Application of response surface methodology in the permeabilization of yeast cells for lactose hydrolysis

Enzymatic hydrolysis of lactose is one of the most promising biotechnological applications in the food industry, which can be used to solve the problems of lactose intolerant individuals. However, the industrial applications of enzymatic hydrolysis processes are being hampered, due to intracellular location of the yeast enzyme, which makes its extraction difficult and expensive However, the problem of enzyme extraction and poor permeability of cell membrane to lactose can be overcome using permeabilization technique. Response surface methodology was used to investigate the effect of different parameters (concentration, temperature and treatment time) on the permeabilization of Kluyveromyces marxianus cells. The experimentation was aimed to find the values of process variables to achieve maximal β-galactosidase activity by numerical optimization technique. The optimum operating conditions for permeabilization process were 49.6% (v/v) ethanol concentration, 23 °C temperature and process duration of 18 min. At these conditions of process variables, the predicted value of enzyme activity was found to be 1573 IU/g. These permeabilized yeast cells displayed 89.7% lactose hydrolysis in skim milk after 150 min of incubation time.