Isolation and activity determination of enzymes secreted by aspergillus niger

Enzymes are being used in most processes in industries such as textile, leather, beer brewing, and fruit juice extraction. The advantages of using enzymes in place of chemicals include safety, reduction in energy costs, and reduction in pollution. However the use of enzymes in Zimbabwe is limited due to the high cost of importing them. Interestingly, these enzymes are generally produced by many microorganisms such as fungi and bacteria, so if they are isolated, they may be of use in different industries. Thus, this study focused on isolation and activity determination of pectinases and amylases secreted by the fungi Aspergillus niger. A. niger was resuscitated on potato dextrose agar and then subcultured in medium specific for the production of each targeted enzyme. Cells were centrifuged and the filtrate was expected to contain the crude enzyme. Specific substrates were used for the determination of the isolated enzyme's activity. The enzyme activity was determined spectrophotometrically by reading absorbance of the product formed in the presence of an enzyme and its specific substrate. Further work on enzyme activity determination was done by varying temperature, enzyme concentration, and substrate concentration. Results showed that the isolated amylase and pectinase had activity of 3.22 nkat/ml and 1.043 U, respectively. Optimum temperatures for these enzymes were 37°C for pectinase and 45°C for amylase. Thus, isolation of pectinases and amylases was successful; however, there is a need to induce the production and purify these enzymes for industrial use.