Diversidade fenotípica e desempenho fermentativo de leveduras autóctones isoladas de variedades de cana-de-açúcar.

Abstract

The search for new yeast strains with superior technological characteristics plays an essential role in advancing fermentation biotechnology, particularly in improving industrial processes aimed at ethanol and fermented beverage production. In this context, the present study aimed to isolate, select, characterize, and evaluate the fermentative performance of autochthonous yeasts from different sugarcane varieties, with the goal of identifying strains with high biotechnological potential suitable for sustainable and high-efficiency production processes. The research was conducted using samples collected from the juice extracted from the upper and basal parts of ten sugarcane varieties cultivated at the Experimental Farm Chã do Jardim. Samples were stored in microtubes containing glycerol and maintained in an ultra-freezer at - 80 °C until analysis. The yeasts were reactivated, purified by successive streaking, and morphologically characterized. Subsequently, they were subjected to tolerance and performance tests under various conditions, including temperature variation (4 °C, 15 °C, 20 °C, 30 °C, and 40 °C), assimilation of different carbon and nitrogen sources, resistance to ethanol and acetic acid, hydrogen sulfide (H2S) production, as well as evaluations of fermentative performance, cell viability, and post-fermentation flocculation. All analyses were performed in duplicate. For data processing, Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) were applied, using standardization and Euclidean distances to identify similarity patterns among the strains. The results revealed wide metabolic variability among the isolated yeasts. Strains FYFSS-1 and FYFSI-1 exhibited high growth

rates at all tested temperatures, indicating strong thermal tolerance and potential for use in non- alcoholic fermentations. Strains FYFSS-5, FYFSS-2, and FYFSI-8 showed the highest

productivity (Px), fermentation rate (V), and product yield per substrate (YP/S), making them ideal for high-ethanol-yield processes. Meanwhile, strains FYFSS-3, FYFSS-5, FYFSS-7, and FYFSI-2 displayed higher specific ethanol formation rates (qp) and greater CO2 release, suggesting their suitability for intensive fermentation processes. Conversely, strains FYFSS-1, FYFSS-10, FYFSI-1, and FYFSI-7 presented slower fermentation rates, correlating with higher residual sugar content and total acidity. Finally, FYFSS-4, FYFSS-6, FYFSS-9, FYFSI-3, FYFSI-4, FYFSI-6, FYFSI-9, and FYFSI-10 demonstrated increased biomass yield. The HCA analysis grouped the strains into five distinct clusters, reflecting their metabolic and technological diversity. In conclusion, the isolated autochthonous yeasts exhibit significant and diverse biotechnological potential, making them applicable to various industrial contexts. The identification of strains with high thermal tolerance, enhanced ethanol productivity, and differentiated growth capacities contributes to the development of more efficient, sustainable, and regionally adapted fermentation processes for sugarcane-based industries.