Contribuição ao estudo da produção de β- galactosidase por fermentação de soro de queijo com Kluyveromyces marxianus

Abstract

The enzymatic hydrolysis of lactose for P-galactosidase plays a important hole in the Processing of miiky products as the production of lactose-hydrolyzed milk for consumption for intolerant persons to lactose and the prevention of the crystallization in dairy products. In this work was studied the influences of nutrient concentrations in the culture médium based on cheese whey with the objective of producing P-galactosidase from Kluyveromyces marxianus. The fermentations were carried out in a shaker by 12 hours at 30°C, initial pH 5,5 under agitation of 150 rpm starting with a initial cellular concentration of lx 107 cells/mL, varying the initial concentrations of lactose, yeast extract and salts. During the fermentative process the analyzed parameters were: lactose consumption, cellular concentration and the enzymatic activity. For extraction of the enzyme, the cells obtained in the end of each fermentation were separate for centrifogation, suspended in 10 mL of phosphate pH 6,5 buffer and distributed in erlenmeyers, to the which it was added 2% (v/v) of chloroform. For enzymatic activity determination was used the initial rates method for the reaction of lactose hydrolysis. An enzymatic activity of 28,0 UGl/mL was obtained, using as culture médium cheese whey, in a concentration of lactose of 50 g/L, supplemented with the salts K2HPO4, (NH4)2SO4 and MgSO4, in the concentrations of 5,0; 6,0 and 0,6 g/L, respectively and yeast extract of 12 g/L. In these conditions the cellular concentration reached 4,8 g/L of dry mass. The cheese whey supplemented with salts and yeast extract was an appropriate médium for cellular growth and enzyme synthesis.