Synthesis of geranyl propionate in a solvent-free medium using Rhizomucor miehei lipase covalently immobilized on chitosan-graphene oxide beads

The chemical route of producing geranyl propionate involves the use of toxic chemicals, liberation of unwanted by-products as well as problematic separation process. In view of such problems, the use of Rhizomucor miehei lipase (RML) covalently bound onto activated chitosan–graphene oxide (RML-CS/GO) support is suggested. Following analyses using Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetry, properties of the RML-CS/GO were characterized. A response surface methodological approach using a 3-level-four-factor (incubation time, temperature, substrate molar ratio, and stirring rate) Box–Behnken design was used to optimize the experimental conditions to maximize the yield of geranyl propionate. Results revealed that 76 ± 0.02% of recovered protein had yielded 7.2 ± 0.04 mg g−1 and 211 ± 0.3% U g−1 of the maximum protein loading and esterification activity, respectively. The actual yield of geranyl propionate (49.46%) closely agreed with the predicted value (49.97%) under optimum reaction conditions (temperature: 37.67°C, incubation time: 10.20 hr, molar ratio (propionic acid:geraniol): 1:3.28, and stirring rate: 100.70 rpm) and hence, verifying the suitability of this approach. Since the method is performed under mild conditions, the RML-CS/GO biocatalyst may prove to be an environmentally benign alternative for producing satisfactory yield of geranyl propionate