**3.2 Microbial bioprocesses**

*Lactose and Lactose Derivatives*

tional ingredient [16, 40].

**3.1 Biocatalytic processes**

*3.1.1 Galacto-oligosaccharides*

cream and bakery products [45].

type laboratory scale membrane filtration system [39]. Even though this still an expensive procedure to extract sialyllactose, some infant formulae use it as func-

**3. Functional compounds bio-produced using lactose as substrate**

Galacto-oligosaccharides [Gal-(Gal)n-Glu] are lactose-derived non-digestable oligosaccharides (GOS) recognized as relevant functional compounds. Industrially, GOS are produced using CW lactose as substrate through biocatalytic reaction. Lactose is transgalactosylated by ß-galactosidases enzymes (E.C. 3.2.1.23) from several microbial strains [44]. GOS are the best substitute for human oligosaccharides, have a sweet taste, low energy value (2 kcal/g), as well as tolerate high temperatures and low pHs. So, they are widely used in the food industry as functional ingredient in the manufacturing of infant formula, confectionary, chewing gum, yogurt, ice

Previous studies have demonstrated the impact of GOS promoting gut health and well-being. These lactose-derived prebiotics serve as substrates for the microbiota, improve saccharolytic metabolic activities and stimulate the growth of indigenous bifidobacteria and lactobacilli. In consequence, the formation of volatile fatty acids, lowering of the luminal pH and decreased formation of toxic secondary bile acids are microbial metabolic associated effects. Also, they inhibit the formation of toxic bacterial metabolites, such as ammonia, hydrogen disulphide, phenolic compounds and biogenic amines [44]. Moreover, GOS have a bifidus factor similar to the effect of human milk oligosaccharides stimulating the growth of specific intestinal microbiota, improving the intestinal motility, enhancing immunity, promoting the synthesis of vitamins, reducing the high levels of cholesterol and triglycerides and decreasing the risk of colon cancer development [45, 46].

Lactosucrose is an oligosaccharide comprising Gal, Fru and Glu. This carbohydrate molecule (C18H38O16; MW, 510.4 g/mol) is a ß-D-fructofuranosyl-4-O- ß-Dgalactopyranosyl-α-D-glucopyranoside [16]. Lactosucrose can be regarded as a condensate of sucrose and galactose molecules or lactose and fructose molecules. Production protocols include transferring the ß -galactosyl group produced by the decomposition of lactose to the C4 hydroxyl group of glucosyl in sucrose by the

*In vivo* studies have demonstrated the ability of sialyllactose to improve positively in health. Pathogenic microorganisms have been effectively inhibited using it [16, 40]. It was reported that the consumption of dietary sialyllactose modified the colonic microbiota, e.g. Bacteroidetes were significantly increased, meanwhile Firmicutes and Cyanobacteria were significantly decreased. Moreover, this lactosederived prebiotic was able to diminish stressor-induced alterations in colonic mucosa and anxiety-like behavior [41]. One of the major causes of morbidity and mortality in premature infants is necrotizing enterocolitis (NEC). Recently, it was found that human milk oligosaccharides 2′-fucosyllactose and 6′-sialyllactose can reduce NEC and attenuate NEC inflammation [42]. In addition, intact sialylated oligosaccharides can be absorbed in concentrations high enough to modulate the immunological system and facilitate proper brain development during infancy [43].

**80**

*3.1.2 Lactosucrose*
