Characterization of Starmerella magnoliae strains isolated from patagonian mead

VICTORIA KLEINJAN; MELISA GONZÁLEZ FLORES; ANDREA C. ORIGONE; M. EUGENIA RODRÍGUEZ; CHRISTIAN A. LOPES

Los Cocos, Córdoba

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Sociedad Argentina de Microbiología General - SAMIGE

In this study, a molecular and physiological characterization of a total of 28 isolates of S. magnoliae from 8 regions of Neuquén was carried out. Three different strains, coexisting in the sampled regions, were found according to their mtDNA-RFLP patterns: 15 isolates showing pattern A, 12 with pattern B, and 1 with pattern C. Isolates representatives from each particular pattern were selected under different stress conditions including temperature (8, 13, 20, 30 and 37°C), sulphite tolerance (0, 1, 2, 3 and 4 mM) and ethanol resistance (0, 2, 3, 5, 7 and 8% v/v). Growth profile at different temperatures was studied by drop assay on GPY-agar. All isolates grew in a range from 8°C to 30°C. However, the strains belonging to profile B grew at 37°C after 144h of incubation, with the NPCC1785 strain being the most thermotolerant. Sulphite tolerance was also evaluated by drop assay but using YEPD-agar with 0.075M tartaric acid and increasing concentrations of Na2S2O5. Most isolates (strains A and B) were able to grow up to a concentration of 4mM (about 500mg/L total SO2), a similar behavior observed for the positive control (T73t strain of S. cerevisiae). The only isolate representative of pattern C (strain NPCC1782) showed the lowest tolerance to this antimicrobial compound (2mM or 250mg/L SO2).Finally, the kinetic parameters of these strains were evaluated by monitoring OD640nm in 96 well microtiter plates containing YNB with increasing concentrations of ethanol. All strains were able to grow up to 8% v/v ethanol. Nevertheless, the strain NPCC1782 showed the highest μmax (maximum growth rate) and the lowest lag (time to start vigorous fermentation) at 8% v/v. In addition, strains showing pattern B evidenced an intermediate kinetics, while those of pattern A showed decreased kinetics at 8% compared to the others. These results indicate that all the evaluated S. magnoliae strains showed interesting properties to be used as putative starter cultures in low alcohol beverages, including high sulphite tolerance, ethanol resistance and a brad temperature growth range. Additional experiments about the fermentative performance are being carried out in order to complete the physiological characterization of this biotechnologically interesting yeast.