of βG activity from O. oeni SD-2a.

Highlights

Most white wines and almost all red wines undergo a secondary fermentation, or malolactic fermentation (MLF), a process in which dicarboxylic L-malic acid is decarboxylated into monocarboxylic L-lactic acid [1,2]
Enzyme assay at different growth phases βG activities in culture supernatant, whole cells, and disrupted lysate of O. oeni SD-2a were assessed at mid log (48h), late log (80h), and stationary phase (98h) of growth
Obvious βG activities were detected in culture supernatant with the carbon source containing arbutin, while fairly low activities with glucose, cellobiose and their mixture

Summary

Introduction

Most white wines and almost all red wines undergo a secondary fermentation, or malolactic fermentation (MLF), a process in which dicarboxylic L-malic acid is decarboxylated into monocarboxylic L-lactic acid [1,2]. This bioconversion is carried out by lactic acid bacteria (LAB), especially by Oenococcus oeni the predominant LAB to conduct MLF [3]. In addition to decreasing wine sourness and increasing wine microbial stability via the metabolism of L-.

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