Bioprospecção de leveduras selvagens e imobilização em alginato de cálcio para produção de etanol.

Abstract

The primary objective of the present study was the isolation and characterisation of wild yeast strains derived from sugarcane juice cultivated in the municipality of Sumé, located in the semi-arid region of Paraíba, within the Caatinga biome. The study aimed to establish a microbial collection and to select strains exhibiting high fermentative productivity and ethanol tolerance, with a view to comparing their performance in free and immobilised fermentation systems. Between September 2023 and July 2024, a total of 30 wild yeast strains were isolated. Among these, those capable of producing over 5% (v/v) ethanol under laboratory conditions were of particular interest, with strain L-SO2C emerging as the most efficient, achieving ethanol production of 5.86%. The selected strains were subjected to ethanol tolerance assays, and their performance was benchmarked against that of the industrial strain JP1. Statistical analyses, conducted via ANOVA and Tukey’s test, revealed superior performance of strain L-SP1 in specific parameters. Strains L-SP1, L-SP2, and L-SO2C, along with strain JP1, were subsequently immobilised and physically characterised using Scanning Electron Microscopy (SEM). In terms of yield and productivity, strain JP1 demonstrated greater efficiency in the free-cell configuration after 96 hours of fermentation. Conversely, strains L-SO2C and L-SP2 outperformed in the immobilised system. Notably, L-SO2C exhibited the highest productivity within the initial six hours of fermentation (3.3 g/L·h), while L-SP2 showed consistent performance in both configurations, proving more effective under immobilised conditions. The use of immobilised configurations presented operational advantages, such as facilitating biomass separation from the final product4an aspect of industrial relevance due to its potential to reduce operational costs. Additionally, this approach offers enhanced protection to cells and mitigates issues related to substrate diffusion and microbial contamination. The findings underscore the high biotechnological potential of wild yeast strains isolated from sugarcane cultivated in the Caatinga for sustainable ethanol production. These results contribute to the valorisation of regional biodiversity as a strategic resource for industrial processes and to the advancement of biotechnology in the field of renewable biofuel production.