Production, purification and immobilization of pectinase from Aspergillus ibericus onto functionalized nanoporous activated carbon (FNAC) and its application on treatment of pectin containing wastewater

• The citrus pectin obtained from citrus peels were used as a substrate for the production of pectinase.
• Optimization of pectinase production conditions was analyzed using RSM.
• The maximum activity of pectinase was observed 69 U mL−1 by A. ibericus it is 2 folds higher than other reports.
• The purified pectinase was immobilized onto FNAC and increased stability of enzyme were seen.
• The PIFNAC was packed on column reactor for the treatment of pectin containing citrus processing wastewater.

The fungal strain Aspergillus ibericus was isolated from food waste for the production of pectinase. In this study response surface methodology (RSM) was employed to determine optimum conditions for the production of pectinase from citrus pectin. The optimum conditions for the production of pectinase were found to be pH, 4.0; temperature, 40 °C; incubation time, 120 h and substrate concentration (Citrus Pectin), 2% (w/v). The maximum activity of pectinase at optimum conditions was found to be 69.9 U mL−1. The purification by DEAE-Cellulose increased the specific activity of pectinase by about 10.1 fold from 64 to 650 U mg−1 protein. The molecular weight of the purified pectinase was found to be 41 kDa and 43 kDa. The purified pectinase was immobilized onto functionalized nanoporous activated carbon (FNAC), the maximum immobilization capacity of pectinase onto FNAC was found to be 3360 U g−1 at optimum immobilization conditions; time, 150 min; pH, 5.0; temperature, 35 °C and initial concentration of pectinase, 52 × 103 U (80 mg) L−1. The immobilized pectinase showed better thermal and storage stability than free pectinase. The immobilization of pectinase onto FNAC obeyed the Freundlich isotherm model. The immobilization of pectinase onto FNAC was confirmed by FT-IR, XRD, TGA, DSC and SEM analyses. The pectinase immobilized FNAC packed bed column reactor was used for the treatment of pectin containing wastewater under continuous mode. The maximum treatment efficiency for citrus pectin in synthetic wastewater was observed to be 82% at operating conditions: Hydraulic retention time, 180 min; pH, 5.0 and citrus pectin concentration 1% (w/v). Further, the citrus processing industrial wastewater was treated in pectinase immobilized FNAC packed bed column reactor and the system showed 94% of pectin treatment. The treatment of pectin in wastewater obeyed pseudo second order rate kinetic treatment model. The treatment of pectin in wastewater was confirmed by UV–vis spectroscopy and FT-IR spectrophotometer analyses.

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