Efficient Degumming of Rice Bran Oil by Immobilized PLA₁ from Thermomyces lanuginosus

Phospholipase A₁ (PLA₁) immobilized in calcium alginate can effectively overcome the mass transfer resistance at the lipid-water interface making more room for the enzyme to separate itself from the products of reaction and to bind with the next available molecule at the interface. The reaction of an immobilized PLA₁ hydrolase from Thermomyces lanuginosus was comparatively faster than of its free form. The rate of phospholipid hydrolysis by PLA₁ was studied in calcium-rich and calcium-depleted environments; and the extent of phosphorus removed from the crude rice bran oil as well as the amount of free fatty acids produced during the reaction were used as indices for analysing the rate of enzymatic hydrolysis under standard conditions of pH, temperature, time of incubation and agitation. The immobilized PLA₁ was found to be superior in removing phosphorus in the presence of 10 mM bivalent calcium ions in a solution. As compared to a maximum of 72.52% phosphorus removed by 0.01 kg of free enzyme per kg of oil, the same amount of immobilized PLA₁ removed phosphorus from oil by 94.12% under the same experimental conditions (pH=6, 60 °C, 1-hour incubation). Both the free PLA₁ and its immobilized form had shown extended rates of hydrolysis in a calcium-rich environment. The mass fractions of free fatty acids produced by the free enzyme and by its immobilized form were 14.9 and 14.16%, respectively, under the above experimental conditions. The removal of phosphorus from oil was accompanied by a significant reduction in colour and restoration of iodine value to the desired level.