Application of response surface methodology for maximal lactose hydrolysis in whole milk using permeabilised yeast cells

Panesar, P. (2008) Application of response surface methodology for maximal lactose hydrolysis in whole milk using permeabilised yeast cells. Acta Alimentaria, 37 (2). pp. 191-203. ISSN 0139-3006

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Abstract

Kluyveromyces marxianus cells as a source of β-D-galactosidase were employed for the production of lactose hydrolysed whole milk. The yeast cells were permeabilised to overcome the problem of enzyme extraction and poor permeability of cell membrane to lactose. To analyse and optimise the process variables for lactose hydrolysis, the experiments were conducted according to the Central Composite Rotatable Design (CCRD) using response surface methodology. The independent process variables for lactose hydrolysis were biomass concentration, temperature, agitation and incubation time. Statistical analysis of the results showed that, in the range studied, linear terms of biomass concentration, incubation time and process temperature had a significant effect (P<0.01) on lactose hydrolysis, however, the effect of agitation on lactose hydrolysis was significant when compared with stationery conditions. Numerical optimisation technique was applied to achieve the maximum possible lactose hydrolysis value. The optimum process conditions for lactose hydrolysis were 120 mg biomass (dry wt), 33.6 °C temperature, 105 r.p.m. agitation and 147 min of incubation time. Corresponding to these optimum conditions, the predicted value of lactose hydrolysis was found to be 88.6%, which was experimentally verified.

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