Optimization of the Phase System Composition of Aqueous Two-Phase System for Extraction of 2,3-Butanediol by Theoretical Formulation and Using Response Surface Methodology

S. G. and T. Swaminathan

Abstract
In recent days the aqueous two-phase extraction is attracting lot of attention in biotechnology. In this study theoretical exercise was taken leading to the development of biondal and tie-line equation, which eventually helped in calculation of total, top and bottom phase compositions theoretically for given pair of volume ratio and tie-line length and vice-versa. Experiments were done using response surface methodology to find the effects of volume ratio and tie-line lengths and, thereby, the phase composition of an aqueous two-phase system and their mutual interactions on (equilibrium) distribution coefficient of 2,3-butanediol and settling time, separately. A 22 full-factorial central composite experimental design was adopted and the data were analysed by statistical techniques. The optimum volume ratio and tie-line length were found to be 1.61 and w = 22.84 %, respectively, in the case when distribution coefficient was the response quantity and w = 1.89 and 22.22 %, respectively, when settling time was the response quantity. The final optimized phase compositions were found to be w = 8.7% dextran 40000 and w = 9.0 % polyethylene glycol 6000 in the case, where partition coefficient was the response parameter and the corresponding values were w = 8.0% and 9.2%, respectively, when settling time was the response quantity. The maximum distribution coefficient of 2,3-butanediol and the minimum settling time in the corresponding optimized phase composition were calculated to be 1.114 and 8.5 min from the respective equations.

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Keywords
Aqueous two-phase, binodal curve, statistical optimization techniques, separation, 2,3-butanediol