Extraction, partial purification and characterization of pectinases isolated from Aspergillus species cultured on mango (Mangifera indica) peels

Pectinase was produced from a culture of Aspergillus niger, Aspergillus fumigatus and Aspergillus flavus. Pectinase synthesis was achieved using mango (Mangifera indica) pectin extract as an inducer during pectinolytic fungi isolation while submerged fermentation process was carried out using ground mango peels as the sole carbon source. Substrate fermentation was evaluated within seven days by monitoring the pectinase activity every 24 h. The highest pectinase secretion was obtained from A. niger and A. fumigatus after 92 h (day 4) of incubation, while in A. flavus, it was after 120 h (day 5). Crude enzyme extracts from the three organisms were partially purified by a combination of ammonium sulphate precipitation and dialysis with an approximately two-fold purification of the pectinase and a yield of 5.4, 7.66 and 5.99% for A. niger, A. fumigatus and A. flavus, respectively after dialysis. The specific activities of 1.62, 1.79 and 1.86 U/mg for A. niger, A. fumigatus and A. flavus enzymes were calculated, respectively. Pectinase from A. niger and A. fumigatus had pH and temperature optima of 5.0 and 40°C, respectively, while that from A. flavus had pH and temperature optima of 5.0 and 45°C. The Michealis constant, Km and the maximum velocity, Vmax determined from Lineweaver-Burk plots of initial velocity data at different concentrations of the mango pectin extract were 0.357 mg/ml and 35.34 U; 0.156 mg/ml and 68.0 U; and 0.261 mg/ml and 60.61 U; for the enzymes from A. niger, A. fumigatus and A. flavus, respectively. The results suggest that mango peels can be used for value added synthesis of pectinase, an important enzyme with numerous biotechnological applications.Keywords: Mango peels, mango pectin extract, pectinase, Aspergillus niger, Aspergillus fumigatus, Aspergillus flavus, submerged fermentation, partial purification, characterization.African Journal of Biotechnology, Vol 13(24) 2445-242

Production and Partial Characterization of Cellulases from Apergillus fumigatus Using Two Distinct Parts of Corn Cob as Carbon Sources

Corn cobs were sun-dried for three days and separated into the hard outer part (Corn Cob Outer, CCO) and the soft inner part (the pulp) (Corn Cob Inner, CCI). Each part was milled separately. Aspergillus fumigatus isolated from sewage water was grown on and adapted to each part of corn cob. Using CCI and CCO, as the sole carbon sources for submerged fermentation, the organism produced cellulase. Activity was highest on the 3rd and 4th days using CCI and CCO, respectively. The crude cellulases were partially purified by 50% ammonium sulphate precipitation followed by dialysis. The partially purified cellulases were then characterized with respect to pH, Temperature and Themostability. While the optimum pH of the CCI cellulose was 6.0, that of CCO cellulase was pH 7.0. The optimum temperature of CCI was 55°C whereas that of CCO was 50°C. The stability of enzymes from 35°C to 70°C was studied. At 70°C, CCO cellulase has lost 45.88% of its original activity while CCI cellulase lost 58.14%. The results show that corn cob could serve as a cheap carbon source for the production of fungi cellulase. The study indicates that waste could be converted to wealth.Key words: Corn cob, cellulose, Aspergillus fumigates, submerged fermentation, partial purification