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

Abstract

This 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 applications The 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.

Continuous Production of Galacto-Oligosaccharides by an Enzyme Membrane Reactor Utilizing Free Enzymes

“…Carbohydrate composition (glucose, galactose, and DP2-6 fractions) of samples was determined by the HPLC method, as previously described in [32]. In brief, a Thermo Separations HPLC system equipped with a Shodex R-101 refractive index detector (Showa Denko Europe GmbH, Munich, Germany) and a N2000 Chromatography Data System from Science Technology (Hangzhou) Inc. (Hangzhou, China) was used, employing an RNM carbohydrate 8% Na + 300 × 7.8 (Phenomenex, Torrance, CA, USA) analytical column at 50 • C at 0.2 mL•min −1 with a prefiltered (2 µm) DI water as mobile phase.…”

“…In brief, a Thermo Separations HPLC system equipped with a Shodex R-101 refractive index detector (Showa Denko Europe GmbH, Munich, Germany) and a N2000 Chromatography Data System from Science Technology (Hangzhou) Inc. (Hangzhou, China) was used, employing an RNM carbohydrate 8% Na + 300 × 7.8 (Phenomenex, Torrance, CA, USA) analytical column at 50 • C at 0.2 mL•min −1 with a prefiltered (2 µm) DI water as mobile phase. Specification of standards used for peak identification can be found in [32]. Samples taken from the product (= permeate) stream of the EMR were not subject to heat deactivation prior to HPLC analysis unless otherwise stated.…”

“…Previous studies have also shown that a further increase in initial lactose concentration (above ca. 30 w/w%) does not lead to an increased yield [32,37]. The space-time yield, which is the amount of product (DP3-6) obtained per hour for one kg of reactor content, was calculated as 18.8 g•kg −1 •h −1 (based on 6 h processing time and normalized to 1 kg reactor content).…”

Production of high‐purity galacto‐oligosaccharides by depleting glucose and lactose from galacto‐oligosaccharide syrup with yeasts

“…Data collection and peak integration was performed with N2000 Chromatography Data System and N2000 Photographic Data Workstation software package (Science Technology Inc., Hangzhou, China). Peak identification and determination of the concentration of individual carbohydrate fractions was performed as described earlier in (Pázmándi, Maráz, Ladányi, & Kovács, 2018). Analytic grade ethanol was used as a standard to detect and quantify ethanol production.…”

“…A 20-or 100-ml GOS fermentation media in 100-or 500-ml Erlenmeyer flasks, respectively, were inoculated with 5 × 10 6 cells per ml and incubated by shaking with 220 rpm at 30 C. (Pázmándi, Maráz, Ladányi, & Kovács, 2018). Analytic grade ethanol was used as a standard to detect and quantify ethanol production.…”