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.