Immobilization of lipase on the modified magnetic diatomite earth for effective methyl esterification of isoamyl alcohol to synthesize banana flavor.

The present study was designed to propose a simple, cost-effective, and efficient method for the preparation of a biocompatible composite made from magnetic diatomaceous earth (mDE) coated by aminopropyltriethoxysilane (APTES) and its application for immobilization of porcine pancreatic lipase (PPL). The produced mDE-APTES was instrumentally characterized and the obtained results of FTIR analysis and scanning electron microscopy equipped by energy-dispersive X-ray spectroscopy (SEM-EDS) showed successful coating of APTES on mDE surface. PPL was then immobilized onto mDE to obtain the biocatalyst of PPL@mDE (immobilization yield and efficiency of 78.0 ± 0.3% and 80.1 ± 0.6, respectively) and the presence of enzyme was confirmed by EDS method. The attained results of the reusability of PPL@mDE revealed that 57% of the initial activity was retained after 11 cycles of biocatalyst application. PPL@mDE demonstrated higher storage stability than the free enzyme at 4 °C, 25 °C, and 37 °C. The apparent Km (2.35 ± 0.12 mM) and Vmax (13.01 ± 0.64 µmol/min) values for the immobilized enzyme were considerably altered compared to those of the free enzyme (p > 0.05). PPL@mDE was subsequently employed for the synthesis of banana flavor (isoamyl acetate) in n-hexane, which yields an esterification percentage of 100 at 37 °C after 3 h. However, it merits further investigations to find out about large-scale application of the as-synthesized biocatalyst for esterification.