The impact of membrane pretreatment on the enzymatic production of whey‐derived galacto‐oligosaccharides

Abstract

AbstractThis study presents a multistep process for the valorization of whey that involves membrane filtration techniques to fractionate whey compounds and the subsequent enzymatic conversion of lactose into galacto‐oligosaccharides with a degree of polymerization (DP) of 3–5. Partially demineralized whey was first concentrated and diafiltered by ultrafiltration (UF) to obtain whey protein isolates. Over 97% of the initial amount of lactose was recovered into the permeate which was then concentrated by nanofiltration (NF) up to 330 g L−1. Finally, a systematic study was performed to investigate the hydrolytic and transgalactosylation activity of Biolacta N5, a Bacillus circulans‐derived β‐galactosidase, on whey‐derived substrates consisting of lactose in various concentrations. Hydrolysis was especially pronounced for UF permeates with low lactose concentrations (< 50 g L−1), whereas transgalactosylation was dominant for streams concentrated by NF, obtaining comparable yields of the DP3‐5 fractions (∼ 35%) for moderate and high NF concentration factors.Practical applicationsThe market for functional foods and dairy‐based functional beverages represents a growing segment of the global food industry. This article describes a technique for the valorization of whey that is based on the fractionation of whey constituents and the subsequent bioconversion of lactose into GOS. GOS are prebiotic substances with favorable technological properties such as low viscosity and good pH and temperature stability. These low‐calorie sweeteners can be added to a wide range of foods to increase product functionality. The here proposed multiproduct process has potential applications in whey management practice. The reported experimental data on the performance of the processing steps and the proposed approaches to the synchronization of the individual operations is useful for the design of whey valorization processes with reduced waste and energy consumption.