Sustainable biofuel production from fish processing waste: lipase-catalyzed hydroesterification of tilapia residual oil

Abstract

Fishing waste and byproducts, whether naturally occurring or from industrial processing, are important sources of high-value compounds. Fertilizers, biomaterials, cosmetics, biolubricants, and biodiesel are some of the substances that can be obtained from these residues. The objective of this study was to conduct a theoretical and experimental investigation of the biocatalytic production of ethyl esters through the enzymatic hydroesterification of residual tilapia (Oreochromis niloticus) oil. Eversa Transform 2.0 lipase was used during the esterification stage, with the Taguchi methodology applied to assess the effects of varying parameters: temperature (25, 40, and 55 °C), molar ratio of free fatty acids (FFA) to ethanol (1:1, 1:5, and 1:9), biocatalyst concentration (1%, 5%, and 9%), and reaction time (1, 3, and 5 h). Statistical analysis revealed that the amount of biocatalyst was the most significant factor, followed by temperature. The optimal levels identified were 5 h of reaction at 25 °C, with a 1:1 (FFA/ethanol) molar ratio and 9% biocatalyst, resulting in an experimental conversion of 89.94 ± 0.09%. A docking and molecular dynamics study was also conducted, evaluating the stability of Eversa Transform 2.0 lipase with FFAs, and the coupling of the enzyme’s catalytic site with the substrate was observed. Myristic and oleic acids bound near the enzyme’s active site, exhibiting favorable free energy and forming hydrogen bonds, alkyl interactions, and π-alkyl interactions, as revealed by an in silico study. This research aligns with key Sustainable Development Goals (SDGs), including SDG 7 (Affordable and Clean Energy) and SDG 9 (Industry, Innovation, and Infrastructure), and SDG 12 (Responsible Consumption and Production), by fostering the use of renewable energy and supporting more sustainable industrial processes.