Purification and characterisation of an acidic pectin lyase produced by Aspergillus ficuum strain MTCC 7591 suitable for clarification of fruit juices

An acidic pectin lyase (E.C 4.2.2.10) produced by Aspergillus ficuum MTCC 7591 of molecular weight 31.6 kD was purified to apparent homogeneity by ion exchange and gel filtration chromatography. Eighty-six fold purification with 60% yield and a specific activity of 7.8 U/mg protein was obtained. The Km and calculated turnover number (kcat) of the purified enzyme were found to be 0.60 mg/ml and 74 s(-1) respectively using citrus pectin as the substrate. The pH and temperature optima were 5.0 and 50 degrees C respectively. Exposed to 24 hours at a particular pH the enzyme was found to be relatively stable in the pH range 2.0-9.0. Exposed to a particular temperature for 1 hour, the enzyme retains full activity up to 40 degrees C. Metal ions and protein inhibitors did not have significant effects on the activity of the enzyme. The enzyme has been found to be very effective in the clarification of sweet lime and orange juices.