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

This is the authors' abstract. We don't add key points for this paper.

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.