GCB Bioenergy_Figures_2024.xlsx

This study aimed to isolate, purify, and characterize a lipase from the gut symbiont <i>Bacillus megaterium </i>F25 (GenBank accession: MF597792) of the aquatic insect<b> </b><i>Rhantus suturalis,</i> with a focus its potential applications in biodiesel and food industries. Under optimized culture conditions, <i>B. megaterium </i>F25 could produce 583U/L of lipase in shaking flask culture. The purified lipase (PL) exhibited a specific activity with 113.89 U/mg and its molecular weight was determined as 34 kDa. The activity of PL was enhanced by methanol, ethanol, Tween-80, Triton X-100, Ca2+ and Mg2+, while β-mercaptoethanol, EDTA, SDS, Fe2+, Mn2+ and Cu2+ were inhibitory. PL showed optimal activity and stability at neutral and slightly acidic pHs, as well as in a temperature range of 20-30ºC. PL displayed strong hydrolytic activity towards plant oils and animal fats, indicating its potency for both food industry and the remediation of oil-contaminated environments. When tested as a catalyst, PL provided biodiesel production with a transesterification yield of 86.8% under optimized conditions (36 h reaction time, 4 mL enzyme solution, 30°C, pH 7.0 and waste-cooking oil:methanol ratio of 10 mL/40 mL). This is the first report on lipase-producing potential of gut microbial symbionts of aquatic insects. Furthermore, <i>B. megaterium</i> lipase was tested for the first time as a biocatalyst for biodiesel production.