Synthesis and purification of galacto-oligosaccharides: state of the art

Abstract

Lactose-derived non-digestible oligosaccharides are prominent components of functional foods. Among them, galacto-oligosaccharides (GOS) outstand for being prebiotics whose health-promoting effects are supported on strong scientific evidences, having unique properties as substitutes of human milk oligosaccharides in formulas for newborns and infants. GOS are currently produced enzymatically in a kinetically-controlled reaction of lactose transgalactosylation catalyzed by β-galactosidases from different microbial strains. The enzymatic synthesis of GOS, although being an established technology, still offers many technological challenges and opportunities for further development that has to be considered within the framework of functional foods which is the most rapidly expanding market within the food sector. This paper presents the current technological status of GOS production, its main achievements and challenges. Most of the problems yet to be solved refer to the rather low GOS yields attainable that rarely exceed 40 %, corresponding to lactose conversions around 60 %. This means that the product or reaction (raw GOS) contains significant amounts of residual lactose and monosaccharides (glucose and galactose). Efforts to increase such yields have been for the most part unsuccessful, even though improvements by genetic and protein engineering strategies are to be expected in the near future. Low yields impose a burden on downstream processing to obtain a GOS product of the required purity. Different strategies for raw GOS purification are reviewed and their technological significance is appraised.

Capillary electrophoresis with stationary nanogel zones of galactosidase and Erythrina cristagalli lectin for the determination of β(1–3)-linked galactose in glycans

“…In addition, some galactosidases also function as a transgalactosidase enzyme, conjugating the liberated galactose residues back to a glycan or oligosaccharide terminus. [26] Lectins avoid confounding results that may be obtained using enzymes with different properties and from different sources.…”

“…The potential of some galactosidase enzymes to simultaneously function as a transgalactosidase as well as an exoglycosidase must also be considered. [26] Additionally, the specificity, catalytic rate, and conditions required for the enzyme reaction must be defined. [27] To expand research in glycan characterization, analytical technologies are required that are inexpensive, simple to implement and have potential for automated analysis.…”

Whey valorization using transgalactosylation activity of immobilized β‐galactosidase

“…Thus, with the genuine progress of biotechnology whey is becoming a substrate of choice for diverse food and pharmaceutical industries (Kareb & A€ ıder, 2018;Lata et al, 2018). With the increased interest in functional foods and prebiotics, one of the promising approaches for whey valorization through conversion of present lactose by virtue of transgalactosylation activity of b-galactosidase (Torres et al, 2010;Vera et al, 2016;Panesar et al, 2018). Namely, wide range of physiologically active compounds collectively named galacto-oligosaccharides (GOS) could be produced by b-galactosidase mediated transfer of galactosyl moiety onto other saccharide molecules, resulting in the formation of a complex mixture of carbohydrates notably varying in polymerization degree, type of linkages, and their properties (Gosling et al, 2010;Carevi c et al, 2016a;Chen & G€ anzle, 2017).…”

Biocatalysis in the winemaking industry: Challenges and opportunities for immobilized enzymes

“…After more than four decades of development, enzyme immobilization is still facing many challenges with ample room for future opportunities in different fields of applications. Some industrial examples of the use of immobilized enzymes are found in the fields of sweeteners (DiCosimo, McAuliffe, Poulose, & Bohlmann, 2013), interesterification of edible oils and fats (Macrae & Hammond, 1985;Samoylova, Sorokina, & Parmon, 2016), prebiotics (Vera et al, 2016), and antibiotics (Illanes & Valencia, 2017). From all the advantages associated to immobilized enzymes as process catalysts, two are particularly relevant to their application in winemaking, namely, the production of a catalyst-free product and the development of a continuous process (Bolivar, Eisl, & Nidetzky, 2016;Poppe, Fernandez-Lafuente, Rodrigues, & Ayub, 2015).…”