Glycerol Bioconversion into Bioethanol: A Comparative Analysis of Microbial Growth and Structural Adaptation

Introduction Glycerol, the main byproduct of biodiesel production, poses environmental challenges if not effectively utilized. Converting glycerol into bioethanol provides a sustainable route to support renewable energy development. This study explores the potential of microbial isolates with high lipase activity for efficient glycerol fermentation. Methods The tested strains included three bacteria ( Serratia sp. , Pseudomonas sp. , Escherichia coli ), one yeast ( Saccharomyces sp. ), and two fungi ( Aspergillus sp. , Trichoderma sp. ). Morphological adaptations were evaluated using Scanning Electron Microscopy (SEM), and ethanol production was validated through Fourier-Transform Infrared (FT-IR) spectroscopy by identifying characteristic absorption peaks. Quantitative analysis of ethanol yield and glycerol conversion was conducted using High-Performance Liquid Chromatography (HPLC). Results SEM analysis confirmed structural adaptation of Serratia sp. and Saccharomyces sp. under fermentation stress. FT-IR analysis verified the presence of ethanol with an absorption peak at 3251.52 cm −1 . HPLC results showed that Serratia sp. produced the highest ethanol yield of 17.83% (5.35 g/L) with a glycerol conversion of 40.33%, followed by Trichoderma sp. with a yield of 17.37% (5.21 g/L) and a conversion of 39.56%. Although E. coli exhibited the highest glycerol conversion (80.54%), its ethanol yield was low (1.88%), indicating diversion toward other metabolic pathways. Discussion These results highlight the superior adaptability and metabolic efficiency of Serratia sp . in channeling glycerol toward ethanol production. Structural stability under osmotic and ethanol stress supports its role as a robust bioethanol producer, while differences among species underscore the importance of strain-specific optimization. Conclusion Serratia sp. demonstrates strong potential for glycerol-to-bioethanol conversion, providing a promising candidate for sustainable biofuel production and biodiesel waste valorization.