High fructose syrup production from whey lactose using microbial beta-galactosidase and glucose isomerase

A powdered crude whey lactose preparation with 97.0% lactose content was used for hydrolysis in various aqueous two-phase systems (ATPSs) by β-galactosidase of Aspergillus oryzae. Different ATPSs were formed by using two polymers (PEG, dextran T500) and one polymer and a salt (PEG 20000, sodium citrate). The PEGs with 3 different molecular weights were tested at 3 different concentrations in the PEG/Dextran T500 and 3 different concentrations of sodium citrate in the PEG 20000/sodium citrate systems. These systems were shaken at 25 °C for 60 min, and immediately centrifuged for phase separation. The top phase of PEG 20000/Dextran T500 (5:5, w/w) had the highest glucose content. In the study it was used as glucose syrup to produce high fructose syrup in a glass column system with glucose isomerase of Streptomyces rubiginosus loaded to the top of the column. The product was collected in a flask placed underneath the column and recirculated at 56°C for 1 h to produce fructose syrup containing 62.28% fructose and 42.20% glucose.