Lipase from Stenotrophomonas maltophilia strain HO5 for efficient biodiesel synthesis using non-edible plant oils.

The increasing global demand for sustainable and renewable energy has intensified interest in microbial lipases as efficient biocatalysts for biodiesel production. A lipase-producing bacterium isolated from waste-oil-contaminated environments was identified as Stenotrophomonas maltophilia strain HO5 through 16 S ribosomal RNA gene sequencing. The strain exhibited a maximum lipase production of 28 U mL⁻¹. The purified monomeric enzyme (approximately 55 kDa) showed a Michaelis constant (Km) of 1.728 mM and a maximum reaction velocity (Vmax) of 80 U mL⁻¹, indicating high catalytic efficiency. The enzyme retained 112.05% residual activity in the presence of ferric ions and 113.10% activity in methanol, while ethylenediaminetetraacetic acid caused strong inhibition (> 80%), suggesting partial metal ion dependence. The enzyme efficiently catalyzed the conversion of non-edible wild olive oil and taramira oil into biodiesel, confirmed by Fourier transform infrared spectroscopy through characteristic ester carbonyl stretching peaks. Gas chromatography-mass spectrometry analysis revealed fatty acid methyl esters ranging from C8 to C24. Wild olive oil biodiesel was dominated by methyl oleate (48.53%), followed by methyl linoleate (21.64%) and methyl palmitate (14.85%), whereas taramira oil biodiesel contained higher proportions of methyl linoleate (32.81%), methyl oleate (22.37%), and methyl erucate (18.72%). The predominance of unsaturated methyl esters confirms efficient enzymatic transesterification and highlights the catalytic robustness and industrial potential of this lipase for sustainable biodiesel production.