L-malic Acid Research Articles

Functional biopolyesters based on cross-linked Poly(L-malic acid): Network engineering towards tailoring brittle-ductile transition and shape-memory performance

Crosslinking opens more possibilities of biodegradable poly (L-malic acid) (PLMA) as functional materials, and network structure is key to its mechanical states and final applications. In this work, the diols with various chain lengths, including six types of fatty diols and four types of polyethylene glycols, were used to construct networks in PLMA, aiming at establishing network structure-mechanical state-material function correlations. As the molecular weights of diols increased from 100 to 400, the samples experienced evident transition from high-strength plastic to low-loss rubber, finally to soft elastomer. The strengths and Young's moduli varied from 71 MPa to 0.6 MPa and from 2.3 GPa to 2.7 MPa, respectively, accompanied by a broad variation of glass transition temperature (Tg, 50 oC–7 oC). This brittle-ductile transition was revealed in terms of elastoplastic and dielectric relaxations, then. Using the samples with different network structures as components, the actuators with attractive capability to complete asynchronous actions were fabricated. This work proposes promising applications of cross-linked PLMA as functional or smart materials due to its easily-tuned mechanical states and Tg, together with its good antibactierial activity and shape memory effect.

Molecular characteristics and digestion properties of corn starch esterified by l ‐malic acid

Malate starch was prepared by dry heat treatment of corn starch with l-malic acid. Malate starch has lower swelling degree and gelatinization property than the original starch. The polarization cross gradually disappears, and the particle size becomes larger. However, as the degree of substitution increased, the polarization cross became weak and eventually disappeared due to the destruction of the crystal structure. The results of infrared spectroscopy indicated that malate starch showed a characteristic peak of carbonyl vibration at 1,739 cm−1, and the peak value of the substitution increased significantly. The weak peak in the 165–180 region of the nuclear magnetic carbon spectrum is the chemical shift of the ester carbonyl carbon formed by esterification. The 13C NMR results speculated that the hydroxyl group of l-malic acid C9 and starch C6 was esterified to form malate starch. The digestion experiments showed that the content of resistant starch after esterification increased significantly. Practical applications Esterified starch is an important part of modified starch. After organic acid treatment, starch can be more widely used in various industries according to its different properties. In this study, the low degree of substitution malate starches were constructed by combining the chemical bonds of corn starch and l-malic acid, and the effects on physical and chemical properties, molecular characteristics, and digestion characteristics were studied to improve the processing characteristics of starch and improve the product addition value.

Acetate as substrate for l-malic acid production with Aspergillus oryzae DSM 1863

BackgroundMicrobial malic acid production is currently not able to compete economically with well-established chemical processes using fossil resources. The utilization of inexpensive biomass-based substrates containing acetate could decrease production costs and promote the development of microbial processes. Acetate is a by-product in lignocellulosic hydrolysates and fast pyrolysis products or can be synthesized by acetogens during syngas fermentation. For the fermentation of these substrates, a robust microorganism with a high tolerance for biomass-derived inhibitors is required. Aspergillus oryzae is a suitable candidate due to its high tolerance and broad substrate spectrum. To pave the path towards microbial malic acid production, the potential of acetate as a carbon source for A. oryzae is evaluated in this study.ResultsA broad acetate concentration range was tested both for growth and malic acid production with A. oryzae. Dry biomass concentration was highest for acetic acid concentrations of 40–55 g/L reaching values of about 1.1 g/L within 48 h. Morphological changes were observed depending on the acetate concentration, yielding a pellet-like morphology with low and a filamentous structure with high substrate concentrations. For malic acid production, 45 g/L acetic acid was ideal, resulting in a product concentration of 8.44 ± 0.42 g/L after 192 h. The addition of 5–15 g/L glucose to acetate medium proved beneficial by lowering the time point of maximum productivity and increasing malic acid yield. The side product spectrum of cultures with acetate, glucose, and cultures containing both substrates was compared, showing differences especially in the amount of oxalic, succinic, and citric acid produced. Furthermore, the presence of CaCO3, a pH regulator used for malate production with glucose, was found to be crucial also for malic acid production with acetate.ConclusionsThis study evaluates relevant aspects of malic acid production with A. oryzae using acetate as carbon source and demonstrates that it is a suitable substrate for biomass formation and acid synthesis. The insights provided here will be useful to further microbial malic acid production using renewable substrates.

RETRACTED ARTICLE: Structural Diversity of Co(II) Coordination Polymers: Treatment Activity on Hypotension During Surgery by Blocking α Receptor on Peripheral Blood Vessels

Two Co(II)-based coordination polymers (CPs) with the molecular formulae of [Co4(5-mtz)4(l-mal)2(H2O)2]n (1, 5-mtz = 5-methyltetrazole, L-mal = L-malic acid) and {[Co8(S-mal)4(bptc)(H2O)12]·0.5H4bptc·7.5H2O}n (2, S-mal = S-malic acid, H4bptc = biphenyl-3,3′,5,5′-tetracarboxylic acid) were synthesized under a hydrothermal or solvothermal surrounding. The prepared two complexes have been determined through the powder and single crystal X-ray diffraction, thermogravimetric (TG) analyses and IR spectroscopy. To prevent the hypotension during surgery after injected with anesthetic, their biological activity was estimated in this research. The CCK-8 (Cell Counting Kit-8) assay was performed to measure the viability of the HUVEC cells after compounds treatment. The relative expression of the α receptor was evaluated by real time RT-PCR (reverse transcription-polymerase chain reaction). Besides, the blood pressure was measured as well.

Impact of esterification with malic acid on the structural characteristics and in vitro digestibilities of different starches

This research focused on the structural characteristics of resistant starches (RSs) that were obtained from corn, potato, and sweet potato and esterified by L-malic acid. Further, the unique effect of the degree of substitution (DS) on the crystalline properties was studied. Different starches were allowed to react with 2 M malic acid (pH 1.5) for 12 h at 130 °C. The shapes of the granules and the Maltese-cross shapes of samples were maintained and visible under an optical microscope. The FT-IR spectrum displayed evident carbonyl peaks at 1740 cm−1, and the onset temperature (To) and gelatinization enthalpy (∆H) gradually decreased as DS increased. The malic acid-treated starches exhibited an increased RS content compared to those of the control. The RS contents of potato, sweet potato, and corn, which were 65.5%, 70.0%, and 89.8% in the uncooked MT-samples, decreased to 57.3%, 63.8%, and 86.7% in the cooked MT-samples, respectively, and exhibited high heat stability; corn starch yielded the highest RS among them. The thermal and malic acid treatments resulted in the partial hydrolysis and rearrangement of the helix structure of crystalline area, which was affected by esterification. The result revealed that the RS content increased as that of DS escalated.

Effect of alcoholic and acetous fermentations on the phenolic acids of Kei-apple (Dovyalis caffra L.) fruit.

The Kei apple is a tree found on the African continent. Limited information exists on the effect of alcoholic and acetous fermentation on the phytochemicals of Kei apple. The fruit has increased concentrations of l-malic, ascorbic, and phenolic acids among other compounds. Juice was co-inoculated with Schizosaccharomyces pombe (Sp) and Saccharomyces cerevisiae (Sc) to induce alcoholic fermentation (AF). Acetous fermentation followed AF, using an acetic acid bacteria (AAB) consortium. Saccharomyces cerevisiae + Sp wines and vinegars had the highest pH. Total acidity, soluble solids and l-malic acid decreased during AF and acetous fermentation, and was highest in Sc wines and vinegars. Volatile acidity (VA) concentration was highest in Sp vinegars but was not significantly different from Sc and Sc + Sp vinegars. Gallic acid was highest in Sp wines and vinegars, whereas syringic acid was highest in Sc wines and vinegars. The Sc + Sp wines were highest in caffeic, p-coumaric, and protocatechuic acids. Schizosaccharomyces pombe vinegars were highest in caffeic and p-coumaric acids. Highest concentrations of ferulic and sinapic acids were found in Sp and Sc wines, respectively. Chlorogenic acid was most abundant phenolic acid in both wines and vinegars. Saccharomyces cerevisiae + Sp and Sc fermentation had a positive effect on most phenolic acids; Sc + AAB had an increased effect on syringic and chlorogenic acids, whereas Sp + AAB resulted in an increase in gallic, caffeic, and p-coumaric acids. The AAB selected had minimal performance with respect to VA production in comparison to commercial vinegars. Acetic acid bacteria selection for acetous fermentation should therefore be reconsidered and the decrease of certain phenolic acids during acetous fermentation needs to be investigated. © 2021 Society of Chemical Industry.

The Effect of Exogenous Free Nε-(Carboxymethyl)Lysine on Diabetic-Model Goto-Kakizaki Rats: Metabolomics Analysis in Serum and Urine.

The current study investigated the effects of exogenous free Nε-(carboxymethyl) lysine (CML) from daily diet on diabetic-model Goto-Kakizaki rats. Rats were fed with free CML (2 mg/kg body weight) for 8 weeks, then metabolomics evaluation was performed on serum and urine, and biochemical and histopathologic examinations were conducted to verify metabolic results. Diabetic rats fed with free CML showed significantly increased (P < 0.05) fasting blood glucose (11.1 ± 1.07 mmol/L) and homeostasis model assessment values (homeostatic model assessment of insulin resistance: 16.0 ± 4.24; homeostatic model assessment of beta cell function: 6.66 ± 2.01; and modified beta cell function index: 11.5 ± 2.66) and a significantly altered (P < 0.05) oxidative stress level when compared to the control group. Serum and urine metabolomics showed a significantly altered (P < 0.05) level of aminomalonic acid, 2-oxoadipic acid, l-malic acid, β-alanine, 2-oxoglutaric acid, d-threitol, N-acetyl-leucine, methylmalonic acid, l-cysteine, thymine, glycine, l-alanine, 4-hydroxyproline, hexadecane, succinic acid, l-ornithine, gluconolactone, maleic acid, l-lactate, tryptophan, 5-methoxyindoleacetate, γ-aminobutyric acid, homoserine, maltose, and quinolinic acid. Our results indicated that these metabolites altered by exposure to exogenous free CML were mapped to the citric acid cycle and amino acid and carbohydrate metabolism, which might be related to increased progression of diabetes and some other diabetic complications, including diabetic brain and neurological diseases, retinopathy, nephropathy, and impaired wound healing.

Fermentation process optimization and chemical composition analysis on black tea wine

In this study, the fermentation process of black tea wine was optimized, and the changes in catechins, organic acids, and aroma components during fermentation were investigated. The optimal fermentation conditions for tea wine were determined as follows: the addition of 15% sucrose and 0.75% tea leaves, and a fermentation temperature of 25 ºC. Under the optimal conditions, the alcohol content and sensory evaluation score of tea wine were 8.9 %ABV and 88, respectively. The contents of catechins and organic acids in tea wine were 21.29 mg/L and 3.68 mg/mL, which were 1.32-fold and 10.51-fold higher than those of tea infusion, respectively. L-malic acid was the main organic acid in tea wine, which accounted for 56.3% of the total amount of organic acids. A total number of 34 and 33 kinds of aroma components were detected in tea wine and tea infusion, respectively. The main aroma components of tea wine were esters and alcohols, which accounted for 39.7% and 45.9% of the total amount of aroma components, respectively, while the main aroma components of tea infusion were esters and aldehydes, accounting for 34.6% and 33.2%, respectively.

Prevention of a hydrogen explosion accident in the wet aluminum waste dust collection process based on L-malic acid

To essentially solve the hydrogen explosion risk in wet aluminum waste dust collection systems employed in aluminum product processing, nontoxic and environmentally friendly L-malic acid was used to inhibit the hydrogen production reaction between aluminum waste dust and water. Experiments and chemical kinetic model analysis showed that when the L-malic acid concentration reached 0.15 g L−1, the hydrogen production reaction was almost completely suppressed. Scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and adsorption theory were used to analyze the hydrogen suppression mechanism. The results showed that L-malic acid forms a chemical adsorption film on the surface of aluminum waste dust particles that can prevent particles from contacting water and realizes hydrogen suppression by preventing the reaction from proceeding. This method provides a design safety measure to prevent hydrogen explosion in wet aluminum waste dust collection systems and has good application prospects.

Study on the solid-liquid equilibrium of l-malic acid in binary solvents

In this study, the solubility of l-malic acid in three binary solvents (ethyl acetate + tetrahydrofuran, acetonitrile + tetrahydrofuran, butyl acetate + acetonitrile) at atmospheric pressure from T = (278.15 to 323.15) K was measured via a gravimetric method. The results show that in the temperature range studied, the solubility of l-malic acid in the selected solvent gradually increases with the increase of temperature. The solubility of l-malic acid increases with the increase of the mass fraction of tetrahydrofuran at the binary system (ethyl acetate + tetrahydrofuran, acetonitrile + tetrahydrofuran), the solubility of l-malic acid increases with The mass fraction of butyl acetate increases and decreases at the butyl acetate + acetonitrile system. In addition, the dissolution behavior of l-malic acid was explained using Hansen solubility parameter (HSP). Furthermore, the solubility data were correlated with using the modified Apelblat equation, the NRTL model and the newly proposed Apelblat-Sun model, the results have shown that the modified Apelblat equation has the best fitting effect. After research found, the hydrogen bonding force plays a key role in the solubility of l-malic acid. So solubility of l- resulted malic acid from the integrated effect of solute–solvent and solvent–solvent interactions. In addition, the van't Hoff equation was used to calculate and discuss all thermodynamic parameters of dissolution, Including standard Gibbs dissolution (ΔsolGo), standard dissolution enthalpy (ΔsolHo) and standard dissolution entropy (ΔsolSo), Where ΔsolHo，ΔsolSo，ΔsolGo were all greater than 0, it have been shown that the dissolution process is driven by heat absorption and entropy. This study can provide basic thermodynamic data for the crystallization and industrial separation of l-malic acid.

Characterization of fatty acids, amino acids and organic acids in three colored quinoas based on untargeted and targeted metabolomics

In this study, fatty acids, amino acids and organic acids in three color quinoas (WQ, white quinoa; RQ, red quinoa; BQ, black quinoa) were analyzed based on untargeted and targeted metabolomics. A total of 20 fatty acids, 30 amino acids and 17 organic acids were detected, and 4 fatty acids, 12 amino acids, and 12 organic acids were reported in quinoas for the first time. Significant differences (p < 0.05) of fatty acids (256.65 mg/g in RQ to 294.10 mg/g in BQ), amino acids (6627.54 μg/g in WQ to 10452.72 μg/g in BQ) and organic acids (21.21 mg/g in WQ to 31.84 mg/g in RQ) were presented in different quinoas. C16:0 (77.26 mg/g～97.58 mg/g), C18:2n6c (73.26 mg/g～99.67 mg/g), glutamic acid (1926.43 μg/g～3632.53 μg/g), tyrosine (931.00 μg/g～1197.94 μg/g), succinic acid (12.16 mg/g～17.30 mg/g) and l-malic acid (1.14 mg/g～5.39 mg/g) were common in quinoas. According to principal component analysis (PCA), WQ could be characterized by heptadecanoic acid (1.99 mg/g), palmitic acid (97.58 mg/g), glutamine (5.43 μg/g), ornithine (53.78 μg/g) and citric acid (0.79 mg/g); BQ was characterized by oleic acid (86.33 mg/g), myristic acid (2.02 mg/g), beta-alanine (31.64 μg/g), tyrosine (1197.94 μg/g), proline (2003.69 μg/g) and lactic acid (2.57 mg/g); RQ was characterized by l-alanine (746.41 μg/g), l-norvaline (6.67 μg/g), succinic acid (17.30 mg/g) and l-malic acid (5.39 mg/g), respectively. In conclusion, characterization of fatty acids, amino acids and organic acids in three colored quinoas could be well analyzed based on metabolomics.

Effects of corn steep liquor on \u03b2-poly(l-malic acid) production in Aureobasidium melanogenum

β-poly(l-malic acid) (PMLA) is a water-soluble biopolymer used in medicine, food, and other industries. However, the low level of PMLA biosynthesis in microorganisms limits its further application in the biotechnological industry. In this study, corn steep liquor (CSL), which processes high nutritional value and low-cost characteristics, was selected as a growth factor to increase the PMLA production in strain, Aureobasidium melanogenum, and its metabolomics change under the CSL addition was investigated. The results indicated that, with 3 g/L CSL, PMLA production, cell growth, and yield (Yp/x) were increased by 32.76%, 41.82%, and 47.43%, respectively. The intracellular metabolites of A. melanogenum, such as amino acids, organic acids, and key intermediates in the TCA cycle, increased after the addition of CSL, and the enrichment analysis showed that tyrosine may play a major role in the PMLA biosynthesis. The results presented in this study demonstrated that the addition of CSL would be an efficient approach to improve PMLA production.

Chiral single-walled carbon nanotubes as chiral selectors in multimode enantioselective sensors.

Single-walled carbon nanotube-(7,6) chirality was used for the design of multimode enantioselective sensors using different carbon matrices such as graphene paste, graphite paste, and carbon nanopowder-based paste. l- and d-malic acids were used as model analytes. The responses of the multimode sensors were evaluated for potentiometric and differential pulse voltammetry (DPV) modes. When carbon nanopowder was used as matrix, the multimode sensor was enantioselective for d-malic acid in the concentration range 10-3 to 10-15 mol/L for the potentiometric mode and 10-5 to 10-8 mol/L for the DPV mode. The graphite paste-based sensor was enantioselective for l-malic acid in the ranges: 10-10 to 10-13 for the potentiometric mode and 10-4 to 10-7 mol/L for the DPV mode. The sensors based on graphene and chiral single-walled carbon nanotubes were enantioselective for d-malic acid, and a response was obtained only in the DPV mode. Accordingly, the matrix influenced both the enantioselectivity and the sensitivity of the measurements. The application of the sensors was for the enantioanalysis of malic acid in wines and apple juice samples. The proposed method is fast and reliable and allows the quantification of l- and d-malic acids using electrochemical methods based on different principles, from the real samples after a buffering of the samples. The enantioanalysis of malic acid in wine and juice samples was performed with high recoveries (higher than 90.00%) and low relative standard deviation (RSD) (%) values (lower than 1.00%).

Chemical composition and sensory properties of fermented citrus juice using probiotic lactic acid bacteria

We prepared three types of fermented citrus juice using probiotic lactic acid bacteria (Lactobacillus plantarum SI-1 and L. pentosus MU-1). The viable cell counts, chemical composition, and sensory properties of citrus juice were investigated and compared before and after fermentation. Similar to probiotic foods, fermented citrus juice contains sufficient viable cell counts. Decreased concentrations of l-malic acid and specific free amino acids and increased concentration of lactic acid were observed in fermented citrus juice. However, the total sugar concentration remained unchanged. Therefore, L. plantarum SI-1 and L. pentosus MU-1 grow in citrus juice via malolactic fermentation. Furthermore, no difference was observed in the sensory properties of citrus juice following lactic acid fermentation. These findings demonstrate the growth mechanism of lactic acid bacteria in citrus juice and sensory properties of fermented citrus juices.

Analysis of Organic Acids and Antioxidant Activity in Vitro of Citrus medica Jiaosu during Fermentation Process

Changes in the composition of organic acids and in vitro antioxidant activity of Citrus medica Jiaosu were investigated. During fermentation,scavenging rate on superoxide radical,hydroxyl radical and ABTS radical showed an increasing trend generally. DPPH radical scavenging rate and reducing power initially increased,then decreased,and gradually increased afterwards. The main organic acids of Citrus medica Jiaosu were L-malic acid and citric acid during 5~15 d fermentation,while they were lactic acid,acetic acid and L-tartaric acid during 40~90 d. Meanwhile,shikimic acid,ascorbic acid,succinic acid and oxalic acid were found in Citrus medica Jiaosu. The amount of total organic acid increased firstly,then decreased and then increased again until reaching its peak of(9.600±0.18) mg/mL at 90 d,growing by 105.47% compared with the amount in Citrus medica Jiaosu at 5 d. The different time points and species of organic acids were classified into two and three groups respectively by cluster analysis when rescaled distance cluster was 15. Both superoxide radical and hydroxyl radical scavenging rate showed extremly(P<0.01)significant positive correlation with the contents of lactic acid(the spatial correlation coefficient was 0.885 and 0.680 respectively). The research results revealed the changes in the composition of organic acids and in vitro antioxidant activity of Citrus medica Jiaosu,and provided a theoretical reference for precision preparation of Citrus medica Jiaosu.

Compact analytical flow system for the simultaneous determination of l-lactic and l-malic in red wines

During the malolactic fermentation of red wines, l-malic acid is mainly converted to l-lactic acid. Both acids should be precisely measured during the entire process to guarantee the quality of the final wine, thus making real-time monitoring approaches of great importance in the winemaking industry. Traditional analytical methods based on laboratory procedures are currently applied and cannot be deployed on-site. In this work, we report on the design and development of a bi-parametric compact analytical flow system integrating two electrochemical biosensors that could be potentially applied in this scenario. The developed flow-system will allow for the first time the simultaneous measurement of both acids in real scenarios at the real-time and in remote way. Miniaturized thin-film platinum four-electrode chips are fabricated on silicon substrates by standard photolithographic techniques and further implemented in a polymeric fluidic structure. This includes a 15 µL flow cell together with the required fluidic channels for sample and reagent fluid management. The four-electrode chip includes counter and pseudo-reference electrodes together with two working electrodes. These are sequentially modified with electropolymerized polypyrrole membranes that entrap the specific receptors for selectively detecting both target analytes. The analytical performance of both biosensors is studied by chronoamperometry, showing a linear range from 5 × 10−6 to 1 × 10−4 M (LOD of 3.2 ± 0.3 × 10−6 M) and from 1 × 10−7 to 1 × 10−6 M (LOD of 6.7 ± 0.2 × 10−8 M) for the l-lactate and the l-malate, respectively. Both biosensors show long-term stability, retaining more than the 90% of their initial sensitivity after more than 30 days, this being a prerequisite for monitoring the whole process of the malolactic fermentation of the red wines (time between 20 and 40 days). The flow system performance is assessed with several wine samples collected during the malolactic fermentation process of three red wines, showing an excellent agreement with the results obtained with the standard method.

Colour Evaluation of Pinot Noir and Merlot Wines after Malolactic Fermentation Carried out by Oenococcus oeni and Lactobacillus plantarum Patagonian Native Strains

Malolactic fermentation is a complex process that involves many reactions aside from the decarboxylation of L-malic acid. But we still have only glimpses of that complexity. It is not clear if the phenolic composition and colour are affected by malolactic fermentation and, if so, to what extent. So, the aims of this study were: 1) to evaluate the behaviour of native Patagonian strains of Oenococcus oeni and Lactobacillus plantarum in two wine varieties, and 2) to analyse the effect of malolactic fermentation on the colour of these wines. Our results show that the survival of bacteria and L-malic acid decarboxylation is different depending on the lactic acid bacteria strain employed and the wine variety. In addition, we found that O. oeni can survive in wine even when L-malic acid is not being consumed. We found some correlations between MLF and colour-related parameters in Pinot noir but not for Merlot. In fact, some of the colour-related parameters measured in Merlot (total polyphenolic index, colour intensity, hue, as well as the CIELAB parameters) were affected even when L-malic acid was not being consumed.

Characterization and Optimization of L-Malic Acid Production by Some Clinical Isolates of Aureobasidium pullulans

Background: Poly-L-malic acid (PLMA) comprises aliphatic polyester polymers with broad applications in pharmaceutical industries. The fungal microorganisms are among the best natural sources recruited to supply L-malic acid (MA) as a precursor of PLMA. In this study, we investigated MA production ability of 7 clinical isolated of the fungus Aureobasidium pullulans. Materials and Methods: Seven clinical isolates of A. pullulans acquired from Westerdijk Fungal Biodiversity Institute were studied, and the isolate with the highest total MA production was selected for the optimization process. We tried to optimize the output by applying different concentrations of CaCO3 in fungus medium (1.5%, 3%, and 6%) and various incubation temperatures (27°C, 32°C, and 37°C) during 3, 7, and 14 days. Results: Intra-strains variation was significantly strong (P&lt;0.0001), and the highest production of MA was carried out by the isolate A. pullulans var. melanigenum dH 21931, UTHSC 06-456. The amount of MA produced by this strain was significantly higher in medium with 3% CaCO3 compared with other concentrations of CaCO3 and after 7 days incubation than the other fermentation times (P&lt;0.05). Although MA production was higher at 27°C, the differences between the investigated various temperatures were not significant (P&gt;0.05). Conclusion: Overall, we obtained the highest MA production in Sabouraud dextrose agar (SDA)medium with 3% CaCO3 at 27°C after 7 days of incubation. Our study indicated that the fermentation period and CaCO3 concentration significantly alter MA production in A. pullulans var. melanigenum.

Evaluating the effect of using non-Saccharomyces on Oenococcus oeni and wine malolactic fermentation

Interest in using non-Saccharomyces yeasts in winemaking has increased in recent years due to their ability to improve wine quality. However, little information has been published regarding the possible effect on malolactic fermentation (MLF), carried out mostly by Oenococcus oeni. The aim of this paper is therefore to evaluate the effect of the most representative non-Saccharomyces species on O. oeni and wine MLF. Different strains of Torulaspora delbrueckii, Metschnikowia pulcherrima, Hanseniaspora uvarum, Hanseniaspora vineae and Starmerella bacillaris (syn. Candida zemplinina) were used in sequential alcoholic fermentation with Saccharomyces cerevisiae. The resulting wines were inoculated with four O. oeni strains. The action of non-Saccharomyces affected the final wine composition and the later role of O. oeni. Some of its strains could not perform MLF in H. uvarum wine due to high SO2 concentrations. In some cases, MLF was inhibited in wines inoculated with S. bacillaris. All the H. uvarum and H. vineae strains notably increased acetic acid concentrations, thus threatening wine quality. The best conditions for MLF were provided by some T. delbruecckii and M. pulcherrima strains, which showed increased concentrations of mannoproteins – compounds described as MLF activators –, no production of SO2, and low consumption of L-malic acid. In conclusion, non-Saccharomyces yeasts have diverse effects on O. oeni and MLF depending on the species, with T. delbrueckii and M. pulcherrima being those that showed the best compatibility with MLF development.

Urine Metabolomics Analysis in Patients With Normoalbuminuric Diabetic Kidney Disease.

ObjectiveDiabetic kidney disease (DKD) leads to low high albuminuria and gradually progresses to very high albuminuria with kidney insufficiency. However, about 20–40% of DKD is normoalbuminuric DKD (NADKD), which has impaired kidney function but normal urine albumin. This study is to investigate the urine metabolomic profiles of patients with NADKD and albuminuria DKD (ADKD).MethodsIn total, 95 patients were divided into a simple diabetes mellitus group (SDM group), an ADKD group, and a NADKD group. All subjects were analyzed for urine metabolites using non-targeted metabolomics based on ultra-performance liquid chromatography – tandem mass spectrometry.ResultsThe urine metabolomic profiles of the SDM group, NADKD group, and ADKD group were significantly different, and 65 different metabolites were identified among the three groups. Metabolic pathway analysis of these differential metabolites found that the top three significantly changed metabolic pathways were linoleic acid metabolism, citrate cycle, and, arginine and proline metabolism. There are 12 metabolites enriched in these three metabolic pathways. In detail, compared with those in the SDM group, the levels of γ-linolenic acid in the ADKD group were increased significantly, while the levels of succinic acid, cis-aconitic acid, citric acid, L-proline, L-erythro-4-hydroxyglutamate, N-methylhydantoin, N-carbamoylputrescine, spermidine, and 5-aminopentanoic acid were reduced significantly; compared with those in the NADKD group, the levels of linoleic acid, γ-linolenic acid, and L-malic acid in the ADKD group were increased significantly (P < 0.05), while the levels of L-proline, L-erythro-4-hydroxyglutamate, N-carbamoylputrescine, and spermidine were significantly reduced (P < 0.05). However, there were no significant difference between the SDM group and NADKD group (P > 0.05).ConclusionThe urine metabolomic profiles between the NADKD group and the ADKD group are significantly different. Specifically, these two groups have distinct levels of linoleic acid, γ-linolenic acid, L-malic acid, L-proline, L-erythro-4-hydroxyglutamate, N-carbamoylputrescine, and spermidine.