Influence of mixed fermentations with Starmerella bacillaris and Saccharomyces cerevisiae on malolactic fermentation by Lactobacillus plantarum and Oenococcus oeni in wines

Abstract

Over the last years, the potential use of non-Saccharomyces yeasts to modulate the production of target metabolites of oenological interest has been well recognized. Among non-Saccharomyces yeasts, Starmerella bacillaris (synonym Candida zemplinina) is considered one of the most promising species to satisfy modern market and consumers preferences due to its peculiar characteristic (enhance glycerol and total acidity contents and reduce ethanol production). Mixed fermentations using Starm. bacillaris and Saccharomyces cerevisiae starter cultures represent a way to modulate metabolites of enological interest, taking advantage of the phenotypic specificities of the former and the ability of the latter to complete the alcoholic fermentation. However, the consumption of nutrients by these species and their produced metabolites may inhibit or stimulate the growth (and malolactic activity) of lactic acid bacteria (LAB). Consequently, a comprehensive understanding of the interactions between yeasts and LAB would be valuable for an efficient implementation of malolactic fermentation (MLF). To this end, the present study was carried out to elucidate the impact of this inoculation protocol on the growth and malolactic activity of Lactobacillus plantarum and Oenococcus oeni strains used to induce MLF, and finally on the chemical and volatile profile of Nebbiolo wines. MLF was carried out by inoculating LAB at the beginning and at the end of the alcoholic fermentation. Yeast inoculation protocol and the combination of tested species influenced LAB population dynamics and malic acid consumption. MLF in which L. plantarum was inoculated at the beginning of the fermentation were completed faster than those inoculated with O. oeni. On the contrary, when L. plantarum was inoculated at the end of alcoholic fermentation a stuck MLF was observed, while O. oeni completed successfully MLF, indicating that inoculation timing of both LAB species was critical to how rapidly starts and finish the MLF. The presence of Starm. bacillaris in mixed fermentations promoted O. oeni growth and increased malic acid consumption rate. Analysis from volatile composition showed that LAB species selection had a greater impact to aroma profile of the wines than inoculation time. This knowledge could be useful to better control MLF in mixed fermentations with Starm. bacillaris and S. cerevisiae, and underlines the importance of the inoculated yeasts on the growth and malolactic activity of the LAB.