Perfil de tolerancia a variaciones de acidez y etanol de bacterias aisladas de la fermentación alcohólica en una planta productora de azúcar y bioetanol de araras SP-BRASIL.

Abstract

The tolerance of bacteria isolated from the industrial bioethanol fermentation process to acid-ethanol stress conditions was evaluated, with the aim of characterizing their response to different pH levels (6.0, 5.5, 4.5, 3, 5 and 2.5) and ethanol concentrations (0%, 5%, 10%, 15% and 20%). To determine their tolerance profiles, an absorbance variation analysis (ΔAbs) was carried out; heat maps were used to visualize and compare the behavior of the inmates and the Tukey test was used to determine differences in the individual responses of each isolate. Furthermore, a heat map with hierarchical clustering was generated using the Euclidean distance and the complete linkage method, to classify the bacteria according to their stress response. The results will reveal significant diversity in bacterial tolerance profiles. Bacteria isolated from collection 1, such as C1B3 and C1B2, stood out for their high tolerance to ethanol concentrations of up to 20%, while C6B2, from collection 6, demonstrated exceptional tolerance to an extremely low pH (2.5). These isolates showed outstanding growth drivers, in some cases surpassing the collection strains evaluated as points referring to Lactobacillus fermentum and Lactobacillus plantarum. A general trend of greater sensitivity to acidic pH than to ethanol has been observed, indicating that acid stress is a key limiting factor in these systems. Differentiated metabolic strategies were identified among the isolates. Some bacteria presented prolonged dormancy phases followed by robust growth, while others, with a rapid onset of growth, showed less long-term sustainability. This study highlights the complexity of bacterial dynamics in industrial environments, underlining the importance of continuing to investigate the resistance and adaptation mechanisms of these bacteria.