Enzymatic generation of lactulose in sweet and acid whey: Optimization of feed composition and structural elucidation of 1-lactulose

摘要

Prebiotics are rising in interest in commercial scale productions due to increasing health awareness of consumers. Under bio-economic aspects, sweet and acid whey provide a suitable feed medium for the enzymatic generation of prebiotic lactulose. Since whey has a broad variation in composition, the influence of the feed composition on the concentration of generated lactulose was investigated. The influence of lactose and fructose concentration as well as enzymatic activity of two commercially available beta-galactosidases were investigated. The results were evaluated via response surface analysis with a quadratic model containing pairwise interaction terms. The optimal feed composition yielding a theoretical maximal amount of lactulose was determined as 1.28 or 0.74 mol/kg fructose and 0.17 or 0.19 mol/kg lactose with an enzymatic activity of 2.0 or 2.8 mu kat/kg for acid (pH 4.4) or sweet (pH 6.6) whey. Furthermore, the major reaction product was isolated and subsequently, the structural identity was elucidated and verified via extensive NMR analysis.