lipase-catalyzed green synthesis of starch–maleate monoesters and its characterization

The present study reports the green synthesis of starch–maleate (sm) at ambient temperature in solvent-free system using rhizopus arrhizus lipase as a biocatalyst and maleic acid (ma) as an esterification agent. the synthetic scheme was found to be efficient, economical, and ecofriendly. the newly synthesized sm samples were characterized using fourier transform infrared (ftir) and proton nuclear magnetic resonance (1h nmr) spectroscopic techniques. the degree of substitution (ds) was found in the range of 0.53–0.62. moreover, ds was found to be temperature and time-dependent. x-ray diffraction (xrd) exhibited that maleation did not change the crystalline nature of native starch. scanning electron microscopy (sem) revealed that size of sm granules was in the range of 4–18 µm. the activation energy (ea) of sm formation was calculated to be 42.94 kcal mol−1 which clearly indicated the effective and rapid interaction of functional groups. hence, the solvent-free solid-state synthetic methodology proved to be excellent for the synthesis of novel biomaterials with appreciable high ds for drug delivery and sorption of heavy metal ions from water.