Enhanced lipase production from ionic liquid tolerant Klebsiella aerogenes using mustard oilcake for efficient biodiesel production

Lipase production was achieved using a thermo-alkalophilic-halophilic-ionic liquid-tolerant strain of Klebsiella aerogenes IBGE-ASQ-AA-BC-004, with mustard oilcake serving as the substrate. This production holds significance for various biotechnological applications, particularly in biodiesel and detergent manufacturing. Notably, the bacterium demonstrated lipase production containing 15 % w w⁻¹ of various ionic liquids, showcasing its resilience and adaptability to adverse chemical conditions—crucial attributes for industrial utilization. Several experiments were designed to optimize the lipase production conditions, revealing rice bran as the most effective carbon source among the tested untreated agricultural residues. Ionic liquid pretreatment not only facilitated bacterial growth but also enhanced lipase production, indicating a synergistic effect. Supplementing mineral medium with oilcakes from various oils, notably mustard oilcake, significantly promoted bacterial growth and increased lipase production. Addition of Tween 20 and polyethylene glycol surfactants substantially boosted lipase production, potentially enhancing enzyme stability and substrate accessibility. The stability of the purified lipase was assessed under various conditions to determine its thermostability, alkalophilic nature, and tolerance to ionic liquids. These properties were evaluated by incubating the enzyme under different temperatures ranging from 25 to 80 °C for 24 h to assess thermostability, varying pH values from 4 to 12 for 24 h to determine alkalophilic behavior, and exposure to 20 % (w v⁻¹) ionic liquids for 24 h to establish tolerance. The produced lipase was subjected to the transesterification of waste cooking oil, yielding 83.21 % fatty acid methyl ester after 24 h. This high yield demonstrates the effectiveness of the optimized lipase in biodiesel production, contributing to sustainable energy production by utilizing waste and renewable resources.