Comparison of PEG/fractionated dextran and PEG/industrial grade dextran aqueous two-phase systems for the enzymic hydrolysis of starch

The aqueous two phase systems of polyethylene glycol (PEG)/fractionated dextran (DEX500) and PEG/industrial grade dextran (DEXI) were examined for the semi-continuous hydrolysis of starch. DEXI coagulates immediately as agitation stops and forms a biphasic system promptly whereas DEX500 forms clearer phases at a slower rate though. The partitioning of DEXI in the PEG phase is considerably lower compared to that for DEX500. Addition of starch in the biphasic systems was found to increase phase separation rate and dextran partition to dextran phase. Viscosities of the DEXI systems were only 10% higher than those of DEX500. Semi-continuous hydrolysis in the two phase systems exhibit steady performance for five cycles with 123.5% and 100.2% conversion of the initial starch load, for DEX500 and DEXI, respectively. The PEG/DEXI system presents almost equivalent performance to PEG/DEX500 system and has considerable lower cost than the latter. (c) 2006 Elsevier Ltd. All rights reserved.