Study of PEG-substrate biphasic systems for the enzymic hydrolysis of gelatinised crude corn starch

Enzymic hydrolysis of gelatinised crude corn starch in a semi-continuous pr ocess was studied in aqueous biphasic systems, where starch served both as substrate and phase forming polymer in combination with polyethylene glycol (PEG). Starch concentration as well as PEG concentration and molecular wei ght affect both phase ratio and separation time. Pre-treatment of starch wi th amylolytic enzymes also affects the characteristics of the biphasic syst em to an extent, which depends on the type of enzyme used. A two-phase syst em, comprising 7.5% PEG and 5% starch, was used for the semi-continuous hyd rolysis of corn starch by glucoamylase. The system performed steadily for f ive reaction cycles, exhibiting up to 20% glucose uptake per reaction cycle . (C) 2000 Elsevier Science Ltd. All rights reserved.