Lactose and lactose-derived oligosaccharides: More than prebiotics?

In vitro and in vivo digestibility of prebiotic galactooligosacharides synthesized by β-galactosidase from Lactobacillus delbruecki subsp. bulgaricus CRL450

BACKGROUND

The general assumption that prebiotics reach the colon without any alterations has been challenged. Some in vitro and in vivo studies have demonstrated that 'non-digestible' oligosaccharides are digested to different degrees depending on their structural composition. In the present study, we compared different methods aiming to assess the digestibility of oligosaccharides synthesized by β-galactosidase (β-gal) of Lactobacillus delbruecki subsp. bulgaricus CRL450 (CRL450-β-gal) from lactose, lactulose and lactitol.

RESULTS

In the simulated gastrointestinal fluid method, no changes were observed. However, the oligosaccharides synthesized by CRL450-β-gal were partially hydrolyzed in vitro, depending on their structure and composition, with rat small intestinal extract (RSIE) and small intestinal brush-border membrane vesicles (BBMV) from pig. Digestion of some oligosaccharides increased when mixtures were fed to C57BL/6 mice used as in vivo model; however, lactulose-oligosaccharides were the most resistant to the physiological conditions of mice. In general β (1→6) linked products showed higher resistance compared to β (1→3) oligosaccharides.

CONCLUSION

In vitro digestion methods, without disaccharidases, may underestimate the importance of carbohydrates hydrolysis in the small intestine. Although BVMM and RSIE digestion assays are appropriate in vitro methods for these studies, in vivo studies remain the most reliable for understanding what actually happens in the digestion of oligosaccharides. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Distinguishing α/β-linkages and linkage positions of disaccharides in galactooligosaccharides through mass fragmentation and liquid retention behaviour

Galactooligosaccharides (GOS) are important prebiotics with function closely related to their structure. However, a comprehensive overview of the structure-function relationship is still limited due to the challenge in characterizing multiple isomers in GOS. This study presents a strategy of combining both hydrophilic interaction liquid chromatography (HILIC) retention time and tandem mass spectrometry (MS/MS) fragmentation pattern to distinguish α/β-linkages and linkage positions of disaccharide isomers in GOS through HILIC-MS/MS analysis. The results indicated that the ratio of m/z 203.0524 to m/z 365.1054 could distinguish α/β-linkages, while the ratios of m/z 347.0947 to m/z 365.1054, m/z 245.0642 to m/z 365.1054 and HILIC retention time could distinguish (1 → 2), (1 → 3), (1 → 4) and (1 → 6) linkages. The above rules enabled effective characterization of disaccharides in GOS-containing food samples, including milk powder, rice flour, drink, yogurt. This method can be used in the quality control of GOS and future research on the structure-specific health effects of GOS.

Invited review: Properties of β-galactosidases derived from Lactobacillaceae species and their capacity for galacto-oligosaccharide production

β-galactosidase (enzymatic class 3.2.1.23) is one of the dairy industry's most important and widely used enzymes. The enzyme is part of a large family known to catalyze hydrolysis and transglycosylation reactions. Its hydrolytic activity is commonly used to decrease lactose content in dairy products, while its transglycosylase activity has recently been used to synthesize galacto-oligosaccharides (GOS). During the past couple of years, researchers have focused on studying β-galactosidase isolated and purified from lactic acid bacteria. This review will focus on β-galactosidase purified and characterized from what used to be the Lactobacillus genera. Furthermore, particular emphasis is given to its kinetics, biochemical characteristics, GOS production, market, and utilization by Lactobacilllaceae species.

Associations among Milk Microbiota, Milk Fatty Acids, Milk Glycans, and Inflammation from Lactating Holstein Cows

Milk oligosaccharides (MOs) can be prebiotic and antiadhesive, while fatty acids (MFAs) can be antimicrobial. Both have been associated with milk microbes or mammary gland inflammation in humans. Relationships between these milk components and milk microbes or inflammation have not been determined for cows and could help elucidate a novel approach for the dairy industry to promote desired milk microbial composition for improvement of milk quality and reduction of milk waste. We aimed to determine relationships among milk microbiota, MFAs, MOs, lactose, and somatic cell counts (SCC) from Holstein cows, using our previously published data. Raw milk samples were collected at three time points, ranging from early to late lactation. Data were analyzed using linear mixed-effects modeling and repeated-measures correlation. Unsaturated MFA and short-chain MFA had mostly negative relationships with potentially pathogenic genera, including Corynebacterium, Pseudomonas, and an unknown Enterobacteriaceae genus but numerous positive relationships with symbionts Bifidobacterium and Bacteroides. Conversely, many MOs were positively correlated with potentially pathogenic genera (e.g., Corynebacterium, Enterococcus, and Pseudomonas), and numerous MOs were negatively correlated with the symbiont Bifidobacterium. The neutral, nonfucosylated MO composed of eight hexoses had a positive relationship with SCC, while lactose had a negative relationship with SCC. One interpretation of these trends might be that in milk, MFAs disrupt primarily pathogenic bacterial cells, causing a relative increase in abundance of beneficial microbial taxa, while MOs respond to and act on pathogenic taxa primarily through antiadhesive methods. Further research is needed to confirm the potential mechanisms driving these correlations. IMPORTANCE Bovine milk can harbor microbes that cause mastitis, milk spoilage, and foodborne illness. Fatty acids found in milk can be antimicrobial and milk oligosaccharides can have antiadhesive, prebiotic, and immune-modulatory effects. Relationships among milk microbes, fatty acids, oligosaccharides, and inflammation have been reported for humans. To our knowledge, associations among the milk microbial composition, fatty acids, oligosaccharides, and lactose have not been reported for healthy lactating cows. Identifying these potential relationships in bovine milk will inform future efforts to characterize direct and indirect interactions of the milk components with the milk microbiota. Since many milk components are associated with herd management practices, determining if these milk components impact milk microbes may provide valuable information for dairy cow management and breeding practices aimed at minimizing harmful and spoilage-causing microbes in raw milk.

Reshaping the Binding Pocket of Cellobiose 2-Epimerase for Improved Substrate Affinity and Isomerization Activity for Enabling Green Synthesis of Lactulose

Enzymatic isomerization of lactose into lactulose via cellobiose 2-epimerase (CE) could provide an eco-friendly route for the industrial production of lactulose, a valuable food prebiotic. However, poor substrate affinity for lactose and preference for epimerization over isomerization hinder this application. Previous studies on CE improvement have focused on random mutagenesis or active site rational design; little is known about the relationship between substrate binding and enzyme efficacy, which was hence the subject of this study. First, residues 372W and 308W were identified as key for disaccharide recognition in CEs based on crystal structure alignment of the N-acetyl-glucosamine 2-epimerase superfamily and site-directed mutation. This binding domain was then reshaped through site saturation mutagenesis, resulting in seven mutants with enhanced isomerization activity. The optimal mutant CsCE/Q371E had significantly enhanced substrate affinity (K_m, 269.65 mM vs K_m, 417.5 mM), reduced epimerization activity, and 3.3-fold increased isomerization activity over the original CsCE. Molecular dynamics simulation further revealed that substituting Gln-371 with Glu strengthened the hydrogen-bonding network and altered the active site-substrate interactions, increasing the substrate stability and shifting the catalytic direction. This study uncovered new information about the substrate binding region and its mechanisms and impact on CE catalytic performance, paving the way for potential commercial applications.

Bifidobacterial β-Galactosidase-Mediated Production of Galacto-Oligosaccharides: Structural and Preliminary Functional Assessments

In the current study the ability of four previously characterized bifidobacterial β-galactosidases (designated here as BgaA, BgaC, BgaD, and BgaE) to produce galacto-oligosaccharides (GOS) was optimized. Of these enzymes, BgaA and BgaE were found to be promising candidates for GOS production (and the corresponding GOS mixtures were called GOS-A and GOS-E, respectively) with a GOS concentration of 19.0 and 40.3% (of the initial lactose), respectively. GOS-A and GOS-E were partially purified and structurally characterized. NMR analysis revealed that the predominant (non-lactose) disaccharide was allo-lactose in both purified GOS preparations. The predominant trisaccharide in GOS-A and GOS-E was shown to be 3′-galactosyllactose, with lower levels of 6′-galactosyllactose and 4′-galactosyllactose. These three oligosaccharides have also been reported to occur in human milk. Purified GOS-A and GOS-E were shown to be able to support bifidobacterial growth similar to a commercially available GOS. In addition, GOS-E and the commercially available GOS were shown to be capable of reducing Escherichia coli adhesion to a C2BBe1 cell line. Both in vitro bifidogenic activity and reduced E. coli adhesion support the prebiotic potential of GOS-E and GOS-A.

Composition analysis and oral administered effects on dextran sulfate sodium-induced colitis of galactooligosaccharides bioconverted by Bacillus circulans

Galactooligosaccharides have been known to have many health benefits as prebiotic ingredients. In this study, we examined the anti-inflammatory activity of the galactooligosaccharide, NeoGOS-P70 (Korean commercial product), in a dextran sodium sulfate-induced colitis model. Next, we performed compositional characterization of NeoGOS-P70, which confirmed that it was a 77.4% high-purity GOS products, including a large amount of 4'-galactosyllactose. Further experiments in DSS-induced colitis model showed that oral administration of NeoGOS-P70 could significantly improve DSS-induced colitis symptoms, such as weight loss, reduction in colon shortening, and suppression of inflammatory mediators, including interleukin-6, tumor necrosis factor-α, and myeloperoxidase secretion from colon of ulcerative colitis mice. Histological analysis of mucin expression in colon tissue revealed the protective effects of NeoGOS-P70. These results suggest the potential of the novel GOS, NeoGOS-P70, as an anti-ulcerative colitis agent that could regulate inflammatory responses.

Synthesis of magnetic nanoparticles functionalized with histidine and nickel to immobilize His-tagged enzymes using β-galactosidase as a model

The aim of this study was to synthesize iron magnetic nanoparticles functionalized with histidine and nickel (Fe₃O₄-His-Ni) to be used as support materials for oriented immobilization of His-tagged recombinant enzymes of high molecular weight, using β-galactosidase as a model. The texture, morphology, magnetism, thermal stability, pH and temperature reaction conditions, and the kinetic parameters of the biocatalyst obtained were assessed. In addition, the operational stability of the biocatalyst in the lactose hydrolysis of cheese whey and skim milk by batch processes was also assessed. The load of 600 U_enzyme/g_support showed the highest recovered activity value (~50%). After the immobilization process, the recombinant β-galactosidase (HisGal) showed increased substrate affinity and greater thermal stability (~50×) compared to the free enzyme. The immobilized β-galactosidase was employed in batch processes for lactose hydrolysis of skim milk and cheese whey, resulting in hydrolysis rates higher than 50% after 15 cycles of reuse. The support used was obtained in the present study without modifying chemical agents. The support easily recovered from the reaction medium due to its magnetic characteristics. The iron nanoparticles functionalized with histidine and nickel were efficient in the oriented immobilization of the recombinant β-galactosidase, showing its potential application in other high-molecular-weight enzymes.

Microbiota and Metabolite Modifications after Dietary Exclusion of Dairy Products and Reduced Consumption of Fermented Food in Young and Older Men

The gut microbiota adapts to age-related changes in host physiology but is also affected by environmental stimuli, like diet. As a source of both pre- and probiotics, dairy and fermented foods modulate the gut microbiota composition, which makes them interesting food groups to use for the investigation of interactions between diet and ageing. Here we present the effects of excluding dairy products and limiting fermented food consumption for 19 days on gut microbiota composition and circulating metabolites of 28 healthy, young (YA) and older (OA) adult men. The intervention affected gut microbial composition in both groups, with significant increases in Akkermansia muciniphila and decreases in bacteria of the Clostridiales order. Lower fasting levels of glucose and insulin, as well as dairy-associated metabolites like lactose and pentadecanoic acid, were observed after the intervention, with no effect of age. The intervention also decreased HDL and LDL cholesterol levels. Dairy fat intake was positively associated with the HDL cholesterol changes but not with the LDL/HDL ratio. In conclusion, restricting the intake of dairy and fermented foods in men modified their gut microbiota and blood metabolites, while the impact of the dietary restrictions on these outcomes was more marked than the effect of age.

Infant-Associated Bifidobacterial β-Galactosidases and Their Ability to Synthesize Galacto-Oligosaccharides

Galacto-oligosaccharides (GOS) represent non-digestible glycans that are commercially produced by transgalactosylation of lactose, and that are widely used as functional food ingredients in prebiotic formulations, in particular in infant nutrition. GOS consumption has been reported to enhance growth of specific bacteria in the gut, in particular bifidobacteria, thereby supporting a balanced gut microbiota. In a previous study, we assessed the hydrolytic activity and substrate specificity of seventeen predicted β-galactosidases encoded by various species and strains of infant-associated bifidobacteria. In the current study, we further characterized seven out of these seventeen bifidobacterial β-galactosidases in terms of their kinetics, enzyme stability and oligomeric state. Accordingly, we established whether these β-galactosidases are capable of synthesizing GOS via enzymatic transgalactosylation employing lactose as the feed substrate. Our findings show that the seven selected enzymes all possess such transgalactosylation activity, though they appear to differ in their efficiency by which they perform this reaction. From chromatography analysis, it seems that these enzymes generate two distinct GOS mixtures: GOS with a relatively short or long degree of polymerization profile. These findings may be the stepping stone for further studies aimed at synthesizing new GOS variants with novel and/or enhanced prebiotic activities and potential for industrial applications.

Recent approaches for the quantitative analysis of functional oligosaccharides used in the food industry: A review

Functional oligosaccharides (OS) are diverse groups of carbohydrates that confer several health benefits stemming from their prebiotic activity. Commonly used oligosaccharides, fructooligosaccharides and galactooligosaccharides, are used in a wide range of applications from food ingredients to mimic the prebiotic activity of human milk oligosaccharides (HMOs) in infant formula to sugar and fat replacers in dairy and bakery products. However, while consumption of these compounds is associated with several positive health effects, increased consumption can cause intestinal discomfort and aggravation of intestinal bowel syndrome symptoms. Hence, it is essential to develop rapid and reliable techniques to quantify OS for quality control and proper assessment of their functionality in food and food products. The present review will focus on recent analytical techniques used to quantify OS in different matrices such as food and beverage products.

Biotechnological approaches for the production of designer cheese with improved functionality

Cheese is a product of ancient biotechnological practices, which has been revolutionized as a functional food product in many parts of the world. Bioactive compounds, such as peptides, polysaccharides, and fatty acids, have been identified in traditional cheese products, which demonstrate functional properties such as antihypertensive, antioxidant, immunomodulation, antidiabetic, and anticancer activities. Besides, cheese-making probiotic lactic acid bacteria (LAB) exert a positive impact on gut health, aiding in digestion, and improved nutrient absorption. Advancement in biotechnological research revealed the potential of metabolite production with prebiotics and bioactive functions in several strains of LAB, yeast, and filamentous fungi. The application of specific biocatalyst producing microbial strains enhances nutraceutical value, resulting in designer cheese products with multifarious health beneficial effects. This review summarizes the biotechnological approaches applied in designing cheese products with improved functional properties.

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

Galacto-oligosaccharides (GOS) are prebiotic compounds widely used for their health-promoting effects. Conventionally, GOS is produced by the enzymatic conversion of lactose in stirred tank reactors (STR). The high operational costs associated with enzyme inactivation and removal might be reduced by the application of enzyme membrane reactors (EMR). In this study, we aimed to assess the potential of continuous GOS production by EMR using soluble Biolacta N5, a Bacillus circulans-derived commercial enzyme preparation. The steady-state performance of the EMR equipped with an ultrafiltration module was investigated as function of residence time (1.1-2.8 h) and enzyme load (17-190 U·g^-1) under fixed operational settings of temperature (50 °C), pH (6.0), lactose feed concentration (300 g·kg^-1), and recirculation flow-rate (0.18 m³·h^-1). Results indicate that the yield of oligosaccharides with higher degree of polymerization (DP3-6) in STR (approx. 38% on total carbohydrate basis) exceeds that measured in EMR (ranging from 24% to 33%). However, a stable catalytic performance without a significant deterioration in product quality was observed when operating the EMR for an extended period of time (> 120 h). Approx. 1.4 kg of DP3-6 was produced per one gram of crude enzyme preparation over the long-term campaigns, indicating that EMR efficiently recovers enzyme activity.

Synthesis of Butyl-β-D-Galactoside in the Ternary System: Acetone/1-Butanol/Aqueous Solution

The enzymatic synthesis of short-tailed alkyl glucosides is generally carried out in an aqueous-organic biphasic reaction medium with a rather low fatty alcohol concentration in the aqueous phase (where the synthesis occurs). Thus, hydrolytic reactions have a significant impact on the synthesis performance. Given this background, the use of acetone as cosolvent was studied for the synthesis of butyl-β-galactoside with Aspergillus oryzae β-galactosidase. The liquid-liquid equilibrium of the reaction mixture components (acetone/1-butanol/aqueous solution) was determined and the single- and two-phase regions were defined at 30, 40, and 50°C. It was observed that the liquid-liquid equilibrium of the ternary system acetone/1-butanol/water differs significantly from the one obtained using an aqueous solution (50 mM McIlvaine buffer pH 4.5; 5 g L^-1) instead of water. This is mainly because of the salting-out effect of the buffer; nevertheless, the presence of lactose also altered the equilibrium. Having this in mind, the effects of temperature (30 and 50°C) and reaction mixture composition were assessed. Three general conditions were evaluated: single-phase ternary system (30% acetone), two-phase ternary system (10% acetone) and two-phase binary system (0% acetone). Acetone had a deleterious effect on enzyme stability at 50°C, leading to low reaction yields. However, no enzyme deactivation was detected at 30°C. Moreover, a reaction yield of 0.98 mol mol^-1 was attained in the 30/50/20% (w/w) mixture of acetone/1-butanol/aqueous solution. This very high yield can be explained by the huge increase in the concentration of 1-butanol and the reduction of water activity. The synthesis was carried out using also the β-galactosidase immobilized in glyoxal-agarose and amino-glyoxal-agarose, and by aggregation and crosslinking. In the case of agarose-derived catalysts, two average particle diameters were assessed to evaluate the presence of internal mass transfer limitations. Best yield (0.88 mol mol^-1) was obtained with glyoxal-agarose derivatives and the particle size had non-effect on yield. The chemical structure of butyl-β-galactoside was determined by NMR and FT-IR.

Hydrolysis of Lactose and Transglycosylation of Selected Sugar Alcohols by LacA β-Galactosidase from Lactobacillus plantarum WCFS1

The production, biochemical characterization, and carbohydrate specificity of LacA β-galactosidase (locus lp_3469) belonging to the glycoside hydrolase family 42 from the probiotic organism Lactobacillus plantarum WCFS1 are addressed. The β-d-galactosidase activity was maximal in the pH range of 4.0-7.0 and at 30-37 °C. High hydrolysis capacity toward the β(1 → 4) linkages between galactose and glucose (lactose) or fructose (lactulose) was found. High efficiency toward galactosyl derivative formation was observed when lactose and glycerol, xylitol, or erythritol were used. Galactosyl derivatives of xylitol were characterized for the first time as 3-O-β-d-galactopyranosyl-xylitol and 1-O-β-d-galactopyranosyl-xylitol, displaying high preference of LacA β-galactosidase for the transfer of galactosyl residues from lactose to the C1 or C3 hydroxyl group of xylitol. These results indicate the feasibility of using LacA β-galactosidase for the synthesis of different galactosyl-polyols, which could be promising candidates for beneficial and appealing functional and technological applications such as novel prebiotics or hypocaloric sweeteners.

Prebiotic galactooligosaccharides production from lactose and lactulose by Lactobacillus delbrueckii subsp. bulgaricus CRL450

Galactooligosaccharides (GOS) are useful dietary ingredients recognized worldwide as prebiotics.

Application of Immobilized Enzymes in Food Industry

Enzymes are macromolecular biocatalysts, widely used in food industry. In applications, enzymes are often immobilized on inert and insoluble carriers, which increase their efficiency due to multiple reusability. The properties of immobilized enzymes depend on the immobilization method and the carrier type. The choice of the carrier usually concerns the biocompatibility, chemical and thermal stability, insolubility under reaction conditions, capability of easy regeneration and reusability, as well as cost efficiency. In this review, we provide an overview of various carriers for enzyme immobilization, with the primary focus on food industry.

Prospecting prebiotics, innovative evaluation methods, and their health applications: a review

Prebiotics are necessary natural and synthetic food ingredients that help in the growth and development of gut microflora. There is a complex relationship between gut dysbiosis and microbes, so alteration in both probiotics and prebiotics can reduce illness of gut, which further plays a decisive role in human health. The prebiotic efficiency can be validated using various in vitro and in vivo experiments, and this gives an important insight to this field. This review focuses on these aspects including the standardized assessment of prebiotics and its metabolic products for customary applications. This review has also summarized the mechanism of their beneficial actions such as immunomodulation, nutrient absorption, pathogen inhibition, etc., and its significance in human nutrition. In addition to this, some fascinating applications of prebiotics in health-related disorders have also discussed, with current challenges in this facet.

Sugar Protectants Improve the Thermotolerance and Biocontrol Efficacy of the Biocontrol Yeast, Candida oleophila

A variety of sugar compounds have been used as additives to protect various biocontrol yeasts from adverse environmental stresses. However, studies on maltose and lactose as sugar protectants are limited, and their protective effect is not clear. In the present study, exposure of the biocontrol yeast Candida oleophila cells to 45°C for 10 min, while immersed in either 5 or 10% (w/v) maltose or lactose, provided a significant protective effect. The addition of maltose and lactose significantly enhanced enzyme activity and gene expression of catalase, thioredoxin reductase, and glutathione reductase, relative to cells that have been immersed in sterile distilled water (controls) exposed to 45°C. In addition, C. oleophila cells suspended in maltose and lactose solutions also exhibited higher viability and ATP levels, relative to control cells. Notably, the biocontrol efficacy of C. oleophila against postharvest diseases of apple fruit was maintained after the yeast was exposed to the high temperature treatment while immersed in maltose and lactose solutions. These results demonstrate the potential of maltose and lactose as sugar protectants for biocontrol agent against heat stress.

Preparation and Characterization of Sugar-Assisted Cross-Linked Enzyme Aggregates (CLEAs) of Recombinant Cellobiose 2-epimerase from Caldicellulosiruptor saccharolyticus ( CsCE)

High-efficiency lactulose-producing enzyme of Caldicellulosiruptor saccharolyticus cellobiose 2-epimerase (WT- CsCE) was immobilized in the form of cross-linked enzyme aggregates (CLEAs). Conditions for enzyme aggregation and cross-linking were optimized, and a sugar-assisted strategy with less damage to enzyme secondary structures was developed to improve the activity yield of CLEAs up to approximately 65%. The resulting CLEAs with multiple-layer network structures exhibited an enlarged optimal temperature range (70-80 °C) and maintained higher activity at 50-90 °C. Besides, CLEAs retained more than 95% of their initial activity after 10 successive batches at 60 °C, demonstrating superior reusability. Moreover, CLEAs displayed an equivalent or higher catalytic ability to free WT- CsCE in lactulose biosynthesis, and the final sugar ratios were similar, lactulose 58.8-61.7%, epilactose 9.3-10.2%, and lactose 27.8-30%, with a constant isomerization selectivity of 0.84-0.87 regardless of enzymes used and temperature applied. The proposed strategy is the first trial for enzymatic synthesis of lactulose catalyzed by CLEAs of WT- CsCE.

Rapid changes in Atlantic grey seal milk from birth to weaning - immune factors and indicators of metabolic strain

True seals have the shortest lactation periods of any group of placental mammal. Most are capital breeders that undergo short, intense lactations, during which they fast while transferring substantial proportions of their body reserves to their pups, which they then abruptly wean. Milk was collected from Atlantic grey seals (Halichoerus grypus) periodically from birth until near weaning. Milk protein profiles matured within 24 hours or less, indicating the most rapid transition from colostrum to mature phase lactation yet observed. There was an unexpected persistence of immunoglobulin G almost until weaning, potentially indicating prolonged trans-intestinal transfer of IgG. Among components of innate immune protection were found fucosyllactose and siallylactose that are thought to impede colonisation by pathogens and encourage an appropriate milk-digestive and protective gut microbiome. These oligosaccharides decreased from early lactation to almost undetectable levels by weaning. Taurine levels were initially high, then fell, possibly indicative of taurine dependency in seals, and progressive depletion of maternal reserves. Metabolites that signal changes in the mother’s metabolism of fats, such as nicotinamide and derivatives, rose from virtual absence, and acetylcarnitines fell. It is therefore possible that indicators of maternal metabolic strain exist that signal the imminence of weaning.

Applications of prebiotics in food industry: A review

Benefits of prebiotics for stimulating a healthy intestinal tract are well known. From suppression of pathogens to proliferation of indigenous bacteria of intestines, prebiotics have it all. Since the research on the scope of prebiotics is expanding, new applications are coming up every day thus upgrading the choices consumer has for a healthy living. Incorporation of prebiotics in a wide range of products that food industry offers on shelf is an innovative way to replace fat and sugars along with enhancing the mouthfeel by providing better tongue lubrication. In some cases, the thermal stability of the product is improved along with other sensory, textural and physiological benefits. This paper gives an overview of the various prebiotics available from different sources and their applications in various segments of food industry, notably dairy, beverage, processed fruit-vegetable, bakery, confectionary, extruded snack, sweetener, infant formula, pet food and livestock industry. The effects observed on addition of various prebiotics are also elaborated.

Enzymatic Synthesis and Purification of Galactosylated Chitosan Oligosaccharides Reducing Adhesion of Enterotoxigenic Escherichia coli K88

Enterotoxigenic Escherichia coli (ETEC) K88 causes diarrhea in weaned piglets and represent a suitable model system for ETEC causing childhood diarrhea. This study aimed to evaluate the effects of oligosaccharides against ETEC K88 adhesion to porcine erythrocytes with two bioassays. Galactosylated chitosan-oligosaccharides (Gal-COS) were synthesized through transgalactosylation by β-galactosidase. Fractions 2-5 of Gal-COS were obtained through cation exchange and size exclusion chromatography. Fractions 2-5 of acetylated Gal-COS were obtained through chemical acetylation followed by size exclusion chromatography. Gal-COS F2 containing the largest oligosaccharides had the highest antiadhesion activity with the minimum inhibitory concentration of 0.22 g/L, followed by F3 and F4. Acetylation of Gal-COS decreased their ability to reduce ETEC K88 adhesion. The composition of active oligosaccharides was determined with LC-MS. Galactosylation of COS produces oligosaccharides which reduce ETEC K88 adhesion; moreover, resulting oligosaccharides match the composition of human milk oligosaccharides, which prevent adhesion of multiple pathogens.

Safety evaluation of galacto-oligosaccharides

Galacto-oligosaccharides (GOS) have been added to infant formulas and conventional foods as prebiotics all over the world. The present study was conducted to assess the subchronic toxicity of a GOS syrup (VITAGOS™) when administered orally by gavage daily at 0, 1020, 2041, and 4082 mg GOS syrup/kg/day to male and female Sprague-Dawley rats to deliver doses of 0, 500, 1000, and 2000 mg GOS/kg/day for 90 days. Throughout the entire treatment period, no abnormal clinical signs or mortalities were observed. Similarly, no test article-related toxicologically adverse findings were seen in body weight, feed consumption, ophthalmological findings, hematology, coagulation, clinical chemistry, urinalysis, organ weights, and gross pathology or histopathology. Significant increases in the cecum weight of males and females treated with 2000 mg GOS/kg/day were associated with mucosal hypertrophy/hyperplasia; no changes in the cecum were noted at lower doses. The organ weight and histopathological changes noted in the cecum are consistent with findings in rats administered other poorly digestible and fermentable substances; thus, this is considered to be an adaptive rather than toxic response. The No-Observed-Adverse-Effect-Levels for VITAGOS™ is 4082 mg GOS syrup/kg body weight/day or 2000 mg GOS/kg body weight/day.