Sunday, August 12, 2012
Columbia Hall, Terrace Level (Washington Hilton)
Invertase (B-D-fructofuranosidase EC 3.2.1.26) hydrolyzes sucrose into an equimolar mixture of glucose and fructose, known as invert sugar. Invert sugar is widely use in food and brewing industries because minimize the chrystallization and avoid the solubilization process of solid sugar. Most of industrial invertases displayed substrate inhibition at low sucrose concentration (10%). In order to overcome this problem, the osmotolerant yeast Candida lactis-condensi MpIIIa, able to grown at high concentrations of sucrose (60%), was used as a source of invertase. Economic production of invert sugar could be carried out by immobilized invertase. In this work, the invertase from Candida lactis-condensi MpIIIa was covalently immobilized on nylon-6 with an immobilization efficiency of 89% and invertase activity of 5299 U/g of nylon-6, one of the highest activities reported so far. The nylon-6 immobilized invertase showed optimal activity at pH 5.5 and 60oC in 50 mM acetate buffer. The km and Vmax were measurement as 67.15 mM of sucrose and 9550 umol/min/g of nylon-6, respectively. The enzyme activity on nylon-6 immobilized invertase was stimuled by Mn 2+ (84%) but completely inhibited by Hg 2+. Immobilized enzyme retained 50% of initial activity after 550 reuses at 25oC in 10% sucrose. The immobilized invertase showed great storage stability retaining 75% of its original activity after 10 months a 4oC.