Bioprocessing of citrus waste peel for induced pectinase production by Aspergillus niger; its purification and characterization

Agro-industrial residues are primarily composed of complex polysaccharides that strengthen microbial growth for the production of industrially important enzymes. Pectinases are one of the most widely disseminated enzymes in bacteria, fungi and plants. Czapeck media supplemented with orange waste peel as carbon source under submerged fermentation process Aspergillus niger presenting the preeminent enzymatic production. On partial optimization culture showed the maximum enzyme yield (117.1 ± 3.4 μM/mL/min) at 30 °C in an orange waste peel medium having pH 5.5 and substrate concentration (4%) after 5th day of fermentation. The produced enzyme was purified by ammonium sulfate precipitation and ion exchange chromatography. A purification fold of 5.59 with specific activity and % recovery of 97.2 U/mg and 12.96% was achieved respectively after gel filtration chromatographic technique. The molecular weight of purified pectinase from A. niger was 30 kDa evidenced by SDS-PAGE. Pectinase activity profile showed purified enzyme was optimally active at pH = 7 and 55 °C. The maximum production of pectinase in the presence of cheaper substrate at low concentration makes the enzyme useful in industrial sectors especially for textile and juice industry.