Impact of <i>Lachancea thermotolerans</i> strain and lactic acid concentration on <i>Oenococcus oeni</i> and malolactic fermentation in wine

Abstract

The yeast Lachancea thermotolerans can produce lactic acid during alcoholic fermentation (AF) and thereby acidify wines with insufficient acidity. However, little is known about the impact of L. thermotolerans on Oenococcus oeni, the primary lactic acid bacterium used in malolactic fermentation (MLF). This study explored the impact of sequential cultures of L. thermotolerans and Saccharomyces cerevisiae on MLF performance in white and red wines. Four L. thermotolerans strains were tested in Sauvignon blanc with sequential S. cerevisiae inoculation, compared to an S. cerevisiae control and the initially un-inoculated treatments. The L. thermotolerans wines showed large differences in acidification, and progression of MLF depended on lactic acid production, even at controlled pH. The highest and lowest lactic acid producing strains were tested further in Merlot fermentations with both co-inoculated and sequentially inoculated O. oeni. The low lactic acid producing strain enabled successful MLF, even when this failed in the S. cerevisiae treatment, with dramatically quicker malic acid depletion in O. oeni co-inoculation than in sequential inoculation. In contrast, a high lactic acid producing strain inhibited MLF irrespective of the O. oeni inoculation strategy. In a follow-up experiment, increasing concentrations of exogenously added lactic acid slowed MLF and reduced O. oeni growth across different matrices, with 6 g/L of lactic acid completely inhibiting MLF. The results confirm the inhibitory effect of lactic acid on O. oeni while highlighting the potential of some L. thermotolerans strains to promote MLF and the others to inhibit it.

An Integrative View of the Role of Lachancea thermotolerans in Wine Technology

“…The S. cerevisiae control produces 30% less glycerol than the sequential fermentations between Concerto and S. cerevisiae. Other studies have reported non-significant differences for the three studied commercial L. thermotolerans strains in sequential fermentations, while the S. cerevisiae control produces 15% less glycerol [15].…”

“…Recent studies have compared some of the different available commercial strains (Levulia TM , AEB, Italy; Concerto TM , CHR Hansen, Denmark; Laktia TM , Lallemand, Canada) [14][15][16], showing interesting differences and even contradictory results regarding several enological parameters, depending on the study. According to all of them, sequential fermentation using L. thermotolerans and S. cerevisiae is more efficient than co-inoculation as far as lactic acid production is concerned.…”

“…All sequential fermentations consume all of the fermentative sugars. Another study reported that the commercial L. thermotolerans strains (Laktia, Levulia, and Concerto) slightly reduce the final ethanol concentration in sequential fermentations by 0.475, 0.33%, and 0.16% (v/v), respectively, compared to the S. cerevisiae control [15]. Pure fermentations using Concerto reach an ethanol concentration of up to 8% (v/v), while Laktia ferments up to 6.2% (v/v) [16].…”

“…Today, there are seven strains from different manufacturers [13]. Two recent studies compare the three most popular available commercial strains [14,15], with an additional study comparing only two of them [16]. However, on some occasions, the results are contradictory, and the performance could depend on additional factors that are different from yeast strain parameters.…”

“…Some articles have studied new parameters, such as mannoproteins and polysaccharides production, in combinations of L. thermotolerans and Schizosaccharomyces pombe [18], achieving the desired microbial stabilization from a malic acid point of view directly after alcoholic fermentation while acidifying wine [19]. Recent works have studied combinations with O. oeni [15,20] in order to achieve microbial stability and to avoid difficult malolactic fermentations under difficult scenarios while acidifying wine. Other studies have investigated multistarters that include L. thermotolerans and other non-Saccharomyces strains such as Torulaspora delbrueckii in order to improve flavor and volatile compound composition [21].…”