Ionic liquids as novel solvents for biosynthesis of octenyl succinic anhydride-modified waxy maize starch

• Starch was pre-gelatinized in [BMIm]Cl and bio-esterified with OSA in [OMIm]NO3.
• [BMIm]Cl was excellent solvent for starch dissolution.
• Ionic liquid was confirmed to be feasible solvent for starch bio-modification.
• Bio-esterification conditions were optimized.

Biosynthesis of octenyl succinic anhydride (OSA) starch was investigated using ionic liquids (ILs) as reaction media. Waxy maize starch was pretreated in 1-butyl-3-methylimidazolium chlorine and then esterified with OSA in 1-octyl-3-methylimidazolium nitrate by using Novozyme 435 as catalyst. The degree of substitution of OSA starch reached 0.0130 with 5 wt% starch concentration and 1 wt% lipase dosage based on ILs weight at 50 °C for 3 h. The formation of OSA starch was confirmed by fourier transform infrared spectroscopy. Scanning electron microscopy and X-ray diffraction revealed that the morphology and crystal structure of starch were significantly destroyed. Thermogravimetric analysis showed that esterification decreased the thermal stability of starch. The successful lipase-catalyzed synthesis of OSA starch in ILs suggests that ILs are potential replacement of traditional organic solvents for starch ester biosynthesis.

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