Comparison of the kinetics and factors affecting the stabilities of chitin-immobilized naringinases from two fungal sources

Naringinases from both Penicillium sp. and Aspergillus niger were compared for their enzyme kinetics and the effects of sugars on the enzyme activities. Lineweaver-Burk plots showed that glucose, fructose and rhamnose were all competitive inhibitors for α-rhamnosidase of naringinase from Penicillium sp. and non-competitive inhibitors for the same enzyme from A. niger, When naringinase from Penicillium sp. was immobilized on chitin and used successively for the hydrolysis of p-nitrophenyl-α-rhamnoside or naringin in a simulated fruit juice system or grapefruit juice, it was observed that the enzyme column was very stable. Such results are in contrast to what has bee observed for naringinase fron A. niger. Therefore, it is quite possible that the sugars in the fruit juice which play a role as competitive or non-competitive inhibitors on naringinase may account for the stability of the enzyme column during successive debittering of grapefruits juice.