Use of Response Surface Methodology to Predict Optimal Conditions of Kluyveromyces lactis Permeabilization by a Physical Method

J. Teles de Faria, M. Lopes Moraes, A. Del Borghi, A. Converti, F. M. Lopes Passos, L. A. Minim, A. P. de F. C. Vanzela and F. Coelho Sampaio

Abstract
Kluyveromyces lactis is an important commercial source of β-galactosidase, an enzyme of major concern for dairy industry. Among the methods for β-galactosidase recovery, cell permeabilization is the best alternative, but it is influenced by a number of operating conditions that need to be optimized. Aim of this study was to determine the best experimental conditions for yeast cells permeabilization by physical disruption with glass beads. Influence of glass beads and dry biomass amounts and process time was investigated varying these independent variables according to a central composite rotatable experimental design. A third order polynomial equation was fitted to the experimental data of permeabilized cells β-galactosidase activity, and the Response Surface Methodology employed for optimization. Optimum permeabilization conditions (0.90 g glass beads, 2.00 g dry biomass and 8.0 min of treatment) ensured a maximum β-galactosidase activity (6,434 mmol L–1 oNP min–1 g–1) in reasonable agreement with the yield reproduced under the same conditions (5,585.40 mmol L–1 oNP min–1 g–1).

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Keywords
cheese whey, Kluyveromyces lactis, yeast, glass beads, β-galactosidase