Structural Elucidation of Enzymatically Synthesized Galacto-oligosaccharides Using Ion-Mobility Spectrometry-Tandem Mass Spectrometry

Evaluation of Prebiotic Properties of Galactooligosaccharides Produced by Transgalactosylation Using Partially Purified β-Galactosidase from Enterobacter aerogenes KCTC2190

Transgalactosylation reaction is the penultimate step in the production of galactooligosaccharides (GOSs) which has prominent applications in the treatment of disorders. In the present study, partially purified β-galactosidase from Enterobacter aerogenes KCTC2190 was used for the synthesis of prebiotic GOSs. GOSs were produced using lactose as substrate. Structural elucidation of collected fractions of GOSs by liquid chromatography electrospray ionization mass spectrometry exhibited the appearance of major peaks of produced GOSs at m/z 241.20, 481.39, 365.11, 527.17, and 701.51 respectively. GOSs facilitated the growth of potential probiotic strains (Lactobacillus delbrueckii ssp. helveticus, Bifidobacterium bifidum, and Lactiplantibacillus plantarum) and liberated propionate and butyrate as principal short-chain fatty acids which established its prebiotic potency. Synbiotic combinations exhibited good antioxidant activities. Synbiotic combinations also exhibited antimicrobial activities against pathogenic microorganisms namely Staphylococcus aureus and Escherichia coli. Synbiotic combinations of GOSs and the respective probiotic microorganisms were able to decrease viable human bone cancer cells (MG-63).

Structure and function of non-digestible carbohydrates in the gut microbiome

Together with proteins and fats, carbohydrates are one of the macronutrients in the human diet. Digestible carbohydrates, such as starch, starch-based products, sucrose, lactose, glucose and some sugar alcohols and unusual (and fairly rare) α-linked glucans, directly provide us with energy while other carbohydrates including high molecular weight polysaccharides, mainly from plant cell walls, provide us with dietary fibre. Carbohydrates which are efficiently digested in the small intestine are not available in appreciable quantities to act as substrates for gut bacteria. Some oligo- and polysaccharides, many of which are also dietary fibres, are resistant to digestion in the small intestines and enter the colon where they provide substrates for the complex bacterial ecosystem that resides there. This review will focus on these non-digestible carbohydrates (NDC) and examine their impact on the gut microbiota and their physiological impact. Of particular focus will be the potential of non-digestible carbohydrates to act as prebiotics, but the review will also evaluate direct effects of NDC on human cells and systems.

An improved method for galactosyl oligosaccharide characterization

Due to beneficial effects of galactosyl oligosaccharides (GOS) on digestive and immune health, their characterization has become increasingly important. This is especially so as GOS are synthesized enzymatically and contain oligosaccharides of different sizes and linkages. High performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) is widely used for GOS characterization. With its high resolving power, it can separate structural isomers. Here we present a significant improvement to currently used methods. Our approach combines high resolution HPAE separation on a CarboPac PA300 column with 4 µm particle size with PAD and Orbitrap mass spectrometry (MS) detections to provide in-depth information on GOS composition. Oligosaccharide resolution, especially in the disaccharide region, is significantly improved and can be routinely achieved. Improvement in technology to remove sodium before MS results in minimal peak dispersion, allowing GOS degrees of polymerization 2 to 6 to be identified based on mass spectra obtained from intact oligosaccharides and confirmed using fragmentation patterns observed in MS/MS data. Combining HPAE with MS led to identification of 28 oligosaccharides in a commercial GOS sample. We attempted to correlate oligosaccharide structure with observed elution behavior. To our knowledge this is first such attempt and can form a basis for a comprehensive structure vs HPAE elution behavior database.

Characterization of galacto-oligosaccharides using high-performance anion exchange chromatography-tandem mass spectrometry

The analysis of complex oligosaccharide mixtures remains a challenge in the field of analytical chemistry. In this work, two commercial galacto-oligosaccharides samples were characterized using high-performance anion exchange chromatography coupled to mass spectrometry. The isomeric oligosaccharides were resolved with high resolution. The structures of the individual isomers with a degree of polymerization up to 6 were analyzed using targeted selected ion monitoring with data-dependent tandem mass spectrometry, with additional in-source collision-induced dissociation.

Detection of galactooligosaccharides with high lactose interference in infant formula using a simple single epimer chromatography

Robust and more anti-interference enzymatic quantification of galactooligosaccharide (GOS) is important in consumer protection. However, many methods with harsh conditions could hardly separate GOS's hydrolysates galactose from its structurally similar isomer glucose, since each of them has double epimers, especially to determinate a trace of GOS from large amounts of lactose in the food matrix. The investigation was designed to solve the problem by using High Performance Liquid Chromatography with Evaporative Light Scattering Detector (HPLC-ELSD), applying friendly mobile phase and column. Result showed the content of galactose was seldom affected even by a high content of glucose by integrating the peak area of an excellent resolution single epimer. Moreover, the method existed a good linearity and stability (recovery rate at 90.5-105.1%), which met the statutory limit requirement for the quantitative analysis of concentrated GOS in infant formula. It was also helpful for separating and quantifying other sugar or epimers.

Isomer Information from Ion Mobility Separation of High-Mannose Glycan Fragments

Extracted arrival time distributions of negative ion CID-derived fragments produced prior to traveling-wave ion mobility separation were evaluated for their ability to provide structural information on N-linked glycans. Fragmentation of high-mannose glycans released from several glycoproteins, including those from viral sources, provided over 50 fragments, many of which gave unique collisional cross-sections and provided additional information used to assign structural isomers. For example, cross-ring fragments arising from cleavage of the reducing terminal GlcNAc residue on Man₈GlcNAc₂ isomers have unique collision cross-sections enabling isomers to be differentiated in mixtures. Specific fragment collision cross-sections enabled identification of glycans, the antennae of which terminated in the antigenic α-galactose residue, and ions defining the composition of the 6-antenna of several of the glycans were also found to have different cross-sections from isomeric ions produced in the same spectra. Potential mechanisms for the formation of the various ions are discussed and the estimated collisional cross-sections are tabulated. Graphical Abstract ᅟ.

Contemporary glycomic approaches using ion mobility-mass spectrometry

Characterization of complex oligosaccharides has historically required extensive sample handling and separations before analysis using nuclear magnetic resonance spectroscopy and electron impact mass spectra following hydrolysis, derivatization, and gas chromatographic separation. Advances in liquid chromatography separations and tandem mass spectrometry have expanded the range of intact glycan analysis, but carbohydrate structure and conformation-integral chemical characteristics-are often difficult to assess with minimal amounts of sample in a rapid fashion. Because ion mobility spectrometry (IMS) separates analytes based upon an effective 'size-to-charge' ratio, IMS is, by extension, highly applicable to glycomics. Furthermore, the speed of IMS, its growing levels of separation efficiency, and direct compatibility with all forms of mass spectrometry, illustrates is core role in the future of glycomics efforts. This review assesses the current state of ion mobility-mass spectrometry applied to glycan, glycoprotein, and glycoconjugate analysis. Currently, assessing optimal ion polarity and adduct type for a glycan class along with the appropriate tandem mass spectrometry technique underpin many of the current glycan analysis efforts using ion mobility-mass spectrometry (IMMS). Once determined, these parameters have enabled a growing and impressive range of glycomics campaigns employing this technique. Additionally, the combination of IMS with tandem mass spectrometry, and even spectroscopic methods, further expands the dimensionality of hybrid instrumentation to provide a more comprehensive assessment of glycan structure across a wide dynamic range. Continued computational efforts to complement experimental and instrumental advancements also serve as a core component of IMMS workflows applied to glycomics and promise to maximize the information gained from mobility separations.

Comprehensive characterization of ethoxyquin transformation products in fish feed by traveling-wave ion mobility spectrometry coupled to quadrupole time-of-flight mass spectrometry

Feed additives are typically used in intensive farming production over long periods, and hence, they can accumulate in farmed animal tissues. Concerns regarding the use of ethoxyquin as an antioxidant feed additive, have recently arisen due to its potential conversion into a series of transformation products (TPs). The aim of this work was to characterize the TPs of ethoxyquin in fish feed by a novel approach based on the use of traveling-wave ion mobility spectrometry (TWIMS) coupled to high-resolution quadrupole time-of-flight mass spectrometry (QTOFMS). First, ethoxyquin was oxidized under controlled conditions and the generated TPs were added to a comprehensive database. Atlantic salmon feeds were then screened for ethoxyquin TPs using both targeted and untargeted approaches. Twenty-seven TPs were tentatively identified during the oxidation experiments, fifteen of them also being present in the feed samples. In addition, ten other potential TPs were detected in fish feed following the untargeted approach. Thirty-one of these TPs have been reported for the first time in this work through the oxidation experiments and the feed samples. Therefore, this study provides valuable information on the oxidative fate of ethoxyquin in feed, which can be used for future evaluations of potential risk related to this additive.

Ion-Mobility-Derived Collision Cross Section as an Additional Identification Point for Multiresidue Screening of Pesticides in Fish Feed

Ion mobility spectrometry allows for the measurement of the collision cross section (CCS), which provides information about the shape of an ionic molecule in the gas phase. Although the hyphenation of traveling-wave ion mobility spectrometry (TWIMS) with high-resolution quadrupole time-of-flight mass spectrometry (QTOFMS) has been mainly used for structural elucidation purposes, its potential for fast screening of small molecules in complex samples has not yet been thoroughly evaluated. The current work explores the capabilities of ultrahigh-performance liquid chromatography (UHPLC) coupled to a new design TWIMS-QTOFMS for the screening and identification of a large set of pesticides in complex salmon feed matrices. A database containing TWIMS-derived CCS values for more than 200 pesticides is hereby presented. CCS measurements showed high intra- and interday repeatability (RSD < 1%), and they were not affected by the complexity of the investigated matrices (ΔCCS ≤ 1.8%). The use of TWIMS in combination with QTOFMS was demonstrated to provide an extra-dimension, which resulted in increased peak capacity and selectivity in real samples. Thus, many false-positive detections could be straightforwardly discarded just by applying a maximum ΔCCS tolerance of ±2%. CCS was proposed as a valuable additional identification point in the pesticides screening workflow. Several commercial fish feed samples were finally analyzed to demonstrate the applicability of the proposed approach. Ethoxyquin and pirimiphos-methyl were identified in most of the analyzed samples, whereas tebuconazole and piperonil butoxide were identified for the first time in fish feed samples.

Novel β-galactosidase nanobiocatalyst systems for application in the synthesis of bioactive galactosides

Amino modified nonporous fumed nano-silica particles was used for the development of efficient nanobiocatalysts for application in the biosynthesis of bioactive galactosides, galacto-oligosaccharides (GOS).