Fructo-oligosaccharides: Production, Purification and Potential Applications

Investigating the Product Profiles and Structural Relationships of New Levansucrases with Conventional and Non-Conventional Substrates

The synthesis of complex oligosaccharides is desired for their potential as prebiotics, and their role in the pharmaceutical and food industry. Levansucrase (LS, EC 2.4.1.10), a fructosyl-transferase, can catalyze the synthesis of these compounds. LS acquires a fructosyl residue from a donor molecule and performs a non-Lenoir transfer to an acceptor molecule, via β-(2→6)-glycosidic linkages. Genome mining was used to uncover new LS enzymes with increased transfructosylating activity and wider acceptor promiscuity, with an initial screening revealing five LS enzymes. The product profiles and activities of these enzymes were examined after their incubation with sucrose. Alternate acceptor molecules were also incubated with the enzymes to study their consumption. LSs from Gluconobacter oxydans and Novosphingobium aromaticivorans synthesized fructooligosaccharides (FOSs) with up to 13 units in length. Alignment of their amino acid sequences and substrate docking with homology models identified structural elements causing differences in their product spectra. Raffinose, over sucrose, was the preferred donor molecule for the LS from Vibrio natriegens, N. aromaticivorans, and Paraburkolderia graminis. The LSs examined were found to have wide acceptor promiscuity, utilizing monosaccharides, disaccharides, and two alcohols to a high degree.

Engineering Yarrowia lipolytica for the Synthesis of Glutathione from Organic By-Products

Tripeptide glutathione, which plays important roles in many cellular mechanisms, is also a biotechnology-oriented molecule with applications in medicine, food and cosmetic. Here, the engineering of the yeast Yarrowia lipolytica for the production of this metabolite at high titer values from various agro-industrial by-products is reported. The constitutive overexpression of the glutathione biosynthetic genes GSH1 and GSH2 encoding respectively γ-glutamylcysteine synthetase and glutathione synthetase, together with the INU1 gene from Kluyveromyces marxianus encoding inulinase yielded a glutathione titer value and a productivity of 644 nmol/mg protein and 510 µmol/g_DCW, respectively. These values were obtained during bioreactor batch cultures in a medium exclusively comprising an extract of Jerusalem artichoke tuber, used as a source of inulin, and ammonium sulfate, used as a nitrogen source.

Microbial Medicine: Prebiotic and Probiotic Functional Foods to Target Obesity and Metabolic Syndrome

Obesity has become a global epidemic and a public health crisis in the Western World, experiencing a threefold increase in prevalence since 1975. High-caloric diets and sedentary lifestyles have been identified as significant contributors to this widespread issue, although the role of genetic, social, and environmental factors in obesity's pathogenesis remain incompletely understood. In recent years, much attention has been drawn to the contribution of the gut microbiota in the development of obesity. Indeed, research has shown that in contrast to their healthier counterparts the microbiomes of obese individuals are structurally and functionally distinct, strongly suggesting microbiome as a potential target for obesity therapeutics. In particular, pre and probiotics have emerged as effective and integrative means of modulating the microbiome, in order to reverse the microbial dysbiosis associated with an obese phenotype. The following review brings forth animal and human research supporting the myriad of mechanisms by which the microbiome affects obesity, as well as the strengths and limitations of probiotic or prebiotic supplementation for the prevention and treatment of obesity. Finally, we set forth a roadmap for the comprehensive development of functional food solutions in combatting obesity, to capitalize on the potential of pre/probiotic therapies in optimizing host health.

Whey and Its Derivatives for Probiotics, Prebiotics, Synbiotics, and Functional Foods: a Critical Review

The purpose of this review is to highlight the importance of whey as a source of new-generation functional ingredients. Particular interest is given to probiotic growth in the presence of whey derivatives such as lactulose, a lactose derivative, which is a highly sought-after prebiotic in functional feeding. The role of sugar/nitrogen interactions in the formation of Maillard products is also highlighted. These compounds are known for their antioxidant power. The role of bioactive peptides from whey is also discussed in this study. Finally, the importance of an integrated valuation of whey is discussed with an emphasis on functional nutrition and the role of probiotics in the development of novel foods such as synbiotics.

Removal of Small-Molecular Byproducts from Crude Fructo-Oligosaccharide Preparations by Fermentation Using the Endospore-Forming Probiotic Bacillus coagulans

Short-chain prebiotic fructo-oligosaccharides (FOS) produced by enzymatic conversion from sucrose often contains high concentration of monosaccharides as byproducts. In addition to conventional physical/chemical purification processes, microbial treatment is an alternative method to remove these byproducts. We used Bacillus coagulans to reduce the abundance of byproducts during the enzymatic production of FOS. It is a promising probiotic because this thermophilic and spore-forming bacterium remains viable and stable during food processing and storage. B. coagulans also produces lactic acid during the carbohydrate metabolism and is used industrially to produce lactic acid for medical and food/feed applications. We aimed to establish an evaluation system to screen different strains of B. coagulans for their performance and selected B. coagulans Thorne for the treatment of crude FOS due to its high growth rate, high sporulation rate, and low nutrient requirements. B. coagulans preferentially utilized monosaccharides over other sugar components of the FOS mixture. Glucose and fructose were completely consumed during the fermentation but 85% (w/w) of the total FOS remained. At the end of the fermentation, the total viable cell count of B. coagulans Thorne was 9.9 × 108 cfu·mL−1 and the maximum endospore count was 2.42 × 104 cfu·mL−1.

Optimation for preparation of oligosaccharides from flaxseed gum and evaluation of antioxidant and antitumor activities in vitro

Flaxseed oligosaccharides (FGOS) were prepared by degradation of flaxseed gum (FG) using enzymatic method. Factors affecting the enzymatic hydrolysis of FG were investigated by single factor and orthogonal tests. In the optimum hydrolysis conditions (reaction time 12 h, temperature 50 °C, pH 4.5, cellulase concentration 100 U/mL), the reducing sugar ratio and extraction yield of FGOS were 33.6 ± 0.35% and 56.8 ± 0.41%, respectively. The average molecular weight of FGOS was about 1.6 kDa, which consists of mannose, galactose, glucose, arabinose, glucuronic acid, xylose, rhamnose, ribose, galacturonic acid. Fourier-transform infrared spectra and NMR indicated that FG was successfully degraded to FGOS. FGOS exhibited better antioxidant activities than FG on scavenging hydroxyl, ABTS and DPPH radicals. In vitro cytotoxicities experiments reveal FGOS acquire the ability of antiproliferation against HepG2 and Hela cells in a dose-dependent manner.

Process development for the production of prebiotic fructo-oligosaccharides by penicillium citreonigrum

A new isolated P. citreonigrum URM 4459 was selected to produce fructooligosaccharides (FOS) in an efficient, economical and fast one-step fermentation. Optimal culture conditions were stablished by experimental design. Experiments run in bioreactor resulted in a high yield, content, productivity and purity of FOS (0.65 ± 0.06 g_FOS/g_{initial Sucrose}, 126.3 ± 0.1 g/L, 2.28 ± 0.08 g/L.h and 61 ± 0%). The FOS mixture was purified up to 92% (w/w) with an activated charcoal column. FOS produced were able to promote lactobacilli and bifidobacteria growth. Higher bacteria cell density was obtained for microbial-FOS mixtures than commercial Raftilose^® P95. Some strains grew even faster in the FOS mixture produced than in all other carbon sources. FOS were resistant to the simulated gastrointestinal conditions. A high amount of a reducing trisaccharide was identified in the FOS produced mixture, possibly neokestose, which may explain the great prebiotic potential of the FOS.

A new engineered endo-inulinase with improved activity and thermostability: Application in the production of prebiotic fructo-oligosaccharides from inulin

To construct a high-performance engineered endo-inulinase for fructo-oligosaccharides (FOS) production from inulin, an inulin binding module (IBM) was fused into either N- or C-terminal of an endo-inulinase. After heterologous expression, purification and characterization, the C-terminal fusion one (Eninu-IBM) with better activity, thermostability and inulin binding ability was employed for high-temperature in situ inulin hydrolysis in a 10-L fermentor. During this process, Eninu-IBM was first efficiently produced by the yeast cells at 28 °C for 96 h, and subsequently 1600 g unsterilized inulin per liter fermentation liquor was directly supplemented into the bioreactor for FOS production at 60 °C for 2 h. Finally, high purity of FOS (91.4%) were obtained with FOS titer, yield and productivity of 717.3 g/L, 0.912 g_FOS/g_Inulin and 358.6 g/L/h, respectively. The in vitro prebiotic assay indicated that the final FOS products with main polymerization degrees of 3-5 were preferably fermented by beneficial bifidobacteria and lactobacilli.

Lignocellulose derived functional oligosaccharides: production, properties, and health benefits

Lignocellulosic biomass (LB) is the renewable feedstock for the production of fuel/energy, feed/food, chemicals, and materials. LB could also be the versatile source of the functional oligosaccharides, which are non-digestible food ingredients having numerous applications in food, cosmetics, pharmaceutical industries, and others. The burgeoning functional food demand is expected to be more than US$440 billion in 2022. Because of higher stability at low pH and high temperature, oligosaccharides stimulate the growth of prebiotic bifidobacteria and lactic acid bacteria. Xylooligosaccharides (XOS) are major constituents of oligosaccharides consisting of 2-7 xylose monomeric units linked via β-(1,4)-linkages. XOS can be obtained from various agro-residues by thermochemical pretreatment, enzymatic or chemoenzymatic methods. While thermochemical methods are fast, reproducible, enzymatic methods are substrate specific, costly, and produce minimum side products. Enzymatic methods are preferred for the production of food grade and pharmaceutically important oligosaccharides. XOS are potent prebiotics having antioxidant properties and enhance the bio-adsorption of calcium and improving bowel functions, etc. LB can cater to the increasing demand of oligosaccharides because of their foreseeable amount and the advancements in technology to recover oligosaccharides. This paper summarizes the methods for oligosaccharides production from LB, classification, and benefits of oligosaccharides on human health.

Dietary fiber sources and human benefits: The case study of cereal and pseudocereals

Dietary fiber (DF) includes the remnants of the edible part of plants and analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the human large intestine. DF can be classified into two main groups according to its solubility, namely insoluble dietary fiber (IDF) that mainly consists on cell wall components, including cellulose, some hemicelluloses, lignin and resistant starch, and soluble dietary fiber (SDF) that consists of non-cellulosic polysaccharides as non-digestible oligosaccharides, arabinoxylans (AX), β-glucans, some hemicelluloses, pectins, gums, mucilages and inulin. The intake of DF is associated with health benefits. IDF can contribute to the normal function of the intestinal tract and it has an important role in the prevention of colonic diverticulosis and constipation. SDF is extensively fermented by gut microbiota and it is associated with carbohydrate and lipid metabolism, with important health benefits due to its hypocholesterolemic properties. Due to these nutritional and health properties, DF is widely used as functional ingredients in food industry, being whole grain cereals, pulses, fruits and vegetables the main sources of DF. Also some synthetic sources are employed, namely polydextrose, hydroxypropyl methylcellulose or cyclodextrins. The DF content of cereals varies depending on cultivars, their botanical components (pericarp, emdosperm and germ) and the processing conditions they have undergone (baking, extrusion, etc.). In cereal grains, AX are the predominant non-cellulose DF polysaccharides followed by cellulose and β-glucans, while in pseudocereals, pectins are quantitatively predominant.

Biotechnological applications of inulin-rich feedstocks

Inulin is a naturally occurring second largest storage polysaccharide with a wide range of applications in pharmaceutical and food industries. It is a robust polysaccharide which consists of a linear chain of β-2, 1-linked-d-fructofuranose molecules terminated with α-d-glucose moiety at the reducing end. It is present in tubers, bulbs and tuberous roots of more than 36,000 plants belonging to both monocotyledonous and dicotyledonous families. Jerusalem artichoke, chicory, dahlia, asparagus, etc. are important inulin-rich plants. Inulin is a potent substrate and inducer for the production of inulinases. Inulin/inulin-rich feedstocks can be used for the production of fructooligosaccharides and high-fructose syrup. Additionally, inulin-rich feedstocks can also be exploited for the production of other industrially important products like acetone, butanol, bioethanol, single cell proteins, single cell oils, 2, 3-butanediol, sorbitol, mannitol, etc. Current review highlights the biotechnological potential of inulin-rich feedstocks for the production of various industrially important products.

Amylases and related glycoside hydrolases with transglycosylation activity used for the production of isomaltooligosaccharides

Isomaltooligosaccharides (IMOS) are sugars with health promoting properties that make them relevant for the pharmaceutical and food industries. IMOS have ample chemical diversity achieved by different α-glucosidic linkages and polymerization degrees, forming linear, branched and cyclic structures. Enzymatic synthesis of these compounds can be carried out by glycoside hydrolases (GHs) with transglycosylating activity. Different substrates are used for the synthesis: combinations of disaccharides and monosaccharides, or polymeric carbohydrates such as starch or dextran, which are converted to IMOS by a combination of hydrolysis and transglucosylation. In this review, the structural features of different enzyme families (GH31, GH13, GH70, GH57 and GH66) involved in IMOS synthesis are analysed. Focus is placed on structural traits that affect substrate and product specificity, and on the relative efficiency of transglucosylation and hydrolysis. Information resulting from site-directed mutagenesis and sequence alignments complements structural data to understand the role of specific residues in the performance of the enzymes. Altogether, these studies provide a frame of knowledge which may be used to design new enzymes with improved properties

Annotation and De Novo Sequence Characterization of Extracellular β-Fructofuranosidase from Penicillium chrysogenum Strain HKF42

The genome of a fungal strain Penicillium chrysogenum strain HKF42, which can grow on 20% sucrose has been annotated for 7595 protein coding sequences. On mining of CAZymes, we could annotate a β-fructofuranosidase gene responsible for fructo-oligosaccharides (FOS) synthesis which is a known prebiotic. The enzyme activity was demonstrated and validated with the generation of FOS as kestose and nystose.

High level production of a recombinant acid stable exoinulinase from Aspergillus kawachii

Exoinulinases-enzymes extensively studied in recent decades because of their industrial applications-need to be produced in suitable quantities in order to meet production demands. We describe here the production of an acid-stable recombinant inulinase from Aspergillus kawachii in the Pichia pastoris system and the recombinant enzyme's biochemical characteristics and potential application to industrial processes. After an appropriate cloning strategy, this genetically engineered inulinase was successfully overproduced in fed-batch fermentations, reaching up to 840 U/ml after a 72-h cultivation. The protein, purified to homogeneity by chromatographic techniques, was obtained at a 42% yield. The following biochemical characteristics were determined: the enzyme had an optimal pH of 3, was stable for at least 3 h at 55 °C, and was inhibited in catalytic activity almost completely by Hg⁺². The respective K_m and V_max for the recombinant inulinase with inulin as substrate were 1.35 mM and 2673 μmol/min/mg. The recombinant enzyme is an exoinulinase but also possesses synthetic activity (i. e., fructosyl transferase). The high level of production of this recombinant plus its relevant biochemical properties would argue that the process presented here is a possible recourse for industrial applications in carbohydrate processing.

Optimization of simultaneously enzymatic fructo- and inulo-oligosaccharide production using co-substrates of sucrose and inulin from Jerusalem artichoke

Prebiotic substances are extracted from various plant materials or enzymatic hydrolysis of different substrates. The production of fructo-oligosaccharide (FOS) and inulo-oligosaccharide (IOS) was performed by applying two substrates, sucrose and inulin; oligosaccharide yields were maximized using central composite design to evaluate the parameters influencing oligosaccharide production. Inulin from Jerusalem artichoke (5-15% w/v), sucrose (50-70% w/v), and inulinase from Aspergillus niger (2-7 U/g) were used as variable parameters for optimization. Based on our results, the application of sucrose and inulin as co-substrates for oligosaccharide production through inulinase hydrolysis and synthesis is viable in comparative to a method using a single substrate. Maximum yields (674.82 mg/g substrate) were obtained with 5.95% of inulin, 59.87% of sucrose, and 5.68 U/g of inulinase, with an incubation period of 9 hr. The use of sucrose and inulin as co-substrates in the reaction simultaneously produced FOS and IOS from sucrose and inulin. Total conversion yield was approximately 67%. Our results support the high value-added production of oligosaccharides using Jerusalem artichoke, which is generally used as a substrate in prebiotics and/or bioethanol production.

Strain improvement and statistical optimization as a combined strategy for improving fructosyltransferase production by Aureobasidium pullulans NAC8

Strain improvement of a low fructosyltransferase-producing Aureobasidium pullulans NAC8 (Accession No. KX023301) was carried out using chemical mutagens such as ethidium bromide and ethyl methane sulfonate. The wild-type and mutant strain were distinguished using Random amplified polymorphic DNA PCR and DNA fingerprinting analysis. Plackett-Burman and Box Behnken design were statistical tools used to determine important media parameters and optimization, respectively. Phenotypically and genetically, the new improved strain was different from the wild-type. The most important media parameters from PDB influencing fructosyltransferase production were ammonium chloride, sucrose and yeast extract at p < 0.05. Some significant parameters obtained with the BBD exhibited quadratic effects on FTase. The F values (35.37 and 32.11), correlation coefficient (0.98 and 0.97) and the percent coefficient of variation (2.53% and 2.40%) were obtained for extracellular and intracellular FTase respectively. The validation of the model in the improved strain resulted in an overall 6.0 and 2.0-fold increase in extracellular and intracellular FTase respectively compared to the wild-type. A relatively low FTase-producing strain of Aureobasidium pullulans NAC8 was enhanced for optimum production using a two-pronged approach involving mutagenesis and statistical optimization. The improved mutant strain also had remarkable biotechnological properties that make it a suitable alternative than the wild-type.

Prebiotic Oligosaccharides: Special Focus on Fructooligosaccharides, Its Biosynthesis and Bioactivity

The bacterial groups in the gut ecosystem play key role in the maintenance of host's metabolic and structural functionality. The gut microbiota enhances digestion processing, helps in digestion of complex substances, synthesizes beneficial bioactive compounds, enhances bioavailability of minerals, impedes growth of pathogenic microbes, and prevents various diseases. It is, therefore, desirable to have an adequate intake of prebiotic biomolecules, which promote favorable modulation of intestinal microflora. Prebiotics are non-digestible and chemically stable structures that significantly enhance growth and functionality of gut microflora. The non-digestible carbohydrate, mainly oligosaccharides, covers a major part of total available prebiotics as dietary additives. The review describes the types of prebiotic low molecular weight carbohydrates, i.e., oligosaccharides, their structure, biosynthesis, functionality, and applications, with a special focus given to fructooligosaccharides (FOSs). The review provides an update on enzymes executing hydrolytic and fructosyltransferase activities producing prebiotic FOS biomolecules, and future perspectives.

Crystal structure of a β-fructofuranosidase with high transfructosylation activity from Aspergillus kawachii

β-Fructofuranosidases belonging to glycoside hydrolase family (GH) 32 are enzymes that hydrolyze sucrose. Some GH32 enzymes also catalyze transfructosylation to produce fructooligosaccharides. We found that Aspergillus kawachii IFO 4308 β-fructofuranosidase (AkFFase) produces fructooligosaccharides, mainly 1-kestose, from sucrose. We determined the crystal structure of AkFFase. AkFFase is composed of an N-terminal small component, a β-propeller catalytic domain, an α-helical linker, and a C-terminal β-sandwich, similar to other GH32 enzymes. AkFFase forms a dimer, and the dimerization pattern is different from those of other oligomeric GH32 enzymes. The complex structure of AkFFase with fructose unexpectedly showed that fructose binds both subsites −1 and +1, despite the fact that the catalytic residues were not mutated. Fructose at subsite +1 interacts with Ile146 and Glu296 of AkFFase via direct hydrogen bonds.

Highly Efficient Fructooligosaccharides Production by an Erythritol-Producing Yeast Yarrowia lipolytica Displaying Fructosyltransferase

Currently, fructooligosaccharides (FOS) are industrially transformed from sucrose by purified enzymes or fungi cells. However, these methods are expensive and time-consuming. An economical approach to producing FOS using erythritol-producing yeast cells was described in this study. Fructosyltransferase from Aspergillus oryzae was displayed on the cell surface of Yarrowia lipolytica, resulting in an engineered strain capable of transforming sucrose to FOS. An amount of 480 g/L FOS was produced within 3 h in a solution of 800 g/L sucrose and 5 g/L cells (dry cell weight, DCW) at pH 6.0 and 60 °C, with a yield of 60% of total sucrose and a productivity of 160 g/(L·h). The yeast pastes from the erythritol industry can be repeatedly used as the whole-cell catalysts at least 10 times by this newly developed approach. This efficient method is attractive for the large-scale production of FOS from sucrose.

Application of ultrasound for enhanced extraction of prebiotic oligosaccharides from selected fruits and vegetables

Ultrasound assisted extraction (UAE) was used to extract oligosaccharides from selected fruits (blueberry, nectarine, raspberry, watermelon) and vegetables (garlic, Jerusalem artichoke, leek, scallion, spring garlic and white onion). The individual fractions of the oligosaccharides were analyzed: 1-kestose (GF2), nystose (GF3) and 1F-β-fructofuranosylnystose (GF4) from the fructo-oligosaccharides (FOS), and raffinose and stachyose from the raffinose family oligosaccharides (RFO). Extraction parameters including solvent concentration (35-85% v/v), extraction temperature (25-50°C) and sonication time (5-15min) were examined using response surface methodology (RSM). Ethanol concentration of 63% v/v, temperature of 40°C and extraction time of 10min gave maximal concentration of the extracted oligosaccharides. The experimental values under optimal conditions were consistent with the predicted values. UAE increased the concentration of extracted oligosaccharides in all fruits and vegetables from 2 to 4-fold compared to conventional extraction. The highest increase of total oligosaccharides extracted by UAE was detected in Jerusalem artichoke, 7.17±0.348g/100gFW, compared to 1.62±0.094g/100gFW with conventional method.