Extraction and characterization of pectin methylesterase from muskmelon biowaste for pectin remodeling

Pectin methylesterase (PME) extracted from muskmelon was purified by anion exchange chromatography. The specific activity of purified enzyme was 152.01 U/mg and relative molecular weight was ~69,000 Da. Methylesterase was characterized for various physicochemical factors to designate its suitability in the food industry applications. The optimum temperature of the enzyme was 30°C and is thermally stable between the temperature ranges of 15-65°C with critical temperature for stability being >65°C. Thermal inactivation first order kinetics and thermodynamic parameters in temperature range (45-65°C) favors stability of PME and at 75°C complete inactivation of enzyme was observed indicating the unstable nature of enzyme over >65°C. Activation energy (E_a ) and Z values of thermal inactivation were found to be 100.108 kJ/mol and 2.05°C, respectively. About 0.1 M NaCl is essential for enzyme to attain the maximum activity. The enzyme lost activity in presence of divalent calcium (Ca²⁺ ) and magnesium (Mg²⁺ ) ions. PRACTICAL APPLICATIONS: Pectin methylesterase (EC3.1.1.11) are an important class of enzymes expressed in plants and microbes and they bring about the de-methylesterification on pectin substrate. Up to ~13% degree of esterification of pectin was observed with muskmelon PME enzyme treatment. The de-methylesterified pectin thus prepared was subjected for gelation in presence of Ca²⁺ ions and above 0.5% of demethylesterified pectin stable calcium pectate gels were produced. The study demonstrates the suitability of muskmelon PME extracted from biowaste in food applications with good gelling property.