A "green" method for the preparation of starch-g-poly(butyl acrylate) (starch-g-PBA) copolymers using a biocatalyst, horseradish peroxidase (HRP), in the presence of hydrogen peroxide (H2O2) and acetylacetone (Acac) was developed. The chemical structures and thermal properties of the grafted starch were analyzed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy(H-1 NMR), elemental analysis, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). FT-IR, elemental analysis, and H-1 NMR confirmed that PBA was successfully grafted onto starch by HRP-mediated graft copolymerization. DSC and TGA results showed that the grafting of PM chains improved the thermal stability of starch. The effects of grafting on the rheological properties of the Starch pastes were also studied. Compared to control starch, the grafted starch paste had higher viscosity and showed better elastic behavior. The effects of gelatinization and addition of ethanol on the graft copolymerization were also investigated. The results indicated that gelatinization and addition of ethanol improved the grafting percentage (GP, 5.66%) and grafting efficiency (GE, 19.39%). (C) 2017 Elsevier Ltd. All rights reserved.