Synthesis of Galactooligosaccharides in Milk and Whey: A Review

Abstract

Galactooligosaccharides (GOS) are synthesized by the enzyme β-galactosidase during the hydrolysis of lactose. In this so-called transgalactosylation reaction the galactosyl moiety is transferred to another sugar molecule instead of water resulting in oligosaccharides of different chain lengths and glycosidic linkages. Because their structures are similar to oligosaccharides present in human breast milk, they act as prebiotics, which has been shown for infants and adults to be alike. While so far most of the research to maximize GOS yield has been carried out using buffered lactose solution as a starting material, more and more work is now conducted with dairy by-products such as whey and whey permeate, or even milk, for direct GOS synthesis in order to develop new GOS-enriched dairy products. This review aims to summarize the results obtained with various dairy liquids, and it rates their suitabilities to act as raw material for GOS production. Most of the studies using whey or milk have been carried out with enzymes from Aspergillus oryzae, Kluyveromyces lactis, Bacillus circulans, Streptococcus thermophilus, and several Lactobacillus species. As the initial lactose concentration (ILC) is known to be a crucial factor for high GOS yield, most of the research has been done with concentrated or supplemented milk and whey. However, a clear dependency on ILC could only be observed for the A. oryzae lactase, indicating a strong influence of milk components like minerals and proteins on the transfer activities of most enzymes.

Bioconversion of Milk Permeate with Selected Lactic Acid Bacteria Strains and Apple By-Products into Beverages with Antimicrobial Properties and Enriched with Galactooligosaccharides

“…This is likely to be the reason to not having been found a high positive correlation between GOS and TTA, LAB and the initial lactose content, and a high negative correlation between GOS and pH. The ability of Lactobacillus spp., P. pentosaceus and P. acidilactici to synthesized GOS in fermented dairy media was reported by other authors [40][41][42][43]. However, observed differences between results in these studies are highly influenced by the type of microorganisms used and the initial substrate composition.…”

Whey valorization using transgalactosylation activity of immobilized β‐galactosidase

“…Namely, the obtained maximum GOS concentration in case of the immobilized preparation was achieved for 4 h, while the same GOS concentration with the soluble enzyme was achieved in 10 h. Therefore, it can be concluded that enzyme specificity shifted towards the reaction of transgalactosylation, bearing in mind that same hydrolytic activities of both preparations were employed in the reaction, and that 2.5‐fold enhancement of reaction productivity was achieved. Results of this study are important since there are a few examples of applied immobilized preparations for concentrated whey transformation (Jovanovic‐Malinovska et al ., ), although this reaction is already well established, as it can be seen in several review papers (Nath et al ., ; Fischer & Kleinschmidt, ).…”

“…In the preliminary stage of research, the reasoning of whey usage for GOS synthesis was tested under previously defined optimum conditions for the relevant enzyme (50 °C and pH 4.5). Since it is scientifically confirmed that higher lactose concentrations positively influence the GOS synthesis process (Gosling et al ., ; Vera et al ., ), and that the most successful studies considered using either concentrated or lactose supplemented whey and whey permeates (Fischer & Kleinschmidt, ), several initial whey concentrations (10–40% w/w) were examined (Fig. ).…”

“…Moreover, GOS are distinguished by high thermal and acid stability, excellent taste quality, low sweetness and caloric value that secure its wide application in the food industry (Van Leusen et al, 2014;Singla & Chakkaravarthi, 2017). Therefore, transgalactosylation can tune whey into value-added product (Nath et al, 2016;Fischer & Kleinschmidt, 2018) that can be further on utilized as food and feed functional ingredient (Fonseca et al, 2017).…”

Phenotypic and genetic characterization of differential galacto-oligosaccharide utilization in Lactobacillus plantarum

“…In situations where breastfeeding is not feasible, infant formula provides an alternative to mimic the nutritional composition of breastmilk 3 . Although bovine milk is mostly devoid of oligosaccharides, lactose based oligosaccharides can be produced in large quantities by incubation of various microbial β-galactosidases with high concentrations of lactose to catalyze transglycosylation reactions to produce galacto-oligosaccharides (GOS) 4 . The chemical composition of GOS components (i.e., linkage type, and degree of branching and degree of polymerization) is highly dependent of the reaction conditions, as well as the specific β-galactosidase enzyme used during production, which results in GOS preparations that are commonly a composite of multiple different oligosaccharides 5 .…”