L-malic Acid Research Articles

An underlying mechanism for MleR activating the malolactic enzyme pathway to enhance acid tolerance in Lacticaseibacillus paracasei L9.

Tolerance to acid stress is a crucial property of probiotics against gastric acids. The malolactic enzyme pathway is one of the most important acid resistance systems in lactic acid bacteria. It has been reported that the malolactic enzyme pathway was regulated by the transcriptional regulator, MleR. However, regulatory mechanisms underlying malolactic enzyme pathway to cope with acid stress remain unknown. In this study, the acid tolerance ability of the ΔmleR deletion strain was significantly lower than that of the wild-type strain, and the complementation of the mleR gene into the ΔmleR strain restored the acid tolerance of the ΔmleR strain, indicating that MleR was involved in acid tolerance response of Lacticaseibacillus paracasei L9. Real-time quantitative PCR and transcriptional fusion experiments confirmed MleR-activated transcription of the mleST gene cluster. Furthermore, MleR was confirmed to directly bind to the promoter region of the mleST operon using ChIP assays and EMSAs. The transcription start site G of the mleST operon was located at position -198 relative to the start codon of the mleS gene. The region from -80 to -61 upstream of the transcription start site was determined to be essential for MleR binding. Moreover, L-malic acid acted as an effector for MleR to activate the transcription of the mleST operon in a dose-dependent manner. These results revealed the regulatory mechanism behind MleR-mediated activation of the malolactic enzyme pathway to enhance acid tolerance in Lc. paracasei L9. IMPORTANCE Lacticaseibacillus paracasei is extensively used as probiotics in human health and fermented dairy production. Following consumption, Lc. paracasei is exposed to a variety of physico-chemical stresses, such as low pH in the stomach and bile salts in the intestines. The high acidity of the stomach severely inhibits bacterial metabolism and growth. Therefore, the acid tolerance response is critical for Lc. paracasei to survive. It has been reported that the malolactic enzyme (MLE) pathway plays an important role for LAB to resist acid stress. However, the regulatory mechanism has not yet been investigated. In this study, we determined that the LysR-type regulator MleR positively regulated the MLE pathway to enhance acid tolerance by binding -80 to -61 upstream of the transcription start site of the mleST operon. Further, L-malic acid acts as a co-inducer for MleR transcriptional regulation. Our study provides novel insights into acid tolerance mechanisms in LAB.

Augmentation of Performance, Carcass Trait, Biochemical Profile and Lipid Metabolism Concerning the Use of Organic Acidifier in Broiler Chickens

This study aimed to disclose the effects of a new compound organic acidifier mixing with L-malic acid and L-lactic acid on broiler production. A total of 1000 1-day-old Arbor acres broiler chicks were randomly divided into two treatments of 10 replicates each, with 50 birds per replicate. The feeding trial lasted for 42 days. The treatment group was offered 0.8% of the acidifier based on the control. The growth performance of the broiler chickens was improved by treatment. The broiler chickens in treatment had lower triglyceride but higher high-density lipoprotein content in serum. Superoxide dismutase activity, total antioxidant capacity and the concentrations of immunoglobulin A, complement 3 and lysozyme were increased in the serum of the broiler chickens, while the concentrations of interleukin-2 and tumor necrosis factor-α in the mucosa of jejunum were decreased by treatment. The expressions of AMPK, CD36, FABP1, MTTP and PPARα were increased but expressions of APOB100 and PCSK9 were decreased by treatment. In conclusion, the acidifier was effective at promoting broiler production, which was probably through the improved immunity, antioxidant and hepatic lipid metabolism capacities. The acidifier may be accelerating lipid metabolism in broiler chicken liver through regulating the expression of the genes related to fat metabolism.

Enzyme-Like Activity of Cerium Dioxide Colloidal Solutions Stabilized with L-Malic Acid

For the first time, stable aqueous colloidal solutions of cerium dioxide stabilized with L-malic acid have been obtained at ligand : CeO2 molar ratios of 0.2, 0.5, 1.0, and 2.0. Using dynamic light scattering, it has been shown that CeO2 sols are characterized by a narrow monomodal size distribution of aggregates, and the sols remain to be aggregatively stable in a Tris-HCl buffer solution. According to the chemiluminescence analysis of the enzyme-like activity of cerium dioxide sols with respect to hydrogen peroxide, the surface modification of the cerium dioxide particles with malic acid increases the enzyme-like activity of СеО2 up to 4.5 times.

Luteolin alleviates ulcerative colitis in rats via regulating immune response, oxidative stress, and metabolic profiling.

Ulcerative colitis (UC) is an inflammatory bowel disease and associated with metabolic imbalance. Luteolin (LUT) reportedly exhibits anti-inflammatory activity. However, its regulatory effects on metabolites remain indistinct. Here, the effects of LUT on immune response and oxidative stress in UC were determined. Serum metabolomics profiles of UC rats treated with LUT were obtained utilizing liquid chromatography-mass spectrometry. The results revealed that LUT treatment alleviated colon tissue injury, colon shortening, weight loss, and inflammatory response in UC rats. Additionally, the levels of superoxide dismutase and total antioxidant capacity were elevated, but malondialdehyde content was reduced in serum of UC rats, while these changes were abrogated by LUT. Metabolomics analysis unveiled that l-malic acid, creatinine, l-glutamine, and l-lactic acid levels were remarkably decreased, while dimethyl sulfone, 5-methylcytosine, cysteine-S-sulfate, and jasmonic acid levels were notably increased after LUT treatment. Furthermore, differential metabolites primarily participated in d-glutamine and d-glutamate metabolism, glutathione metabolism, and citrate cycle pathways. In summary, these results demonstrated that LUT improved immune response, alleviated oxidative stress, and altered metabolites in UC rats. This study lays the root for further exploring the mechanism of LUT in the treatment of UC.

L-Malic Acid Facilitates Stem Cell-Driven Intestinal Epithelial Renewal through the Amplification of β-Catenin Signaling by Targeting Frizzled7 in Chicks.

l-Malic acid (l-MA) contributes to energy metabolism and nutrient digestion, which is an alternative to antibiotics for livestock; however, it is not clear whether l-MA can replace antibiotics to promote intestinal development in chicks. To investigate the effects of l-MA on intestinal stem cells (ISCs) driving epithelial renewal, we employed in vivo chick feeding experiments, chick intestinal organoid (IO) models, and in vitro chick intestinal epithelial cell models. The results showed that the feed conversion rate and diarrhea scores were decreased with improved jejunal morphology and barrier function in the 0.5% l-MA group. l-MA promoted the proliferation and differentiation of ISCs, inhibited the cell apoptosis, increased the IO formation efficiency, surface area, budding efficiency, and number of buds, suggesting that l-MA promoted the expansion of ISCs. Furthermore, l-MA treatment dramatically upregulated the Wnt/β-catenin signaling pathway in the jejunum. Importantly, Wnt transmembrane receptor Frizzled7 (FZD7) mRNA abundance was increased in response to dietary 0.5% l-MA. In addition, molecular docking analysis using Autodock software and isothermal titration calorimetry revealed that l-MA binds to Lys91 of FZD7 with high affinity, indicating a spontaneous interaction. The chick intestinal epithelial cells treated with 10 μM l-MA significantly increased cell viability, and the Wnt/β-catenin signaling pathway was activated, but l-MA failed to upregulate the Wnt/β-catenin signaling when treated with the FZD7-specific inhibitor Fz7-21 in chick intestinal epithelial cells, indicating that FZD7 is indispensable for l-MA activation of the Wnt/β-catenin signaling. Collectively, l-MA stimulated β-catenin signaling by targeting transmembrane receptor FZD7, which promoted ISC expansion and inhibited cell apoptosis to accelerate intestinal epithelial renewal in chicks.

Biocatalytic synthesis of new polyesteramides from ε-caprolactam and hydroxy acids: Structural characterization, biodegradability, and suitability as drug nanocarriers

The synthesis of polyesters and polyamides by enzyme-catalyzed processes in vitro was developed in the last decades as a green alternative to obtain biodegradable synthetic polymers with various applications, such as nanoparticle-sized carriers for drug delivery. Polyesteramides were much less studied in this respect, although having the presumable advantage of increased mechanical and thermic resistance brought by the amide moieties. In this work, polyesteramides were synthesized for the first time employing as raw materials ε-caprolactam and a hydroxy acid. L-malic, 3-hydroxybutyric, 12-hydroxystearic and 16-hydroxyhexadecanoic acid, respectively, were investigated as co-monomers in solventless or organic medium, using the immobilized lipase Novozyme 435 as catalyst. The short chain hydroxy acids holding secondary hydroxyl groups yielded oligomers with average degree of polymerization no higher than 4, while in the case of the long-chain 12-hydroxystearic acid this value increased to 7. The best results were achieved by using 16-hydroxyhexadecanoic acid in 2:1 M excess at 80 °C, yielding a product with 75% copolymer content and average molecular weight higher than 3000 Da. The emulsion-solvent evaporation method allowed the efficient production of nanoparticles based on this copolymer, with sizes around 230 nm, used for the encapsulation of a model bioactive compound, the anticancer drug sorafenib. Production yields of >70% and encapsulation efficiencies of around 60% are very promising for further development of this approach.

Engineering the metabolism and morphology of the filamentous fungus Trichoderma reesei for efficient L-malic acid production

L-malic acid (MA) is a vital platform chemical with huge market demand because of its broad industrial applications. A cell factory for MA production was engineered by strengthening the intrinsic pathway without inserting foreign genes into Trichoderma reesei. The native MA transporter gene in the T. reesei genome was characterized (trmae1), and its overexpression significantly improved MA production, which increased from 2 to 56.24 g/L. Native pyruvate carboxylase, malate dehydrogenase, malic enzyme, and glucose transporter were overexpressed further to improve the titer and yield of MA production. Fungal morphology was adapted to produce MA in the fermenter by deleting gul1. A titer of 235.8 g/L MA was produced from the final engineered strain in a 5-L fermenter with a yield of 1.48 mol of MA per mol of glucose and productivity of 1.23 g/L/h. This study provides novel insights for understanding and remodeling the MA synthesis pathway.

Chemical Constituents, Antioxidant, and α-Glucosidase Inhibitory Activities of Different Fermented Gynostemma Pentaphyllum Leaves and Untargeted Metabolomic Measurement of the Metabolite Variation.

To assess the effects of microbial fermentation on Gynostemma pentaphyllum leaves (GPL), four probiotics were used to ferment GPL (FGPL) for 7 days. At different stages of fermentation, changes in the active components and biological activities of FGPL were determined. The findings suggest that short-term fermentation with probiotics can enhance both the content and bioactivity of active components in GPL. However, prolonged fermentation may lead to a decline in these aspects. Among them, the best effect was observed with SWFU D16 fermentation for 2 days. This significantly improved the total phenolic and total flavonoid content, antioxidant capacity, and inhibitory ability against α-glucosidase activity with an increase of 28%, 114.82%, 7.42%, and 31.8%, respectively. The high-performance liquid chromatography (HPLC) analysis results also supported this trend. Untargeted metabolomics analysis revealed metabolite changes between GPL and FGPL and the key metabolites associated with these functional activities. These key metabolites are mainly organic acids, flavonoids, carbohydrates, terpenoids, and other substances. KEGG analysis demonstrated that microbial metabolism in diverse environments and carbon metabolism were the most significantly enriched pathways. Among them, 3-(3-hydroxyphenyl) propanoic acid, d-glucose, gallic acid, gluconic acid, l-lactic acid, and l-malic acid were mostly involved in the microbial metabolism of diverse environmental pathways. In contrast, D-glucose, gluconic acid, and l-malic acid were mainly related to the carbon metabolism pathway. This study revealed the positive effect of probiotic fermentation on GPL and its potential metabolism mechanism, which could provide supporting data for further research.

Preparation of Thin Film Composite (TFC) Membrane with DESPs Interlayer and Its Forward Osmosis (FO) Performance for Organic Solvent Recovery.

To explore the application of forward osmosis (FO) technology in the organic solvent recovery field, we prepared a new solvent-resistant triple layer thin film composite (TFC) membrane on the PI (polyimide) substrate. The deep eutectic supramolecular polymers (DESPs) interlayer was constructed on the substrate to improve the separation performance and solvent resistance. DESPs interlayer was formed by mixing and heating with cyclodextrin as the hydrogen bond acceptor and L-malic acid as the hydrogen bond donor. The chemical changes, surface property and morphology of the composite membrane with DESPs interlayer were characterized. The separation performance and stability of the triple layer composite membrane in organic solvent FO were studied. For the monascorubrin-ethanol system, the permeation flux of TFC/DESPs5-PI membrane could reach 9.51 LMH while the rejection rate of monascorubrin was 98.4% (1.0 M LiCl/ethanol as draw solution), which was better than the pristine membrane. Therefore, this solvent-resistant triple layer composite FO membrane has good potential for the recovery of organic solvents.

Extraction and Surface Functionalization of Cellulose Nanocrystals from Sugarcane Bagasse.

The present study aimed to optimize the process for extracting cellulose nanocrystals (CNCs) from sugarcane bagasse through ultrasonic-assisted sulfuric acid hydrolysis and its subsequent modification with L-malic acid and silane coupling agent KH-550. The effects of the different modification methods and the order of modification on the structures and properties of bagasse CNCs were explored. The results indicated that the optimal process conditions were achieved at an acid-digestion temperature of 50 °C, a reaction time of 70 min, an ultrasonic power of 250 W, and a volume fraction of 55%. The modified CNCs were analyzed using infrared spectral, X-ray diffraction, and thermogravimetric techniques, which revealed that L-malic acid was attached to the hydroxyl group on the CNCs via ester bond formations, and the silane coupling agent KH-550 was adsorbed effectively on the CNCs' surfaces. Moreover, it was observed that the modification of the CNCs by L-malic acid and the KH-550 silane coupling agent occurred only on the surface, and the esterification-crosslinking modification method provided the best thermal stability. The performance of self-made CNC was found to be superior to that of purchased CNC based on the transmission electron microscopy analysis. Furthermore, the modified esterified-crosslinked CNCs exhibited the best structure and performance, thereby offering a potential avenue for the high-value utilization of sugarcane bagasse, a byproduct of sugarcane sugar production, and the expansion of the comprehensive utilization of sugarcane bagasse.

Co-fermented milk beverage has better stability and contains more health-promoting amino acid metabolites than single-strain-fermented milk beverage over one-month storage

Few studies investigated the effects of co-fermentation with bifidobacteria on post-storage changes of probiotic fermented beverages (PFBs). Thus, this study compared the post-storage changes in physicochemical index and metabolomes of PFBs produced singly by Lacticaseibacillus paracasei PC-01 (PC-01) or in combination with Bifidobacterium adolescentis B8589 (B8589). No significant differences were observed in the pH, titratable acidity, and viable cell counts between the two PFBs over 30-day storage. However, adding B8589 not only increased the stability of PFB (based on evaluating differences in PFBs metabolomics), but also the contents of beneficial amino acid metabolites, including 4-hydroxystyrene, gamma-aminobutyric acid, N-acetyl-l-aspartic acid, d-alanyl-d-alanine, and l-malic acid, after storage. Our study showed that B8589 is preferred to single-strain fermentation by PC-01. This study supports the concept of using bifidobacteria as starter culture in PFB production.

Safety of apple fruit cell culture biomass as a novel food pursuant to Regulation (EU) 2015/2283.

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the safety of an apple fruit cell culture biomass as a novel food (NF) pursuant to Regulation (EU) 2015/2283 and intended as an ingredient for food supplements in adults. The cells have been sourced from the callus grown on a piece of apple placed on a solid medium under sterile conditions. The de-differentiated apple cells are then cultivated in liquid medium. The medium contains sucrose, vitamins, minerals, trace elements and the two synthetic plant hormone analogues, benzylaminopurine (< 0.1 mg/kg) and 2,4-dichlorophenoxyacetic acid (< 0.25 mg/kg). These plant hormones are regulated under the EU pesticide legislation and their residue levels in the NF are in compliance with the EU maximum residue levels. The main components of the NF are carbohydrates (including sugars and non-digestible carbohydrates), ash, proteins and smaller amounts of fatty acids and organic acids. Except for the amount of total fat and the organic acids (succinic and l-malic acid), the quantities of the compositional parameters of the NF and apple have little in common. The Panel considers that a provided subchronic toxicity study was not needed to establish the safety of this NF, when taking into account the source of the NF, i.e. apples, the production process, the low intended use level and the composition of the NF, despite the noted differences to apple. The Panel considers that the NF contains proteins, which were not detected in apple and which may be allergenic. The Panel concludes that the NF, an apple fruit cell culture biomass, is safe under the proposed conditions of use.

Production of L-Malic Acid by Metabolically Engineered Aspergillus nidulans Based on Efficient CRISPR-Cas9 and Cre-loxP Systems.

Aspergillus nidulans has been more extensively characterized than other Aspergillus species considering its morphology, physiology, metabolic pathways, and genetic regulation. As it has a rapid growth rate accompanied by simple nutritional requirements and a high tolerance to extreme cultural conditions, A. nidulans is a promising microbial cell factory to biosynthesize various products in industry. However, it remains unclear for whether it is also a suitable host for synthesizing abundant L-malic acid. In this study, we developed a convenient and efficient double-gene-editing system in A. nidulans strain TN02A7 based on the CRISPR-Cas9 and Cre-loxP systems. Using this gene-editing system, we made a L-malic acid-producing strain, ZQ07, derived from TN02A7, by deleting or overexpressing five genes (encoding Pyc, pyruvate carboxylase; OahA, oxaloacetate acetylhydrolase; MdhC, malate dehydrogenase; DctA, C4-dicarboxylic acid transporter; and CexA, citric acid transporter). The L-malic acid yield in ZQ07 increased to approximately 9.6 times higher (up to 30.7 g/L titer) than that of the original unedited strain TN02A7, in which the production of L-malic acid was originally very low. The findings in this study not only demonstrate that A. nidulans could be used as a potential host for biosynthesizing organic acids, but also provide a highly efficient gene-editing strategy in filamentous fungi.

Physiological, Enological and Agronomic Characterization of Pedro Ximénez Grapevine Cultivar under Organic Farming in a Warm Climate Zone

One of the challenges that European agriculture will have to face will be to adapt conventional agriculture to procedures of the new European agricultural policies. In this way, organic farming will have more importance in the coming years. One of the most important crops worldwide is grapevine. The main objective of this research work focuses on the physiological, agronomic, and enological characterization of Pedro Ximénez with the purpose of knowing the viability of the organic cultivation of this cultivar in a warm climate zone. Two experimental plots were selected with two different types of management, organic and conventional. In both plots, photosynthetic capacity (AN), stomatal conductance (gs), and intrinsic water-use efficiency (WUEi) were measured, and physicochemical composition of grape must was analyzed during ripening. In addition, bunch and pruning weight were measured as agronomic parameters. Physiological results were not significantly different between management at a general level in gs and WUEi, being possible to identify a difference in AN just before the harvest. At the level of fruit ripening, significant differences were found between the two managements. At harvest, grape must had a higher sugar concentration, amine nitrogen (α-NH2), and yeast assimilable nitrogen (YAN) in the organic management than in conventional, where higher values of pH and l-malic acid were observed. Taking into account the preliminary results obtained it could be concluded the viability of the organic management for Pedro Ximénez crop in a warm climate zone.

Recent advances in the production of malic acid by native fungi and engineered microbes.

Malic acid is mainly produced by chemical methods which lead to various environmental sustainability concerns associated with CO2 emissions and resulting global warming. Since malic acid is naturally synthesized, microorganisms offer an eco-friendly and cost-effective alternative for its production. An additional advantage of microbial production is the synthesis of pure L-form of malic acid. Due to its numerous applications, biotechnologically- produced L-malic acid is a much sought-after platform chemical. Malic acid can be produced by microbial fermentation via oxidative/reductive TCA and glyoxylate pathways. This article elaborates the potential and limitations of high malic acid producing native fungi belonging to Aspergillus, Penicillium, Ustilago and Aureobasidium spp. The utilization of industrial side streams and low value renewable substrates such as crude glycerol and lignocellulosic biomass is also discussed with a view to develop a competitive bio-based production process. The major impediments present in the form of toxic compounds from lignocellulosic residues or synthesized during fermentation along with their remedial measures are also described. The article also focuses on production of polymalic acid from renewable substrates which opens up a cost-cutting dimension in production of this biodegradable polymer. Finally, the recent strategies being employed for its production in recombinant organisms have also been covered.

Pyridinic-N-rich carbon dots in IFE-based Turn-off Fluorometric detection of nerve agent Mimic- Diethyl chlorophosphate and multicolor cell imaging.

Fluorometric sensors for the detection of nerve agent mimics have received a lot of interest nowadays due to their high sensitivity and selectivity, ease of operation, and real-time monitoring. Pyridinic-N-rich carbon dots (NCDs) prepared through microwave-assisted pyrolysis of l-Malic acid and urea have been explored first time in this work as a novel turn-off fluorescent probe for the sensitive and selective detection of diethyl chlorophosphate (DCP), a nerve agent mimic. The as-prepared carbon dots contained a large amount of pyridinic nitrogen on their surface, which can modulate the photoluminescence properties of the NCDs. The blue emissive NCDs possessed both excitation wavelength-dependent and independent emission behavior. The detection of DCP was premised on quenching of the fluorescence emission intensity of NCDs in the presence of similar chemical reagents (e.g., trimethyl phosphate, triethyl phosphate, triethyl phosphonoacetate, triphenyl phosphate, diphenyl phosphate, tributyl phosphate). Fluorescence quenching of the NCDs in the presence of DCP has been attributed to the inner filter effect (IFE). From the linear Stern-Volmer plot (R2=0.9992), the limit of detection (LOD) was found to be 84μM for sensing DCP for the concentration ranging between 3 and 15mM. The biocompatibility of NCDs was assessed through cytotoxicity assay on MDA-MB-231 breast cancer cells. Fluorescence imaging demonstrated that NCDs have low cytotoxicity and can be employed successfully in cell imaging.

Effect of temperature on chemical compounds of Cupei (precursor of bran vinegar) during in-situ aging and revelation of functional microorganisms in the process

The precursor of Chinese traditional bran vinegar (Cupei) is usually carried out by in-situ aging to improve the quality. Temperature and microbial activity are potential factors that impact Cupei properties during aging. However, little is known about the effect of temperature on Cupei and the functional microorganisms during this stage. In this study, changes of important compounds and potential functional microorganisms were determined, and the relationships between them were investigated during aging at different constant temperatures. Results showed that free-amino acids (e.g., Leu, Glu, Ala, Ile, Thr, His, and Met), organic acids (e.g., lactic acid, l-malic acid, and phenyllactic acid), sugars, and flavor compounds (e.g., esters, aldehydes, and phenols) of Cupei were significantly impacted by bacterial growth and the Maillard reaction during in-situ aging, which was temperature-specific and time-specific. Based on Illumina sequencing, the Bacillus and Oceanobacillus were revealed to significantly impact the properties of Cupei. B. sporothermodurans, B. oleronius, B. ruris, B. thermoamylovorans and some unidentified Oceanobacillus bacteria that were potential functional bacteria. Furthermore, we proposed gradient constant temperature and bio-perturbation strategies for improving aging efficiency based on this study. Overall, our study provided an understanding of roles of temperature and microbes on in-situ aging of Cupei.

Malolactic fermentation of lactic acid bacteria isolated from southern Brazilian red wine.

The objective was to isolate lactic acid bacteria (LAB) from southern Brazil's wines and investigate their potential as starter cultures for malolactic fermentation (MLF) in Merlot (ME) and Cabernet Sauvignon (CS) wines through the fermentative capacity. The LAB were isolated from CS, ME, and Pinot Noir (PN) wines in the 2016 and 2017 harvests and evaluated for morphological (color and shape of the colonies), genetic, fermentative (increase in pH, acidity reduction, preservation of anthocyanins, decarboxylation of L-malic acid, yield of L-lactic acid, and content of reduced sugars), and sensory characteristics. Four strains were identified as Oenococcus oeni [CS(16)3B1, ME(16)1A1, ME(17)26, and PN(17)65], one as Lactiplantibacillus plantarum [PN(17)75], and one as Paucilactobacillus suebicus [CS(17)5]. Isolates were evaluated in the MLF and compared to a commercial strain (O. oeni), as well as a control (without inoculation and spontaneous MLF), and standard (without MLF). CS(16)3B1 and ME(17)26 isolates finished the MLF for CS and ME wines, respectively, after 35 days, similar to the commercial strain, and CS(17)5 and ME(16)1A1 isolates ended the MLF in 45 days. In the sensory analysis, ME wines with isolated strains received better scores for flavor and overall quality than the control. Compared to the commercial strain, CS(16)3B1 isolate obtained the highest scores for buttery flavor and taste persistence. CS(17)5 isolate received the higher scores for a fruity flavor and overall quality and the lowest for a buttery flavor. The native LAB displayed MLF potential, regardless of the year and grape species from which they were isolated.

Antioxidant Capacity Changes and Untargeted Metabolite Profile of Broccoli during Lactic Acid Bacteria Fermentation

The purpose of this study was to reveal the changes in total phenolic content and antioxidant capacity of broccoli, and an untargeted metabolomics approach was developed to investigate the effect of lactic acid bacteria fermentation on the metabolome of broccoli florets. The results showed that the total phenolic content and antioxidant capacity significantly increased after fermentation. The untargeted metabolite profile showed that the main chemical components of fermented and unfermented broccoli are lipids and lipid-like molecules, organic acids and derivatives and organoheterocyclic compounds. Univariate and multivariate statistical analyses of the identified metabolites showed some metabolites such as sorbitol are upregulated after fermentation, and that other metabolites such as l-malic acid are downregulated after fermentation. Moreover, metabolite pathway analyses were used to study the identification of subtle but significant changes among groups of related metabolites that cannot be observed with conventional approaches. KEGG pathway analysis showed that metabolites are mainly enriched in the glucagon signaling pathway, pyruvate metabolism, glycolysis/gluconeogenesis and fructose and mannose metabolism after fermentation, compared with raw broccoli. The results of this study can help to further our understanding of the impact of LAB fermentation on bioactivity changes in and the metabolites profile of fermented broccoli, and the application of fermented broccoli in health foods and special dietary foods.

Fractionation and characterization of poly(β-L-malic acid) produced by Aureobasidium melanogenum ipe-1

Poly (β-L-malic acid) (PMLA) is attracting industrial interest for its potential application in medicine and other industries, whose functions primarily depend upon its molecular size and chemical structure. Up to now, the fractionation and characterization of PMLA produced by Aureobasidium spp. were still unclear. In this study, the product from A. melanogenum ipe-1 was effectively fractionated using 300 and 50 kDa membranes. During the filtration, the mechanisms of membrane fouling were illegible since the PMLA can both reject and permeate the membrane, while the main fouling mechanism varied between standard blocking and complete blocking during the diafiltration. After fractionation, 14.0, 8.4 and 77.6 % of the PMLAs with Mws of 75,134, 21,344 and 10,056 Da were distributed in the 300 kDa retentate after diafiltrating, 50 kDa retentate after diafiltrating, and the 50 kDa permeate, respectively. The Mw/Mns of the PMLAs were 4.12, 1.92, and 1.12 in the three fractions. Based on characteristic spectra of NMR, HPLC and FTIR, the product was not usual L-malic acid monomers, but glucose-terminated PMLA. The glucose was located at the terminal hydroxyl of PMLA. These results would serve as a valuable guide for process design and practical operation in subsequent industrial application.