Sugar Alcohol Metabolism Research Articles

Untargeted metabolomic profiling of Aspergillus sojae 3.495 and Aspergillus oryzae 3.042 fermented soy sauce koji and effect on moromi fermentation flavor

Aspergillus sojae 3.495 and Aspergillus oryzae 3.042 are essential microbial starters in fermented foods due to their high hydrolytic enzyme activities. However, their metabolic characteristics and differences during soy sauce fermentation are still unclear. This study identified 42 non-volatile differential metabolites based on UHPLC-MS/MS, among which 10 amino acids and derivatives and 4 non-volatile acids were high in A. sojae 3.495 koji, while 3 sugar alcohols, 5 flavonoids, and 4 fatty acids were prominent in A. oryzae 3.042. Further analysis revealed that higher acidic protease (1887.43 U/g) in A. sojae 3.495 and higher glucoamylase (2413.36 U/g) and cellulase (890.78 U/g) in A. oryzae 3.042 dominated the formation of differential metabolites. Metabolic pathway analysis showed that shikimate and phenylalanine metabolic pathways in A. sojae 3.495 were more active and enhanced 3-methyl-butanal and 2-phenylethanal in moromi fermentation. The more prominent pathways of sugar alcohol metabolism and flavonoid biosynthesis in A. oryzae 3.042 koji enhanced 2-methyl-butanoic acid and ethyl 3-methylbutyrate in moromi and significantly elevated reducing sugars (1.56 g/100 mL). Overall, comparative metabolomics elucidated the metabolic framework and flavor formation mechanisms of different inocula in soy sauce koji, providing ideas for scientific control of soy sauce fermentation and multi-strain koji-making for flavor enhancement.

Comparative metabolomics of root-tips reveals distinct metabolic pathways conferring drought tolerance in contrasting genotypes of rice

BackgroundThe mechanisms underlying rice root responses to drought during the early developmental stages are yet unknown.ResultsThis study aimed to determine metabolic differences in IR64, a shallow-rooting, drought-susceptible genotype, and Azucena, a drought-tolerant and deep-rooting genotype under drought stress. The morphological evaluation revealed that Azucena might evade water stress by increasing the lateral root system growth, the root surface area, and length to access water. At the same time, IR64 may rely mainly on cell wall thickening to tolerate stress. Furthermore, significant differences were observed in 49 metabolites in IR64 and 80 metabolites in Azucena, for which most metabolites were implicated in secondary metabolism, amino acid metabolism, nucleotide acid metabolism and sugar and sugar alcohol metabolism. Among these metabolites, a significant positive correlation was found between allantoin, galactaric acid, gluconic acid, glucose, and drought tolerance. These metabolites may serve as markers of drought tolerance in genotype screening programs. Based on corresponding biological pathways analysis of the differentially abundant metabolites (DAMs), biosynthesis of alkaloid-derivatives of the shikimate pathway, fatty acid biosynthesis, purine metabolism, TCA cycle and amino acid biosynthesis were the most statistically enriched biological pathway in Azucena in drought response. However, in IR64, the differentially abundant metabolites of starch and sucrose metabolism were the most statistically enriched biological pathways.ConclusionMetabolic marker candidates for drought tolerance were identified in both genotypes. Thus, these markers that were experimentally determined in distinct metabolic pathways can be used for the development or selection of drought-tolerant rice genotypes.

Versatile roles of sorbitol in higher plants: luxury resource, effective defender or something else?

Sorbitol metabolism plays multiple roles in many plants, including energy and carbon enrichment, effective defence against various stresses and other emerging specific roles. The underlying mechanisms are, however, incompletely understood. This review provides the current state-of-the-art, highlights missing knowledge and poses several remaining questions. The basic properties of sugar alcohols are summarised and pathways of sorbitol metabolism, including biosynthesis, degradation and key enzymes are described. Sorbitol transport within the plant body is discussed and individual roles of sorbitol in different organs, specific cells or even cellular compartments, are elaborated, clarifying the critical importance of sorbitol allocation and distribution. In addition to plants that accumulate and transport significant quantities of sorbitol (usual producers), there are some that synthesize small amounts of sorbitol or only possess sorbitol metabolising enzymes (non-usual producers). Modern analytical methods have recently enabled large amounts of data to be acquired on this topic, although numerous uncertainties and questions remain. For a long time, it has been clear that enriching carbohydrate metabolism with a sorbitol branch improves plant fitness under stress. Nevertheless, this is probably valid only when appropriate growth and defence trade-offs are ensured. Information on the ectopic expression of sorbitol metabolism genes has contributed substantially to our understanding of the sorbitol roles and raises new questions regarding sorbitol signalling potential. We finally examine strategies in plants producing sorbitol compared with those producing mannitol. Providing an in-depth understanding of sugar alcohol metabolism is essential for the progress in plant physiology as well as in targeted, knowledge-based crop breeding.

Efficiency of Bacillus subtilis metabolism of sugar alcohols governs its probiotic effect against cariogenic Streptococcus mutans

Bacillus subtilis is a Gram-positive probiotic bacterium that successfully colonises plant roots due to its ability to utilise various sugars. The vast probiotic potential of B. subtilis has been recently demonstrated in numerous host organisms under different environmental conditions. We examined the probiotic potential of B. subtilis against the pathogenic bacterium Streptococcus mutans, which is involved in various oral disorders due to its robust biofilm-forming capability. B. subtilis cells attenuated biofilm formation by S. mutans during their dual growth in the presence of sugar alcohols. Transcription of genes encoding key enzymes in the metabolism of sugar alcohols by B. subtilis were highly induced. Moreover, growth-curve analysis suggested that B. subtilis is more efficient at early utilising sugar alcohols than S. mutans, as supported by the bacterial metabolic activity rates. Similarly, a comparison of secondary metabolites of mono and mixed cultures of B. subtilis and S. mutans indicated that B. subtilis is more active metabolically in the dual culture. Finally, knock-out mutations of the genes encoding key enzymes in the central metabolic pathway significantly reduced B. subtilis' ability to mitigate biofilm formation by S. mutans. We conclude that effective metabolism of sugar alcohols by B. subtilis reinforces the probiotic potential of this bacterium against pathogenic species such as S. mutans.

Metabolomics and physiological analyses reveal β-sitosterol as an important plant growth regulator inducing tolerance to water stress in white clover

β-sitosterol influences amino acids, carbohydrates, organic acids, and other metabolite metabolism and homeostasis largely contributing to better tolerance to water stress in white clover. β-sitosterol (BS) could act as an important plant growth regulator when plants are subjected to harsh environmental conditions. Objective of this study was to examine effects of BS on growth and water stress tolerance in white clover based on physiological responses and metabolomics. White clover was pretreated with or without BS and then subjected to water stress for 7days in controlled growth chambers. Physiological analysis demonstrated that exogenous application of BS (120μM) could significantly improve stress tolerance associated with better growth performance and photosynthesis, higher leaf relative water content, and less oxidative damage in white clover in response to water stress. Metabolic profiling identified 78 core metabolites involved in amino acids, organic acids, sugars, sugar alcohols, and other metabolites in leaves of white clover. For sugars and sugar alcohol metabolism, the BS treatment enhanced the accumulation of fructose, glucose, maltose, and myo-inositol contributing to better antioxidant capacity, growth maintenance, and osmotic adjustment in white clover under water stress. The application of BS was inclined to convert glutamic acid into proline, 5-oxoproline, and chlorophyll instead of going to pyruvate and alanine; the BS treatment did not significantly affect intermediates of tricarboxylic acid cycle (citrate, aconitate, and malate), but promoted the accumulation of other organic acids including lactic acid, glycolic acid, glyceric acid, shikimic acid, galacturonic acid, and quinic acid in white clover subjected to water stress. In addition, cysteine, an important antioxidant metabolite, was also significantly improved by BS in white clover under water stress. These altered amino acids and organic acids metabolism could play important roles in growth maintenance and modulation of osmotic and redox balance against water stress in white clover. Current findings provide a new insight into BS-induced metabolic homeostasis related to growth and water stress tolerance in plants.

Understanding metabolic processes shaping adaptation of E. coli to the gut

Many microbes colonise the gut establishing interactions with their host and their nutritional environment. Studying genetics and metabolism brought about the drive and potential to engineer communities to promote health and improve industrial processes. However, structuring artificial communities in predictable ways is underdeveloped. We studied Escherichia coli’s genetic targets and physiological mechanisms during gut colonisation and adaptation and how metabolic environment/microbiota complexity shape these processes. We introduced a tractable E. coli K-12 in mice Germ-free or with polymicrobial communities. Whole Genome Sequencing identified potential adaptive targets. Here, we established phenotypic assays as well characterising effects of key mutations and metabolomics was performed with 1H-NMR of intestinal contents. Genes for sugar alcohol metabolism (gat) was the only target common to both mouse models, evidencing specificity. Facing complex microbiota E. coli targeted use of sugar alcohols (srlR, kdgR) and anaerobic respiration (dcuB, focA) [1] whereas alone, we observed instead mutations pointing to increased ability for amino acid use (lrp, dtpB, alaA). Mutations selected correlated dinamically with metabolomics: our results fit the model whereby other microbiota members scavenge oxygen and breakdown complex sugars, limiting E. coli to anaerobically respire simple by-product carbon sources. In the opposing scenario (functional absence) improved amino acid use are favoured colonisation factors. Through experimental evolution we gained insight on shaping E. coli’s metabolic traits through genetic engineering to colonise specific host environments. This work also highlights the versatility of E. coli as potential biotic sensor. [1] Barroso-Batista, J. et al. The first steps of adaptation of Escherichia coli to the gut are dominated by soft sweeps, 2014.

Transcriptomic responses to biotic stresses in Malus x domestica: a meta-analysis study

RNA-Seq analysis is a strong tool to gain insight into the molecular responses to biotic stresses in plants. The objective of this work is to identify specific and common molecular responses between different transcriptomic data related to fungi, virus and bacteria attacks in Malus x domestica. We analyzed seven transcriptomic datasets in Malus x domestica divided in responses to fungal pathogens, virus (Apple Stem Grooving Virus) and bacteria (Erwinia amylovora). Data were dissected using an integrated approach of pathway- and gene- set enrichment analysis, Mapman visualization tool, gene ontology analysis and inferred protein-protein interaction network. Our meta-analysis revealed that the bacterial infection enhanced specifically genes involved in sugar alcohol metabolism. Brassinosteroids were upregulated by fungal pathogens while ethylene was highly affected by Erwinia amylovora. Gibberellins and jasmonates were strongly repressed by fungal and viral infections. The protein-protein interaction network highlighted the role of WRKYs in responses to the studied pathogens. In summary, our meta-analysis provides a better understanding of the Malus X domestica transcriptome responses to different biotic stress conditions; we anticipate that these insights will assist in the development of genetic resistance and acute therapeutic strategies. This work would be an example for next meta-analysis works aiming at identifying specific common molecular features linked with biotic stress responses in other specialty crops.

MetaModules identifies key functional subnetworks in microbiome-related disease.

The human microbiome plays a key role in health and disease. Thanks to comparative metatranscriptomics, the cellular functions that are deregulated by the microbiome in disease can now be computationally explored. Unlike gene-centric approaches, pathway-based methods provide a systemic view of such functions; however, they typically consider each pathway in isolation and in its entirety. They can therefore overlook the key differences that (i) span multiple pathways, (ii) contain bidirectionally deregulated components, (iii) are confined to a pathway region. To capture these properties, computational methods that reach beyond the scope of predefined pathways are needed. By integrating an existing module discovery algorithm into comparative metatranscriptomic analysis, we developed metaModules, a novel computational framework for automated identification of the key functional differences between health- and disease-associated communities. Using this framework, we recovered significantly deregulated subnetworks that were indeed recognized to be involved in two well-studied, microbiome-mediated oral diseases, such as butanoate production in periodontal disease and metabolism of sugar alcohols in dental caries. More importantly, our results indicate that our method can be used for hypothesis generation based on automated discovery of novel, disease-related functional subnetworks, which would otherwise require extensive and laborious manual assessment. metaModules is available at https://bitbucket.org/alimay/metamodules/ a.may@vu.nl or s.abeln@vu.nl Supplementary data are available at Bioinformatics online.

Sorbitol dehydrogenase is a cytosolic protein required for sorbitol metabolism in Arabidopsis thaliana

Sorbitol is converted to fructose in Rosaceae species by SORBITOL DEHYDROGENASE (SDH, EC 1.1.1.14), especially in sink organs. SDH has also been found in non-Rosaceae species and here we show that the protein encoded by At5g51970 in Arabidopsis thaliana (L.) Heynh. possesses the molecular characteristics of an SDH. Using a green fluorescent protein-tagged version and anti-SDH antisera, we determined that SDH is cytosolically localized, consistent with bioinformatic predictions. We also show that SDH is widely expressed, and that SDH protein accumulates in both source and sink organs. In the presence of NAD+, recombinant SDH exhibited greatest oxidative activity with sorbitol, ribitol and xylitol as substrates; other sugar alcohols were oxidized to a lesser extent. Under standard growth conditions, three independent sdh- mutants developed as wild-type. Nevertheless, all three exhibited reduced dry weight and primary root length compared to wild-type when grown in the presence of sorbitol. Additionally, under short-day conditions, the mutants were more resistant to dehydration stress, as shown by a reduced loss of leaf water content when watering was withheld, and a greater survival rate on re-watering. This evidence suggests that limitations in the metabolism of sugar alcohols alter the growth of Arabidopsis and its response to drought.

(23) Sorbitol Transport, Sorbitol, and Watercore in Apple Cultivars Differ in Watercore Susceptibility

Sorbitol is the major carbohydrate translocated into apple fruit where it is normally metabolized to fructose. In watercored apple fruit tissues, however, the intercellular spaces become flooded and sorbitol content is consistently higher than in nonwatercored apples, suggesting a defect in sugar alcohol metabolism or transport. Our previous results have identified and characterized two sorbitol transporters, MsSOT1 and MsSOT2, in apple fruit tissues. Sorbitol transporter gene expression has been implicated in development of watercore with MsSOT expression diminished or absent in certain watercored fruit tissues. To explore this further, we have investigated the relationships between watercore, fruit maturation, fruit composition, and MsSOT expression in a number of apple cultivars that differ in watercore susceptibility. We also compared transporter expression between affected (watercored) and healthy parts of the same fruit and between watercored and nonwatercored fruits throughout the maturation and ripening processes. The MsSOT expression was often dramatically reduced in fruit tissues exhibiting watercore. Thus, in susceptible cultivars, maturing (ripening) fruit parenchyma cells lose the ability to transport sorbitol, and this in turn leads to sorbitol accumulation in the apoplastic free space and subsequent flooding of these spaces. These results are consistent with a relationship between watercore and sorbitol transport and also with a genetic susceptibility to the disorder.

Analysis of celery (Apium graveolens) mannitol dehydrogenase (Mtd) promoter regulation in Arabidopsis suggests roles for MTD in key environmental and metabolic responses.

Of the growing list of promising genes for plant improvement, some of the most versatile appear to be those involved in sugar alcohol metabolism. Mannitol, one of the best characterized sugar alcohols, is a significant photosynthetic product in many higher plants. The roles of mannitol as both a metabolite and an osmoprotectant in celery (Apium graveolens) are well documented. However, there is growing evidence that 'metabolites' can also have key roles in other environmental and developmental responses in plants. For instance, in addition to its other properties, mannitol is an antioxidant and may have significant roles in plant-pathogen interactions. The mannitol catabolic enzyme mannitol dehydrogenase (MTD) is a prime modulator of mannitol accumulation in plants. Because the complex regulation of MTD is central to the balanced integration of mannitol metabolism in celery, its study is crucial in clarifying the physiological role(s) of mannitol metabolism in environmental and metabolic responses. In this study we used transformed Arabidopsis to analyze the multiple environmental and metabolic responses of the Mtd promoter. Our data show that all previously described changes in Mtd RNA accumulation in celery cells mirrored changes in Mtd transcription in Arabidopsis. These include up-regulation by salicylic acid, hexokinase-mediated sugar down-regulation, and down-regulation by salt, osmotic stress and ABA. In contrast, the massive up-regulation of Mtd expression in the vascular tissues of salt-stressed Arabidopsis roots suggests a possible role for MTD in mannitol translocation and unloading and its interrelation with sugar metabolism.

Molecular cloning of mannose-6-phosphate reductase and its developmental expression in celery.

Compared with other primary photosynthetic products (e.g. sucrose and starch), little is known about sugar alcohol metabolism, its regulation, and the manner in which it is integrated with other pathways. Mannose-6-phosphate reductase (M6PR) is a key enzyme that is involved in mannitol biosynthesis in celery (Apium graveolens L.). The M6PR gene was cloned from a leaf cDNA library, and clonal authenticity was established by assays of M6PR activity, western blots, and comparisons of the deduced amino acid sequence with a celery M6PR tryptic digestion product. Recombinant M6PR, purified from Escherichia coli, had specific activity, molecular mass, and kinetic characteristics indistinguishable from those of authentic celery M6PR. Sequence analyses showed M6PR to be a member of the aldo-keto reductase superfamily, which includes both animal and plant enzymes. The greatest sequence similarity was with aldose-6-phosphate reductase (EC 1.1.1.200), a key enzyme in sorbitol synthesis in Rosaceae. Developmental studies showed M6PR to be limited to green tissues and to be under tight transcriptional regulation during leaf initiation, expansion, and maturation. These data confirmed a close relationship between the development of photosynthetic capacity, mannitol synthesis, and M6PR activity.

Physiology and metabolism of sugar alcohols in higher plants

Until recently sugar alcohols received little or no mention in plant physiology texts. The omission is surprising for several reasons. Sugar alcohols are common constituents of many organisms. In fungi, algae and lichens they are frequently the major single carbohydrate present (Bieleski 1982, Lewis 1984). In these organisms, as well as in certain angiosperms, they play a central role in metabolism and physiology, often functioning as the common currency of carbohydrate metabolism in place of neutral sugars like sucrose and polysaccharides like starch. Sugar alcohols are acyclic polyols. The term acyclic polyol refers to a straight-chain, polyhydric alcohol, and, along with alditol, sugar alcohol, polyalcohol and polyhydric alcohol is commonly used in reference to the reduction products of sugars and closely related derivatives. In these compounds the aldehyde or keto group of a sugar is reduced to a hydroxyl group. Most acyclic polyols have both trivial and systematic chemical names, being named for their original source and the sugar from which they are derived, e.g., sorbitol (from Sorbus) is also named glucitol (from glucose), and adonitol (from Adonis) is also ribitol (from ribose). Nomenclature can, however, be complicated and more detailed discussions are available (Bieleski 1982). Chemically, physically and biologically the sugar alcohols (hereafter polyols) closely resemble the sugars from which they are derived and it is usually convenient to regard them as special kinds of sugars or carbohydrates. Unfortunately, many techniques used by physiologists for carbohydrate analyses do not reveal the presence of polyols. Gas and high pressure liquid chromatography can, however, be used to separate and identify all the polyols, and enzymic analysis is available for sorbitol.

The effect of dietary xylitol on the ability of rat caecal flora to metabolise xylitol.

The effect of dietary xylitol on the ability of the rat caecal flora to metabolise xylitol was investigated. Xylitol metabolism in micro-organisms has generally been assessed in terms of pH change and acid production which are often insensitive in demonstrating low rates of substrate utilisation. Using a rapid and sensitive radioisotopic assay, in which 14CO2 production from [U-14C] xylitol was measured, it was possible to show that the caecal microflora obtained from rats can metabolise xylitol. This activity was increased 10, 15, 30 and 40-fold in the caecal flora taken from rats fed diets containing 2.5,5,10 and 20% xylitol, respectively. Using the caecal microflora of normally fed rats, the order of 14CO2 production from 14C-labelled sugars and sugar alcohols was glucose greater than fructose greater than xylose greater than sorbitol greater than or equal to xylitol. The feeding of glucose and fructose did not alter the 14CO2 producing activities, whereas xylose feeding increased xylose metabolism, sorbitol feeding increased sorbitol and xylitol metabolism, xylitol feeding increased sorbitol, xylose and its own metabolism and arabitol feeding increased xylose and sorbitol metabolism. Marked changes were also observed in the population of the caecal flora of xylitol-fed rats, with increases in the number of gram-positive bacteria, compared to rats on a normal diet. Possible mechanisms for these effects involve mutation, selection of micro-organisms capable of metabolising sugar alcohols, and the induction of enzymes involved in sugar alcohol metabolism.

LICHEN METABOLISM. 1. THE USE OF TRITIUM LABELLED WATER IN STUDIES OF ANHYDROBIOTIC METABOLISM IN RAMALINA CELASTRI AND PELTIGERA POLYDACTYLA

SummaryA new radiochemical technique has been applied to a study of anhydrobiotic metabolism in the lichen species, Ramalina celastri (Sprengel) Krog & Swinsc. and Peltigera polydactyla (Neck.) Hoffm. Specimens were incubated in known atmospheric humidities of THO vapour which were found to equilibrate with cellular H2O within 5 days. This method has proved effective in a study of a wide range of in vivo metabolic processes occurring at both high and low cellular water contents.Qualitative and quantitative estimations of the 3H labelling of water soluble cell constituents (ammo acids, organic acids, sugars, sugar phosphates, and sugar alcohols), neutral and polar lipids, water soluble macromolecules, and insoluble cell residues have shown that diverse metabolic systems have significantly different levels of resistance to desiccation. Tricarboxylic acid cycle reactions and related amino acid interconversions were shown to be relatively desiccation resistant, whereas Calvin cycle metabolism appeared to be highly sensitive, a conclusion supported by 14CO8 tracer experiments. Conversely, the synthesis of sugar alcohols was found to be active beyond the limit of photosynthetic metabolism. Neither lipid nor macromolecular synthesis was shown to occur to a significant degree in either lichen in the desiccated state.It is proposed that the syntheses of amino acids and sugar alcohols at low cellular saturation levels are important physiological processes. Amino acid synthesis results in the accumulation of an available store of stable intermediates, ready to feed into the T.C.A. cycle by trans‐amination or deamination on rehydration of the lichen. Sugar alcohol metabolism assists in the maintenance of a high sugar alcohol concentration to act as a physiological buffer during extreme dehydration.