SUMMARY
Production and partial characterization of b -galactosidase from Kluyveromyces lactis grown in deproteinized whey
The purpose of this work was to optimize the b -galactosidase production by Kluyveromyces lactis, applying the Surface Response Methodology (SRM) and using deproteinized whey as fermentation medium. An Orthogonal Central Compound Design (OCCD) was used without repetition, with four factors: temperature, pH, agitation speed and fermentation time. Then, enzyme activity (U/ml) as response variable was used. Thirty trials in twenty-five treatments, with six repetitions at the central point, were carried out, in a New Brunswick Bioflo 2000 fermentor with a volume of 2 liters. The deproteinized whey obtained by thermocoagulation was chemically analyzed . The results were: moisture 93,83%, total solids 6,17%, protein 0,44%, lactose 4,85%, acidity 0,43% and pH 4,58. The best conditions in the enzyme production were : temperature 30,3 °C, pH 4,68, agitation speed 191 r.p.m. and fermentation time 18,5 h. with an enzyme production of 8,3 U/ml. The degree of purification obtained was 7,4 times and the yield was 50,8% . The purified enzyme had an optimum temperature of 60 °C and a pH of 6,2. This work shows that the yeast Kluyveromyces lactis grown in deproteinized whey is able to produce the enzyme b -galactosidase and SRM can be used in the fermentology processes, specifically in determining the best suitable operation conditions.

Keys word: Whey, b -galactosidase, Kluyveromyces lactis, surface response methodology.



Recibido: 11/06/2002
Aceptado: 30/04/2003

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