Non-covalent interaction between ferulic acid and arabinan-rich pectic polysaccharide from rapeseed meal

The sorption capacity of arabinan-rich pectic polysaccharide (ARPP) onto ferulic acid (FA) was investigated using equilibrium dialysis assays. UV and FT-IR spectra showed that FA was successfully adsorbed by ARPP. The effects of temperature, pH, buffer concentration, NaCl, and ethanol on sorption were investigated. Sorption variable optimization was examined by response surface methodology. The order of influence of each factor in affecting the sorption capacity was temperature > pH > buffer concentration. The maximum sorption yield was 363.92 ± 18.37 μg/mg at 36.8 °C, pH 5.26, and a buffer concentration of 0.09 M. Langmuir, Freundlich, and Temkin models were used to fit the experimental data under the optimized conditions. The Freundlich model showed the closest fit with an R2 of 0.995 and a △q% of 6.44. Scatchard plots of FA binding to ARPP indicated the existence of two types of binding sites, Type-1 and Type-2, which followed the Freundlich model. Significant decreases in the sorption of FA at elevated NaCl and ethanol concentrations indicated that hydrogen bonding and electrostatic forces involved in the sorption of FA onto ARPP.