CHARACTERIZATION OF Starmerella magnoliae STRAINS ISOLATED FROM PATAGONIAN MEAD.

VICTORIA KLEINJAN; GONZÁLEZ FLORES, MELISA; ORIGONE, ANDREA CECILIA; RODRIGUEZ MARIA EUGENIA; LOPES CHRISTIAN ARIEL

Los Cocos- Cordoba

Congreso; XVII Congreso Argentino de Microbiología General; 2022

SAMIGE

Cider production is focused in North Patagonia, Argentina (85% of national production) as it is the most important producing region of seed fruit (apples and pears). Apple and pear must usually present higher fructose than glucose concentrations. During alcoholic fermentation, Saccharomyces cerevisiae, the yeast conventionally used, has glucose affinity and produces beverages with high fructose residue. Recently, the fructophilic yeasts, Starmerella magnoliae (Sm) have been isolated from Patagonian honey. There are a limited number of studies that evaluate the potential of this species to be used as fermentative yeasts for musts with abundant fructose.In this study, a physiological characterization of different strains of Sm isolated from the honey of Neuquén province was carried out to evaluate the main characteristics of interest for the fermented beverage industry.A total of 28 Sm isolates from honey collected in 8 regions of Neuquén were obtained. From these isolates, 3 different strains, coexisting in the sampled regions, were found by mtDNA-RFLP: 15 strains with profile A, 12 with B, and 1 with C. 5 and 4 isolates of strains A and B, respectively, and the one with profile C (NPCC1782) were selected for their study under different conditions of temperature, tolerance to sulfite, and ethanol.Growth profile at different temperatures (8,13,20,30 and 37°C) 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.Sulfite tolerance was evaluated by drop assay in YEPD-agar with 0.075M tartaric acid, using increasing concentrations of Na2S2O5 (0,1,2,3 and 4mM). Most isolates grew up to a concentration of 4mM (about 500mg/L total SO2), this behavior was similar to the T73t strain of S. cerevisiae (used as control). Only NPCC1782 (profile C) showed tolerance up to 2mM (250mg/L SO2), being appropriate to carry out apple or pear must fermentation in cidermaking industry.Finally, the kinetic parameters of these strains were evaluated by monitoring OD640nm in Elisa plates containing YNB with increasing concentrations of ethanol (0,2,3,5,7 and 8% v/v). All strains were able to grow up to 8% ethanol. However, NPCC1782 presented the highest µ (maximum growth rate) and the lowest lag (time to start vigorous fermentation) at 8%. In addition, strains from group B had intermediate kinetics, while those of profile A showed decreased kinetics at 8% compared to the others.