Efficient Biosynthesis of Lactosucrose from Sucrose and Lactose by the Purified Recombinant Levansucrase from Leuconostoc mesenteroides B-512 FMC

Investigating the Potential of Phenolic Compounds and Carbohydrates as Acceptor Substrates for Levansucrase-Catalyzed Transfructosylation Reaction

This study characterizes the acceptor specificity of levansucrases (LSs) from Gluconobacter oxydans (LS1), Vibrio natriegens (LS2), Novosphingobium aromaticivorans (LS3), and Paraburkholderia graminis (LS4) using sucrose as fructosyl donor and selected phenolic compounds and carbohydrates as acceptors. Overall, V. natriegens LS2 proved to be the best biocatalyst for the transfructosylation of phenolic compounds. More than one fructosyl unit could be attached to fructosylated phenolic compounds. The transfructosylation of epicatechin by P. graminis LS4 resulted in the most diversified products, with up to five fructosyl units transferred. In addition to the LS source, the acceptor specificity of LS towards phenolic compounds and their transfructosylation products were found to greatly depend on their chemical structure: the number of phenolic rings, the reactivity of hydroxyl groups and the presence of aliphatic chains or methoxy groups. Similarly, for carbohydrates, the transfructosylation yield was dependent on both the LS source and the acceptor type. The highest yield of fructosylated-trisaccharides was Erlose from the transfructosylation of maltose catalyzed by LS2, with production reaching 200 g/L. LS2 was more selective towards the transfructosylation of phenolic compounds and carbohydrates, while reactions catalyzed by LS1, LS3 and LS4 also produced fructooligosaccharides. This study shows the high potential for the application of LSs in the glycosylation of phenolic compounds and carbohydrates.

Investigation of biocatalytic production of lactosucrose and fructooligosaccharides using levansucrases and dairy by-products as starting materials

Selected levansucrases (LSs) were investigated for their ability to catalyze the transfructosylation of lactose/sucrose into lactosucrose and fructooligosaccharides (FOSs). Additionally, dairy by-products, including whey permeate (WP) and milk permeate (MP), were assessed for their effectiveness as lactose sources. LSs from Gluconobacter oxydans (LS1), Vibrio natriegens (LS2), Novosphingobium aromaticivorans (LS3), and Burkholderia graminis (LS4) were utilized in three transfructosylation reactions that combined sucrose with either lactose, WP, or MP. All LSs demonstrated a higher transfructosylation activity than hydrolytic one, except for V. natriegens LS2 in the presence of sucrose and MP/sucrose. Furthermore, the bioconversion efficiency of lactose/sucrose into lactosucrose and FOSs exhibited varying time courses and end-product profiles. Both the acceptor specificity of LS and the thermodynamic equilibrium of its reaction modulated the end-product profile. V. natriegens LS2 resulted in the highest lactosucrose production of 328 and 251 g/L with lactose/sucrose and WP/sucrose, respectively. Our results revealed the potential of LS-catalyzed transfructosylation for the biocatalytic production of both lactosucrose and FOSs from abundant biomasses.

Biosynthesis of lactosucrose by a new source of β-fructofuranosidase from Bacillus methanolicus LB-1

Lactosucrose (LS) is a prebiotic trisaccharide enzymatically synthesized by transglycosylation from lactose and sucrose with beneficial health effect. The β-fructofuranosidase used for synthesis of LS was produced from Bacillus methanolicus LB-1, which was isolated from traditional rice wine. A maximal yield of 8.63 U/mL of the enzyme was obtained by fermentation with B. methanolicus LB-1 under the optimized conditions: 10 g/L of glucose, 5 g/L of yeast extract, initial medium pH at 7.0, 37 °C, 24 h. The enzyme was purified and identified by ammonium sulfate fractional precipitation, Sephadex G-75 gel filtration chromatography and LC-MS, and SDS-PAGE of the purified enzyme showed a major protein band at 45 kDa. Biosynthesis of LS was performed using the purified β-fructofuranosidase, and production of LS reached 110 g/L under the optimized reaction conditions: pH at 7.0, 37 °C, 6.0 U/g sucrose of enzyme, 15% of sucrose, 15% of lactose, 28 h. HPLC analysis of the reaction products showed a distinct peak for LS at about 30 min of elution, confirming that B. methanolicus LB-1 β-fructofuranosidase had effective transfructosylation activity. Therefore, this new microbial source of β-fructofuranosidase may be a candidate with potential application prospect in biosynthesis of prebiotic LS.

Prebiotics as a Tool for the Prevention and Treatment of Obesity and Diabetes: Classification and Ability to Modulate the Gut Microbiota

Diabetes and obesity are metabolic diseases that have become alarming conditions in recent decades. Their rate of increase is becoming a growing concern worldwide. Recent studies have established that the composition and dysfunction of the gut microbiota are associated with the development of diabetes. For this reason, strategies such as the use of prebiotics to improve intestinal microbial structure and function have become popular. Consumption of prebiotics for modulating the gut microbiota results in the production of microbial metabolites such as short-chain fatty acids that play essential roles in reducing blood glucose levels, mitigating insulin resistance, reducing inflammation, and promoting the secretion of glucagon-like peptide 1 in the host, and this accounts for the observed remission of metabolic diseases. Prebiotics can be either naturally extracted from non-digestible carbohydrate materials or synthetically produced. In this review, we discussed current findings on how the gut microbiota and microbial metabolites may influence host metabolism to promote health. We provided evidence from various studies that show the ability of prebiotic consumption to alter gut microbial profile, improve gut microbial metabolism and functions, and improve host physiology to alleviate diabetes and obesity. We conclude among other things that the application of systems biology coupled with bioinformatics could be essential in ascertaining the exact mechanisms behind the prebiotic–gut microbe–host interactions required for diabetes and obesity improvement.

Comprehensive utilization of sucrose resources via chemical and biotechnological processes: A review

Sucrose, one of the most widespread disaccharides in nature, has been available in daily human life for many centuries. As an abundant and cheap sweetener, sucrose plays an essential role in our diet and the food industry. However, it has been determined that many diseases, such as obesity, diabetes, hyperlipidemia, etc., directly relate to the overconsumption of sucrose. It arouses many explorations for the conversion of sucrose to high-value chemicals. Production of valuable substances from sucrose by chemical methods has been studied since a half-century ago. Compared to chemical processes, biotechnological conversion approaches of sucrose are more environmentally friendly. Many enzymes can use sucrose as the substrate to generate functional sugars, especially those from GH68, GH70, GH13, and GH32 families. In this review, enzymatic catalysis and whole-cell fermentation of sucrose for the production of valuable chemicals were reviewed. The multienzyme cascade catalysis and metabolic engineering strategies were addressed.

Efficient biosynthesis of lacto-N-neotetraose by a novel β-1,4-galactosyltransferase from Aggregatibacter actinomycetemcomitans NUM4039

Lacto-N-neotetraose (LNnT) is a unique tetrasaccharide naturally occurring in human milk, as an important member of human milk oligosaccharides. Because of promising beneficial effects, it has been commercially added as a functional fortifier in infant formula. β-1,4-Galactosyltransferase (β-1,4-GalT) catalyzes LNnT biosynthesis from uridine 5'-diphospho-galactose (UDP-Gal) to lacto-N-triose II (LNT II). There have been only two LNnT-producing bacterial β-1,4-GalTs, including the ones from Neisseria meningitidis and Histophilus somni. In this study, a novel LNnT-producing β-1,4-GalT was identified from Aggregatibacter actinomycetemcomitans. The enzyme was easily overexpressed in E. coli in soluble form. It displayed much higher transglycosylation versus hydrolysis activity, indicating its great potential in LNnT biosynthesis. The enzyme produced 13 mM LNnT from 20 mM LNT II and 60 mM UDP-Gal, with the yield of 65 % on LNT II and very low level of UDP-Gal hydrolysis. Therefore, it could be considered as a good candidate for the practical LNnT production.

Biocatalytic synthesis of lactosucrose using a recombinant thermostable β-fructofuranosidase from Arthrobacter sp. 10138

As a prebiotics, lactosucrose plays an important role in maintaining human gastrointestinal homeostasis. In this study, a thermostable enzyme from Arthrobacter sp. 10138 was screened from six β-fructofuranosidase-producing strains for the lactosucrose production and the coding gene was heterologously expressed in Escherichia coli for efficient expression. Recombinant β-fructofuranosidase was purified and biochemically characterized by MALDI-TOFMS spectrometry. The transfructosylation product by this recombinant enzyme was determined to be lactosucrose rather than other oligosaccharides or polysaccharides by HPLC and LC-MS. Efficient extracellular secretion of β-fructofuranosidase was achieved by the optimization of signal peptide and induction conditions. It was found that with the signal peptide torT, the highest extracellular activity reached 111.01 U/mL, which was 38.4-fold higher than that with the OmpA signal peptide. Under the optimal conditions (pH 6.0, temperature 50°C, enzyme amount 40 μg/ml, sucrose 150 g/L and lactose 150 g/L), 109 g/L lactosucrose was produced with a molar conversion ratio of 49.3%. Here the thermostable β-fructofuranosidase from Arthrobacter sp. 10138 can be used for efficient synthesis of lactosucrose, and this provides a good startpoint for the industrial production of lactosucrose in the future.

Effective production of lactosucrose using β-fructofuranosidase and glucose oxidase co-immobilized by sol-gel encapsulation

The production of lactosucrose is hampered by the costly use of β-fructofuranosidase, which shows poor stability and a low efficiency in transfructosylation activity. Immobilization could improve enzyme stability and realize the cyclic utilization at a reduced cost. In order to eliminate the by-product inhibition and improve the transfructosylation efficiency, β-fructofuranosidase and glucose oxidase were co-immobilized by sol-gel encapsulation and the subsequent production efficiency of lactosucrose was investigated. The as-prepared immobilized bi-enzymes retained 85.39% of their initial activity at an enzyme concentration of 1.47 mg/g·sol during immobilization and showed great operational stability (maintaining 78.5% of their initial activity) after 15 consecutive reuses. The yield of lactosucrose synthesized by immobilized bi-enzymes reached 160.8 g/L under the optimized conditions, which was relatively higher than previous reported results. Moreover, the yield of lactosucrose synthesized by immobilized bi-enzymes was significantly improved as compared to that synthesized by immobilized β-fructofuranosidase. HPLC and NMR spectrum results confirmed the presence of lactosucrose during immobilized bi-enzymes catalysis. Furthermore, a relatively high purity of lactosucrose was obtained (87.4% determined by HPLC) after separation with Diaion UBK535 calcium ester resin, and the optimal conditions for separation of lactosucrose were investigated. These results indicated that the co-immobilization of β-fructofuranosidase-glucose oxidase was helpful to improve the production of lactosucrose with low costs, which can be used in continuous lactosucrose production in food industry in advantages of high stability and reusability. And the as-prepared lactosucrose with high purity can be applied to many kinds of food as functional additives.

Enzymatic Production of Melibiose from Raffinose by the Levansucrase from Leuconostoc mesenteroides B-512 FMC

Melibiose, which is an important reducing disaccharide formed by α-1,6 linkage between galactose and glucose, has been proven to have beneficial applications in both medicine and agriculture. In this study, a characterized levansucrase from Leuconostoc mesenteroides B-512 FMC was further used to study the bioproduction of melibiose from raffinose. The reaction conditions were optimized for melibiose synthesis. The optimal pH, temperature, substrate concentration, ratio of substrates, and units of enzymes were determined as pH 6.0, 45 °C, 210 g/L, 1:1 (210 g/L:210 g/L), and 5 U/mL, respectively. The transfructosylation product of raffinose was determined to be melibiose by FTIR and NMR. A high raffinose concentration was found to strongly favor the production of melibiose. When 210 g/L raffinose and 210 g/L lactose were catalyzed using 5 U/mL purified levansucrase at pH 6.0 and 45 °C, the maximal yield of melibiose was 88 g/L.