Developing Solvent Tolerant Microbial Membranes: Lipid Extraction and Laurdan Fluorescence Approaches for Biofuel Optimization

Abstract

The high demand for sustainable energy has increased interest in advanced biofuels, though production is limited by solvent toxicity to microbial hosts. This study investigated the role of lipid composition in modulating membrane fluidity and solvent tolerance using Bacillus subtilis as a model organism. Five strains were cultured, and membrane lipids were extracted and analyzed using thin-layer chromatography and gas chromatography–mass spectrometry; however, inconsistent results limited compositional characterization. To address this problem, reconstituted vesicles composed of phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) were used as model membranes. Membrane fluidity was assessed using Laurdan fluorescence spectroscopy by measuring generalized polarization (GP) values across increasing 1‑butanol concentrations. Results showed a concentration-dependent decrease in GP, indicating increased membrane disorder. PG vesicles exhibited greater fluidization than PE:PG mixtures, demonstrating the stabilizing role of PE. These findings highlight the importance of lipid composition in membrane stability and suggest strategies to improve microbial robustness for biofuel production.