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

• Published in: Food chemistry Vol. 305; p. 125481
• Main Authors: Schmidt, Christian M., Balinger, Franziska, Conrad, Jürgen, Günther, Johannes, Beifuss, Uwe, Hinrichs, Jörg
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2020
• Subjects: beta-Galactosidase - metabolism; Fructose - metabolism; Hydrogen-Ion Concentration; Isomerism; Lactose - metabolism; Lactulose - isolation & purification; Lactulose - metabolism; Magnetic Resonance Spectroscopy; Nuclear magnetic resonance; Prebiotic; Response surface analysis; Transgalactosylation; Valorization; Whey - chemistry; Whey - metabolism; β-Galactosidase; Response surface analysis; Nuclear magnetic resonance; Transgalactosylation; Prebiotic; Valorization; β-Galactosidase
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2019.125481

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 β-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 μkat/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. •Valorization of sweet and acid whey by generation of prebiotic lactulose•Optimization of feed composition using central composite design.•No interaction between saccharide concentration and enzymatic activity was found.•The major reaction product was verified as 1-lactulose via NMR.