Purification and characterization of an invertase and a transfructosylase from Aspergillus terreus

Two intracellular invertases from Aspergillus terreus were purified and characterized. Invertase 1 has been shown maximal activity at pH 3.0 and optimum temperature at 60°C, while invertase 2 presented maximal activity at pH 4.6 and optimum temperature at 55°C. Km of invertase 1 and 2 for sucrose were 9.8 and 6.2 mM, respectively. Invertase 2 showed high thermostability presenting half‐life of 44, 14.9, and 2 hr at 40, 55, and 60°C, respectively. Gel filtration and SDS‐PAGE analysis revealed that invertase 2 has a dimeric structure composed by two monomers of 32 kDa. Fructose was a competitive inhibitor for invertase 2 presenting Ki of 61.5 mM. Besides hydrolytic activity, invertase 2 also showed transfructosylating activity producing fructooligosaccharides. The enzymes have potential to be applied in food industry since its product, inverted sugar, is used in candies and syrup production, while fructooligosacharides are prebiotics, low calorie and noncariogenic sweeteners. Practical applications Enzymes invertases hydrolyze sucrose in glucose and fructose producing inverted sugar. This product is widely used in food industry to produce jams, syrups, and fondant fillings for chocolates. Besides hydrolysis activity, some invertases can also present transfructosylating activity producing fructooligosaccharides. These oligosaccharides can act as prebiotic, providing beneficial health effects and can be used as low calorie and noncariogenic sweeteners. Aspergillus terreus produced two intracellular enzymes, one exclusively invertase, and the other, invertase and transfructosylase. The enzymes were purified and characterized in this study. This is an important step on screening new enzymes able to produce inverted sugar and fructooligosaccharides from sucrose.