Immobilization of Thermoalkalophilic Lipase from Bacillus atrophaeus FSHM2 on Amine-Modified Graphene Oxide Nanostructures: Statistical Optimization and Its Application for Pentyl Valerate Synthesis

Abstract

Synthesis of (3-aminopropyl) triethoxysilane (APTES)-functionalized graphene oxide (GO) nanosheets, statistical optimization of conditions for immobilization of Bacillus atrophaeus lipase (BaL) on as-synthesized support, and application of the immobilized BaL for esterification of valeric acid were carried out in this investigation. The optimum specific activity of the immobilized BaL (81.60 ± 0.28 U mg�1) was achieved at 3 mg mL�1 of GO-NH2, 50 mM of phosphate buffer, pH 7.0, 60 min sonication time, 100 mM glutaraldehyde, 25 U mL�1 of enzyme, and 8 h immobilization time at 4 °C. The immobilized BaL retained about 90 of its initial activity after 10 days of storage. Moreover, about 70 of the initial activity of the immobilized BaL was retained after 10 cycles of application. The results of esterification studies exhibited that maximum pentyl valerate synthesis using the free BaL (34.5) and the immobilized BaL (92.7) occurred in the organic solvent medium (xylene) after 48 h of incubation at 60 °C. © 2019, Springer Science+Business Media, LLC, part of Springer Nature