Characterization of aqueous two-phase systems based on polydisperse phase forming polymers: Enzymatic hydrolysis of starch in a PEG-starch aqueous two-phase system

A new method for determination of the binodial of an aqueous two-phase system, using spectrophotometric measurements of the turbidity, is described in this article. The method is especially designed to characterize phase systems composed of polydisperse phase components. It gives information about the area representing the transition from homogeneous solution to a two-phase system. The two-phase systems studied were first a conventional Dextran T40-polyethylene glycol 20M (PEG 20M) system, then a less-well-defined phase system based on PEG 20M and partially hydrolyzed starch. The PEG 20M-starch system could be changed with respect to the volume ratio between the phases with time using hydrolytic enzymes, and the possibility of using the glucose released from the starch polymer is pointed out. Then the system is transformed to an extractive biconversion where the bottom phase polymer also served as the substrate.