Effi cient Degumming of Rice Bran Oil by Immobilized PLA1 from Thermomyces lanuginosus

Abstract

Phospholipase A 1 (PLA 1 ) immobilized in calcium alginate can eff ectively 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 PLA 1 hydrolase from Thermomyces lanuginosus was comparatively faster than of its free form. The rate of phospholipid hydrolysis by PLA 1 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 fa y 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 PLA 1 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 PLA 1 removed phosphorus from oil by 94.12 % under the same experimental conditions (pH=6, 60 C, 1-hour incubation). Both the free PLA 1 and its immobilized form had shown extended rates of hydrolysis in a calcium-rich environment. The mass fractions of free fa y 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 signifi cant reduction in colour and restoration of iodine value to the desired level.