Targeted 1-H-NMR wine analyses revealed specific metabolomic signatures of yeast populations belonging to the Saccharomyces genus

This study aimed to explore the non-volatile metabolomic variability of a large panel of strains (44) belonging to the Saccharomyces cerevisiae and Saccharomyces uvarum species in the context of the wine alcoholic fermentation. For the S. cerevisiae strains flor, fruit and wine strains isolated from different anthropic niches were compared. This phenotypic survey was achieved with a special focus on acidity management by using natural grape juices showing opposite level of acidity. A 1H NMR based metabolomics approach was developed for quantifying fifteen wine metabolites that showed important quantitative variability within the strains. Thanks to the robustness of the assay and the low amount of sample required, this tool is relevant for the analysis of the metabolomic profile of numerous wines. The S. cerevisiae and S. uvarum species displayed significant differences for malic, succinic, and pyruvic acids, as well as for glycerol and 2,3-butanediol production. As expected, S. uvarum showed weaker fermentation fitness but interesting acidifying properties. The three groups of S. cerevisiae strains showed different metabolic profiles mostly related to their production and consumption of organic acids. More specifically, flor yeast consumed more malic acid and produced more acetic acid than the other S. cerevisiae strains which was never reported before. These features might be linked to the ability of flor yeasts to shift their metabolism during wine oxidation.

Effect of organic acids on fermentation quality and microbiota of horseshoe residue and corn protein powder

This experiment aimed to investigate the impact of malic acid (MA) and citric acid (CA) on the nutritional composition, fermentation quality, rumen degradation rate, and microbial diversity of a mixture of apple pomace and corn protein powder during ensiling. The experiment used apple pomace and corn protein powder as raw materials, with four groups: control group (CON), malic acid treatment group (MA, 10 g/kg), citric acid treatment group (CA, 10 g/kg), and citric acid + malic acid treatment group (MA, 10 g/kg + CA, 10 g/kg). Each group has 3 replicates, with 2 repetitions in parallel, subjected to mixed ensiling for 60 days. The results indicated: (1) Compared to the CON group, the crude protein content significantly increased in the MA, CA, and MA + CA groups (p < 0.05), with the highest content observed in the MA + CA group. The addition of MA and CA effectively reduced the water-soluble carbohydrate (WSC) content (p < 0.05). Simultaneously, the CA group showed a decreasing trend in NDFom and hemicellulose content (p = 0.08; p = 0.09). (2) Compared to the CON group, the pH significantly decreased in the MA, CA, and MA + CA groups (p < 0.01), and the three treatment groups exhibited a significant increase in lactic acid and acetic acid content (p < 0.01). The quantity of lactic acid bacteria increased significantly (p < 0.01), with the MA + CA group showing a more significant increase than the MA and CA groups (p < 0.05). (3) Compared to the CON group, the in situ dry matter disappearance (ISDMD) significantly increased in the MA, CA, and MA + CA groups (p < 0.05). All three treatment groups showed highly significant differences in in situ crude protein disappearance (ISCPD) compared to the CON group (p < 0.01). (4) Good's Coverage for all experimental groups was greater than 0.99, meeting the conditions for subsequent sequencing. Compared to the CON group, the Shannon index significantly increased in the CA group (p < 0.01), and the Simpson index increased significantly in the MA group (p < 0.05). However, there was no significant difference in the Chao index among the three treatment groups and the CON group (p > 0.05). At the genus level, the abundance of Lentilactobacillus in the MA, CA, and MA + CA groups was significantly higher than in the control group (p < 0.05). PICRUSt prediction results indicated that the metabolic functional microbial groups in the CA and MA treatment groups were significantly higher than in the CON group (p < 0.05), suggesting that the addition of MA or CA could reduce the loss of nutritional components such as protein and carbohydrates in mixed ensilage. In conclusion, the addition of malic acid and citric acid to a mixture of apple pomace and corn protein powder during ensiling reduces nutritional losses, improves fermentation quality and rumen degradation rate, enhances the diversity of the microbial community in ensiled feed, and improves microbial structure. The combined addition of malic acid and citric acid demonstrates a superior effect.

SpCTP3 from the hyperaccumulator Sedum plumbizincicola positively regulates cadmium tolerance by interacting with SpMDH1

Cadmium (Cd) is a heavy metal pollutant mainly originating from the discharge of industrial sewage, irrigation with contaminated water, and the use of fertilizers. The phytoremediation of Cd polluted soil depends on the identification of the associated genes in hyperaccumulators. Here, a novel Cd tolerance gene (SpCTP3) was identified in hyperaccumulator Sedum plumbizincicola. The results of Cd2+ binding and thermodynamic analyses, revealed the CXXC motif in SpCTP3 functions is a Cd2+ binding site. A mutated CXXC motif decreased binding to Cd by 59.93%. The subcellular localization analysis suggested that SpCTP3 is primarily a cytoplasmic protein. Additionally, the SpCTP3-overexpressing (OE) plants were more tolerant to Cd and accumulated more Cd than wild-type Sedum alfredii (NHE-WT). The Cd concentrations in the cytoplasm of root and leaf cells were significantly higher (53.75% and 71.87%, respectively) in SpCTP3-OE plants than in NHE-WT. Furthermore, malic acid levels increased and decreased in SpCTP3-OE and SpCTP3-RNAi plants, respectively. Moreover, SpCTP3 interacted with malate dehydrogenase 1 (MDH1). Thus, SpCTP3 helps regulate the subcellular distribution of Cd and increases Cd accumulation when it is overexpressed in plants, ultimately Cd tolerance through its interaction with SpMDH1. This study provides new insights relevant to improving the Cd uptake by Sedum plumbizincicola.

Malic acid inhibits accumulation of cadmium, lead, nickel and chromium by down-regulation of OsCESA and up-regulation of OsGLR3 in rice plant

Malic acid (MA) plays an important role in plant tolerance to toxic metals, but its effect in restricting the transport of harmful metals remains unclear. In this study, japonica rice NPB and its fragile-culm mutant fc8 with low cellulose and thin cell wall were used to investigate the influence of MA on the accumulation of 4 toxic elements (Cd, Pb, Ni, and Cr) and 8 essential elements (K, Mg, Ca, Fe, Mn, Zn, Cu and Mo) in rice. The results showed that fc8 accumulated less toxic elements but more Ca and glutamate in grains and vegetative organs than NPB. After foliar application with MA at rice anthesis stage, the content of Cd, Pb, Ni significantly decreased by 27.9-41.0%, while those of Ca and glutamate significantly increased in both NPB and fc8. Therefore, the ratios between Cd and Ca in grains of NPB (3.4‰) and fc8 (1.5‰) were greatly higher than that in grains of NPB + MA (1.1‰) and fc8+MA (0.8‰) treatments. Meanwhile, the expression of OsCEAS4,7,8,9 for the cellulose synthesis in secondary cell walls were down-regulated and cellulose content in vegetative organs of NPB and fc8 decreased by 16.7-21.1%. However, MA application significantly up-regulated the expression of GLR genes (OsGLR3.1-3.5) and raised the activity of glutamic-oxalacetic transaminease for glutamate synthesis in NPB and fc8. These results indicate that hazard risks of toxic elements in foods can be efficiently reduced through regulating cellulose biosynthesis and GLR channels in plant by combining genetic modification in vivo and malic acid application in vitro.

Characterization and bioaccessibility assessment of bioactive compounds from camu-camu (Myrciaria dubia) powders and their food applications

Camu-camu (Myrciaria dubia) is a tropical fruit known for its content of bioactive compounds. This study aimed to evaluate physicochemically, morphologically, andsensorialpowders from camu-camu obtained by spray-drying at two inlet temperatures (150 °C and 180 °C) with three encapsulating agents (maltodextrin, whey protein and a 50:50 mixture of both) and by freeze-drying of whole fruit. The use of maltodextrin protected bet anthocyanins (cyanidin-3-glucoside (C3G) and delphinidin-3-glucoside (D3G)), but whey protein showed a better protective effect on ascorbic and malic acids. These facts were confirmed during the storage stability test, finding that relative humidity is a critical variable in preserving the bioactive compounds of camu-camu powders. The powders with the highest content of bioactive compounds were added to a yogurt and a white grape juice, and then sensory evaluated. The bioaccessibility studies in gastric and intestinal phases showed better recovery percentages of bioactive compounds in camu-camu powders (up to 60.8 %) and beverages (up to 90 %) for C3G, D3G, ascorbic acid, and malic acid than in the fruit juice. Dehydration of camu-camu (M. dubia) is a strategy to increase the bioactive compounds stability, modulate the fruit sensory properties, and improve their bioavailability after incorporation in food matrices.

The release of Cd, Cu, Fe, Mn, Ni, Pb, and Zn from clay loam and sandy loam soils under the influence of various organic amendments and low-molecular-weight organic acids

Low-molecular-weight organic acids (LMWOAs) interact with potentially toxic elements (PTEs) and affect their mobility; however, the effect of different amendments on PTEs release from soils when added along with LMWOAs is still unclear. In this study, two soils (a clay loam and a sandy loam) amended with sugar beet bagasse ash (SBBA), poultry manure (PM), sewage sludge (SS) from Kermanshah city (SSK), and SS from Toyserkan city (SST) at a rate of 5 %. In these treatments we studied release of Cd, Cu, Fe, Mn, Ni, Pb, and Zn with citric, oxalic, and malic acids added at 10 different rates each, i.e., 0.1, 1, 2.5, 5, 10, 30, 40, 50, 70, and 100 mmol L-1. We found that the percentage of PTEs release was higher for citric, followed by oxalic and malic acids. The highest amount of PTEs released in both soils decreased in the following order: SST > SBBA > SSK > PM. The percentage of PTEs complexed with LMWOAs and the log activity of PTEs species mostly increased with decreasing pH. It could be concluded that the application of PM is more environmentally friendly than that of the other amendments. Since Cd had the highest percentage of release in all treated soils and LMWOAs, more consideration should be given to Cd to prevent environmental pollution.

Application of Schizosaccharomyces japonicus in makgeolli fermentation and its brewing characteristics

Recently, unconventional yeasts have become popular as fermentation starters in the brewing industry due to the growing consumer demand for aromatic diversity. Specifically, Schizosaccharomyces japonicus has been explored as a potential starter culture for beer and wine production because of its distinct brewing characteristics; however, its application in makgeolli fermentation has not been tested. Therefore, in the present study, two Sz. japonicus strains (SZJ-1 and SZJ-2) were isolated from natural sources, and their brewing characteristics for makgeolli fermentation were compared with those of commercial S. cerevisiae strain. Although the tested isolates showed a lower fermentation and carbon source consumption rate than control-, their overall alcohol fermentation characteristics were suitable for makgeolli production. Regarding flavor composition, Sz. japonicus-fermented makgeolli possessed more ester compounds (e.g., 2-phenylethyl acetate, ethyl acetate, and ethyl decanoate) than S. cerevisiae-fermented makgeolli. Therefore, Sz. japonicus can be used as an alternative culture starter in makgeolli fermentation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01265-6.

Exogenously applied zinc improves sugar-acid profile of loquat (Eriobotrya japonica Lindl.) by regulating enzymatic activities and expression of their metabolism-related genes

Soluble sugars and organic acids are the most abundant components in ripe fruits, and they play critical roles in the development of fruit flavor and taste. In this study, loquat trees were sprayed with 0.1, 0.2 and 0.3% zinc sulphate. The contents of soluble sugars and organic acids were determined using HPLC-RID and UPLC-MS, respectively. The activities of key enzymes involved in sugar-acid metabolism were measured and expression profiling of related genes was done using RT-qPCR. The results revealed that 0.1% zinc sulphate was a promising treatment among other Zn applications with respect to the increased levels of soluble sugars and decreased acid contents in loquats. Correlation analysis showed that the enzymes i.e., SPS, SS, FK, and HK were may be involved in the regulation of fructose and glucose metabolism in the fruit pulp of loquat. While, the activity of NADP-ME showed negative and NAD-MDH showed a positive correlation with malic acid content. Meanwhile, EjSPS1-4, EjSS2-4, EjHK1-3, and EjFK1-6 may play an important role in soluble sugar metabolism in the pulp of loquat fruits. Similarly, EjPEPC2, EjPEPC3, EjNAD-MDH1, EjNAD-MDH3-5, EjNAD-MDH6 and EjNAD-MDH13 may have a vital contribution to malic acid biosynthesis in loquat fruits. This study provides new insights for future elucidation of key mechanisms regulating soluble sugars and malic acid biosynthesis in loquats.

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.

New malic acid producer strains of Saccharomyces cerevisiae for preserving wine acidity during alcoholic fermentation

In the context of climate change, the chemical composition of wines is characterized by a massive drop of malic acid concentration in grape berries. Then wine professionals have to find out physical and/or microbiological solutions to manage wine acidity. The aim of this study is to develop wine Saccharomyces cerevisiae strains able to produce significant amount of malic acid during the alcoholic fermentation. By applying a large phenotypic survey in small scale fermentations, the production level of malic acid in seven grape juices confirmed the importance of the grape juice in the production of malic acid during the alcoholic fermentation. Beside the grape juice effect, our results demonstrated that extreme individuals able to produce up to 3 g/L of malic acid can be selected by crossing together appropriate parental strains. A multivariate analysis of the dataset generated illustrate that the initial the amount of malic acid produced by yeast is a determining exogenous factor for controlling the final pH of wine. Interestingly most of the acidifying strains selected are particularly enriched in alleles that have been previously reported for increasing the level of malic acid at the end of the alcoholic fermentation. A small set of acidifying strains were compared with strains able to consume a large amount of malic acid previously selected. The total acidity of resulting wines was statistically different and a panelist of 28 judges was able to discriminate the two groups of strains during a free sorting task analysis.

Enhanced immobility of Pb(II) during ferrihydrite-Pb(II) coprecipitates aging impacted by malic acid or phosphate

Metastable ferrihydrite is omnipresent in environments and can influence the fate of Pb(II) during ferrihydrite transformation. Ferrihydrite is rarely pure and often coexists with impurities, which may influence the mineralogical changes of ferrihydrite and Pb(II) behavior. In this work, we investigated the effect of malic acid or phosphate on Pb(II)-ferrihydrite coprecipitates (Fh-Pb) transformation and the subsequent fate of Pb(II) during the 10-day aging of Fh-Pb. Results showed that both malic acid and phosphate retarded Fh-Pb transformation and prevented the release of Pb(II) from Fh-Pb back into solutions. Pb(II) was beneficial to goethite formation by inhibiting hematite formation while both malic acid and phosphate inhibited goethite formation since they could act as templates of nucleation. Besides, malic acid and phosphate improved the proportion of non-extracted Pb(II) during Fh-Pb transformation, indicating that Pb(II) was incorporated into secondary minerals. Pb(II) could not replace Fe(III) within the crystal lattice due to its large radius but was occluded into pores and defect structures within the secondary mineral lattices. This work can advance our understanding of the influences of malic acid and phosphate on Pb(II) immobility during Fh-Pb aging.

Attenuation of hexaconazole induced oxidative stress by folic acid, malic acid and ferrocenecarboxaldehyde in an invertebrate model Bombyx mori

Fungicides are a class of pesticides used to ward off fungal diseases from agricultural crops to achieve maximum productivity. These chemicals are quite efficient in controlling diseases; however, the excessive use of these affects non-target organisms as well. In this study, Bombyx mori was utilized to investigate the effect of the pesticide hexaconazole (HEX) on the antioxidant system of this organism and also to find ways to mitigate it. On oral exposure to this chemical, a significant reduction in antioxidants, CAT, GPX, GSH, and SOD in the gut, fat body, and silk gland was observed. The HEX treatment also resulted in lipid peroxidation (LPO) in all the three tissues. To mitigate this toxicity and protect the silkworm from oxidative stress, we tested three compounds, namely folic acid, ferrocenecarboxaldehyde, and malic acid having known antioxidant potential. Folic acid provided significant protection against HEX-induced toxicity. Ferrocenecarboxaldehyde and malic acid proved to be ill-efficient in controlling oxidative stress, with ferrocenecarboxaldehyde being the least effective of the three. Folic acid was also efficient in controlling LPO up to a considerable level. Ferrocenecarboxaldehyde and malic acid also prevented LPO less efficiently than folic acid. Overall folic acid was the only compound that mitigated HEX-induced oxidative stress in silkworm with statistical significance in all the tissues viz. gut, fat body, and silk gland.

Valorization of quince peel into functional food ingredients: A path towards "zero waste" and sustainable food systems

Quince (Cydonia oblonga Mill.) is an astringent fruit widely processed into marmalade and other sweets through processes that discard the peel as a by-product. Therefore, this study was performed to characterize the quince peel composition in nutrients and phytochemicals and evaluate its in vitro biological activity, following a “zero waste” approach. The quince peel dry powder was particularly rich in fiber (20.2 g/100 g), fructose (34 g/100 g), malic acid (7.2 g/100 g), and potassium (692 mg/100 g). Extracts prepared by dynamic hydroethanolic maceration and hot water extraction yielded 4.70 and 4.27 mg/g of phenolic compounds, respectively, with a prevalence of flavan-3-ols. The hydroethanolic extract was the most effective in inhibiting lipid peroxidation and oxidative hemolysis, and also presented better antimicrobial effects against foodborne pathogens, which agreed with the highest flavan-3-ol contents. The extracts were better than control synthetic food additives against some tested fungal and bacterial strains. On the other hand, no ability to inhibit nitric oxide production or toxicity to the tumor and non-tumor cell lines was observed. Furthermore, the solid residues remaining after extraction contained 35–37 g/100 g of fiber. Overall, quince peel can be upcycled into fiber-rich and bioactive ingredients to endow the value chain with natural food fortifiers, preservatives, and health promoters.

Quantitative trait loci analysis of glucosinolate, sugar, and organic acid concentrations in Eruca vesicaria subsp. sativa

Eruca vesicaria subsp. sativa is a leafy vegetable of the Brassicaceae family known for its pungency. Variation in growing conditions, leaf age, agronomic practices, and variety choice lead to inconsistent quality, especially in content of isothiocyanates (ITCs) and their precursor glucosinolates (GSLs). We present the first linkage and Quantitative Trait Loci (QTL) map for Eruca, generated using a population of 139 F4 lines. A significant environmental effect on the abundance of primary and secondary metabolites was observed, with UK-grown plants containing significantly higher concentrations of glucoraphanin, malic acid, and total sugars. Italian-grown plants were characterized by higher concentrations of glucoerucin, indolic GSLs, and low monosaccharides. 20 QTL were identified and associated with robust SNP markers. Five genes putatively associated with the synthesis of the GSL 4-methoxyglucobrassicin (4MGB) were identified as candidate regulators underlying QTL. Analysis revealed that orthologs of MYB51, IGMT1 and IGMT4 present on LG1 are associated with 4MGB concentrations in Eruca. This research illustrates the utility of the map for identifying genes associated with nutritional composition in Eruca and its value as a genetic resource to assist breeding programs for this leafy vegetable crop.

Allantoin overaccumulation enhances production of metabolites under excess of metals but is not tightly regulated by nitric oxide

The aln-3 mutant overaccumulating allantoin and respective wild type (WT) strain of Arabidopsis thaliana were exposed to cadmium (Cd) or mercury (Hg) with or without nitric oxide (NO) donor (sodium nitroprusside, SNP) to study cross-talk, metabolic and oxidative changes between these nitrogen sources (organic vs. inorganic). The aln-3 accumulated over 10-fold more allantoin than WT with the effect of Cd and Hg differing in leaf and root tissue: aln-3 contained more ascorbic acid and phytochelatins when treated with Cd or Hg and more Cd in both organs. SNP depleted leaf Cd and root Hg accumulation in aln3 but had a positive impact on the amount of metabolites typically in WT plants, indicating potentially negative relation between allantoin and NO. In agreement, aln-3 roots showed lower NO signals in control or metal treatments, but higher ROS signal, and SNP had more pronounced impact in WT roots. Flavonol glycosides were more abundant in aln-3 and were affected more by metals than by SNP. Malate was the most affected Krebs acid with strong reaction to SNP and Hg treatment. Data indicate that allantoin overaccumulation influences the accumulation of specific metabolites but nitric oxide has a greater impact on the metabolite profile in WT.

Expression of Escherichia coli malic enzyme gene in Zymomonas mobilis for production of malic acid

Malic acid is one of the organic acids which is used in various industries including food and pharmaceuticals. Biotechnological production of malic acid by an efficient microorganism is highly desirable as the process will be eco-friendly and cost-effective. In this study, malic acid synthesis by Zymomonas mobilis was studied by expressing Escherichia coli malic enzyme gene under Pchap, Ptac and Ppdc promoters. The mae⁺ recombinants were obtained by recombineering-based genomic integration of Pchap-mae, Ptac-mae and Ppdc-mae sequences. The Ppdc promoter showed the highest expression of malic enzyme and the Pchap the lowest. However, cell growth was limited in mae⁺ recombinant containing Ppdc promoter. The metabolic analysis showed the highest level of malic acid in Ppdc-mae recombinant (2.84 g/L), which was about eight times higher than that in the wild type strain. The study showed that these three promoters can be used to produce organic acids in Z. mobilis.

Antibiofilm activity of the biosurfactant and organic acids against foodborne pathogens at different temperatures, times of contact, and concentrations

Biofilm formation has been suggested to play a significant role in the survival of pathogens in food production. Interest in evaluating alternative products of natural origin for disinfectant use has increased. However, there is a lack of information regarding the effects of biosurfactants and organic acids on Salmonella enterica serotype Enteritidis, Escherichia coli, and Campylobacter jejuni biofilms, mainly considering temperatures found in environments of poultry processing, as well as simulating the contact times used for disinfection. The aim of this study was to evaluate the antibiofilm activity of rhamnolipid, malic acid, and citric acid on the adhesion of S. Enteritidis, E. coli, and C. jejuni on polystyrene surfaces at different temperatures (4, 12, and 25 °C), compound concentrations, and times of contact (5 and 10 min), and to analyze the potential use of these compounds to disrupt formed biofilms. All three compounds exhibited antibiofilm activity under all analyzed conditions, both in the prevention and removal of formed biofilms. Contact time was less important than temperature and concentration. The antibiofilm activity of the compounds also varied according to the pathogens involved. In the food industry, compound selection must consider the temperature found in each stage of product processing and the target pathogens to be controlled.

Techno economic analysis of malic acid production using crude glycerol derived from waste cooking oil

In the present work, Aspergillus niger was employed to produce commercially valuable malic acid from crude glycerol derived from waste cooking oil. Crude glycerol dosage, yeast extract dosage and initial pH were the influencing factors playing a significant role in the malic acid synthesis. The optimal condition for malic acid biosynthesis was studied by using response surface methodology. Further the feasibility analysis for biosynthesis of malic acid from crude glycerol was studied using the laboratory scale optimized data, with this experimentally optimized data, plant was simulated using SuperPro Designer (v10). The cost involved for malic acid synthesis per unit volume was likely expected to be $0.43/kg of malic acid using reactive extraction method. Thus, process optimization combined with techno-economical analysis of malic acid production could be beneficial.

Electroplating of HAp-brushite coating on metallic bioimplants with advanced hemocompatibility and osteocompatibility properties

In cases of severe bone tissue injuries, the use of metallic bioimplants is quite widespread due to their high strength, high fracture toughness, hardness, and corrosion resistance. However, they lack adequate biocompatibility and show poor metal-tissue integration during the post-operative phase. To mitigate this drawback, it is beneficial to add a biocompatible polymer layer to ensure a quick growth of cell or tissue over the surface of metallic bioimplant material. Furthermore, this additional layer should possess good adherence with the underlying material and also accompany a rapid bonding between the tissue and the implant material, in order to reduce the recovery time for the patient. Therefore, in this work, we report a novel green electroplating route for growing porous hydroxyapatite-brushite coatings on a stainless steel surface. The malic acid used for the production of hydroxyapatite-brushite coatings has been obtained from an extract of locally available apple fruit (Malus domestica). We demonstrate the effect of electroplating parameters on the structural morphology of the electroplated composite layer via XRD, SEM with EDS, and FTIR characterization techniques and report an optimized set of electroplating parameters that will yield the best composite coating in terms of thickness, adherence to substrate and speed. The hemocompatibility and osteocompatibility studies on the electroplated composites coating show this technology's effectiveness and potential applicability in biomedical applications. Compared to other routes reported in the literature, this electroplating route is quicker and yields better composite coatings with faster bone tissue growth potential.

Effect of supplementing Leucaena leucocephala leaves alone or in conjunction with malic acid on nutrient utilization, performance traits, and enteric methane emission in crossbred calves under tropical conditions

Dietary strategies aiming at minimizing enteric methane (CH₄) emission in ruminants are of practical interest from nutritional, economical, and environmental point of view. The present study evaluated the effects of supplementing Leucaena leucocephala leaves either alone or in conjunction with malic acid on nutrient utilization, growth performance, and enteric CH₄ emission in crossbred cattle fed wheat straw and concentrate-based diet under tropical conditions. Eighteen crossbred (Karan-Fries) calves were randomly allocated into 3 groups: G-I (control)-fed wheat (Triticum aestivum) straw and concentrate mixture in the ratio 50:50; G-II-fed wheat straw, concentrate mixture, and Leucaena leucocephala leaves in the ratio 45:45:10; and (3) G-III-fed similar diet like G-II with an additional supplementation of 1% malic acid on dry matter intake basis. Experimental feeding spanning 90 days included a 7-day metabolism trial and CH₄ quantification study by sulfur hexafluoride tracer technique. Results revealed no significant effect of dietary treatments on dry matter intake (DMI) and digestibility of nutrients, except neutral detergent fiber (NDF) digestibility which was 5.5% higher (P < 0.05) in G-III as compared to control. Further, nitrogen (N) metabolism, rumen microbial protein synthesis, and growth performance remained similar among the treatments. No significant effect was also observed for enteric CH₄ emission (expressed as g/day and g/kg DMI) in calves supplemented with Leucaena leucocephala leaves and malic acid. Therefore, the present findings depict modest improvement in fiber digestibility with no encouraging effect in mitigating enteric CH₄ in growing cattle calves by supplementing Leucaena leucocephala leaves alone or with malic acid within the selected levels.

Coordination of consolidated bioprocessing technology and carbon dioxide fixation to produce malic acid directly from plant biomass in Myceliophthora thermophila

BACKGROUND

Consolidated bioprocessing (CBP) technique is a promising strategy for biorefinery construction, producing bulk chemicals directly from plant biomass without extra hydrolysis steps. Fixing and channeling CO₂ into carbon metabolism for increased carbon efficiency in producing value-added compounds is another strategy for cost-effective bio-manufacturing. It has not been reported whether these two strategies can be combined in one microbial platform.

RESULTS

In this study, using the cellulolytic thermophilic fungus Myceliophthora thermophila, we designed and constructed a novel biorefinery system DMCC (Direct microbial conversion of biomass with CO₂ fixation) through incorporating two CO₂ fixation modules, PYC module and Calvin-Benson-Bassham (CBB) pathway. Harboring the both modules, the average rate of fixing and channeling ¹³CO₂ into malic acid in strain CP51 achieved 44.4, 90.7, and 80.7 mg/L/h, on xylose, glucose, and cellulose, respectively. The corresponding titers of malic acid were up to 42.1, 70.4, and 70.1 g/L, respectively, representing the increases of 40%, 10%, and 7%, respectively, compared to the parental strain possessing only PYC module. The DMCC system was further improved by enhancing the pentose uptake ability. Using raw plant biomass as the feedstock, yield of malic acid produced by the DMCC system was up to 0.53 g/g, with ¹³C content of 0.44 mol/mol malic acid, suggesting DMCC system can produce 1 t of malic acid from 1.89 t of biomass and fix 0.14 t CO₂ accordingly.

CONCLUSIONS

This study designed and constructed a novel biorefinery system named DMCC, which can convert raw plant biomass and CO₂ into organic acid efficiently, presenting a promising strategy for cost-effective production of value-added compounds in biorefinery. The DMCC system is one of great options for realization of carbon neutral economy.

ISTR5

Syringyl monomeric units are the most common intermediates encountered during hardwood lignin degradation. In the present study, efficient utilization of syringaldehyde (SAld), syringic acid (SAc) by Burkholderia sp. ISTR5 (R5) has been shown. The proteogenomic analysis of Burkholderia sp. ISTR5 was done to understand the enzymes involved in the degradation of syringaldehyde and syringic acid. Various proteins such as aldehyde dehydrogenase, laccase, and oxidoreductases were highly upregulated during growth on syringaldehyde and syringic acid. R5 completely transformed both the substrates SAld and SAc to other hydrocarbons in 48 h and 24 h, respectively. Moreover, bioconversion of syringyl lignins followed an unusual pathway and accumulated a considerable amount of industrially valuable chemical malic acid in the reaction titer. This study shows the robust chassis of R5 to cope with the aromatic aldehydic stress and simultaneous bioconversion into valuable products for an efficient biorefinery.

Enhanced malic acid production using Aspergillus niger coupled with in situ product recovery

In the present investigation, recovery of malic acid from the fermentation broth was performed by using in situ reactive extraction method employing different combination of amine and solvent systems. Totally six solvent mixtures were tested for toxicity on Aspergillus niger PJR1. Further, effect of solvent mixture concentration on separation of malic acid was investigated. Solvent system consisting of 2 M of trioctylamine in 1-octanol was found to be non-toxic to A. niger PJR1 and resulted in the maximum partition coefficient of 0.75 when the solvent mixture to liquid ratio of 1:2 used. A. niger PJR1 from crude glycerol using in situ reactive batch fermentation resulted in the maximum malic acid titer of 115.67 ± 3.5 g/L with the productivity of 0.53 g/L.h after 216 h. Further, fed batch extractive fermentation with crude glycerol resulted in malic acid titer of 131.48 ± 3.4 g/L with the productivity of 0.45 g/L.h after 288 h. Thus reactive extraction combined with in situ fermentation could become effective method for enhanced malic acid production.

N-Benzylation of 6-aminoflavone by reductive amination and efficient access to some novel anticancer agents via topoisomerase II inhibition

Series of novel N-benzyl derivatives of 6-aminoflavone (9a-n) were synthesized and evaluated for anticancer and topoisomerase II enzyme inhibition activity. All the synthesized compounds were screened for in vitro anticancer activity against human breast cancer cell line (MCF-7) and human lung cancer cell line (A-549). Among the synthesized compounds, 9f and 9g were found to be the most potent anticancer agents against human breast cancer cell line (MCF-7) with IC₅₀ values of 9.35 µM and 9.58 µM, respectively. Compounds 9b, 9c and 9n exhibited promising anticancer activity against human lung cancer cell line (A-549) with 43.71%, 46.48% and 44.26% inhibition at the highest concentration of 10 µM, respectively. Compounds 9c, 9f and 9g have ability to inhibit the topoisomerase II enzyme. Compound 9f showed most potent topoisomerase II enzyme inhibition activity with IC₅₀ value of 12.11 µM. Further, these compounds have a high potential to be developed as a promising topoisomerase II inhibitors.

Biochemical conversion of biodiesel by-product into malic acid: A way towards sustainability

Crude glycerol, one of the ever-growing by-product of biodiesel industry and is receiving the closest review in recent times because direct disposal of crude glycerol may emerge ecological issues. The renewability, bioavailability and typical structure of glycerol, therefore, discover conceivable application in serving the role of carbon and energy source for microbial biosynthesis of high value products. This conceivable arrangement could find exploitation of crude glycerol as a renewable building block for bio-refineries as it is economically as well as environmentally profitable. In this review, we summarize the uptake and catabolism of crude glycerol by different wild and recombinant microorganism. The chemical and biochemical transformation of crude glycerol into high esteem malic acid by various microbial pathways is also additionally discussed. An extensive investigation in the synthesis of high-value malic acid production from various feed stock which finds applications in cosmeceutical and chemical industries, food and beverages, and to some extent in the field of medical science is also likewise studied. Finally, the open doors for unrefined crude glycerol in serving as a promising abundant energy source for malic acid production in near future have been highlighted.

Dissecting cellobiose metabolic pathway and its application in biorefinery through consolidated bioprocessing in Myceliophthora thermophila

Background

Lignocellulosic biomass has long been recognized as a potential sustainable source for industrial applications. The costs associated with conversion of plant biomass to fermentable sugar represent a significant barrier to the production of cost-competitive biochemicals. Consolidated bioprocessing (CBP) is considered a potential breakthrough for achieving cost-efficient production of biomass-based fuels and commodity chemicals. During the degradation of cellulose, cellobiose (major end-product of cellulase activity) is catabolized by hydrolytic and phosphorolytic pathways in cellulolytic organisms. However, the details of the two intracellular cellobiose metabolism pathways in cellulolytic fungi remain to be uncovered.

Results

Using the engineered malic acid production fungal strain JG207, we demonstrated that the hydrolytic pathway by β-glucosidase and the phosphorolytic pathway by phosphorylase are both used for intracellular cellobiose metabolism in Myceliophthora thermophila, and the yield of malic acid can benefit from the energy advantages of phosphorolytic cleavage. There were obvious differences in regulation of the two cellobiose catabolic pathways depending on whether M. thermophila JG207 was grown on cellobiose or Avicel. Disruption of Mtcpp in strain JG207 led to decreased production of malic acid under cellobiose conditions, while expression levels of all three intracellular β-glucosidase genes were significantly up-regulated to rescue the impairment of the phosphorolytic pathway under Avicel conditions. When the flux of the hydrolytic pathway was reduced, we found that β-glucosidase encoded by bgl1 was the dominant enzyme in the hydrolytic pathway and deletion of bgl1 resulted in significant enhancement of protein secretion but reduction of malate production. Combining comprehensive manipulation of both cellobiose utilization pathways and enhancement of cellobiose uptake by overexpression of a cellobiose transporter, the final strain JG412Δbgl2Δbgl3 produced up to 101.2 g/L and 77.4 g/L malic acid from cellobiose and Avicel, respectively, which corresponded to respective yields of 1.35 g/g and 1.03 g/g, representing significant improvement over the starting strain JG207.

Conclusions

This is the first report of detailed investigation of intracellular cellobiose catabolism in cellulolytic fungus M. thermophila. These results provide insights that can be applied to industrial fungi for production of biofuels and biochemicals from cellobiose and cellulose.

Disruption of a putative mitochondrial oxaloacetate shuttle protein in Aspergillus carbonarius results in secretion of malic acid at the expense of citric acid production

BACKGROUND

In filamentous fungi, transport of organic acids across the mitochondrial membrane is facilitated by active transport via shuttle proteins. These transporters may transfer different organic acids across the membrane while taking others the opposite direction. In Aspergillus niger, accumulation of malate in the cytosol can trigger production of citric acid via the exchange of malate and citrate across the mitochondrial membrane. Several mitochondrial organic acid transporters were recently studied in A. niger showing their effects on organic acid production.

RESULTS

In this work, we studied another citric acid producing fungus, Aspergillus carbonarius, and identified by genome-mining a putative mitochondrial transporter MtpA, which was not previously studied, that might be involved in production of citric acid. This gene named mtpA encoding a putative oxaloacetate transport protein was expressed constitutively in A. carbonarius based on transcription analysis. To study its role in organic acid production, we disrupted the gene and analyzed its effects on production of citric acid and other organic acids, such as malic acid. In total, 6 transformants with gene mtpA disrupted were obtained and they showed secretion of malic acid at the expense of citric acid production.

CONCLUSION

A putative oxaloacetate transporter gene which is potentially involved in organic acid production by A. carbonarius was identified and further investigated on its effects on production of citric acid and malic acid. The mtpA knockout strains obtained produced less citric acid and more malic acid than the wild type, in agreement with our original hypothesis. More extensive studies should be conducted in order to further reveal the mechanism of organic acid transport as mediated by the MtpA transporter.

Green fluorescent carbon quantum dots functionalized with polyethyleneimine, and their application to aptamer-based determination of thrombin and ATP

Brightly fluorescent carbon quantum dots coated with polyethylenimine (PEI-CDs) were prepared using malic acid and PEI as the precursors. The PEI-CDs have a high quantum yield (41%) and green emission (peaking at 502 nm under 430 nm excitation), both of which are not affected by high ionic strength. The PEI-CDs have a positive charge at physiological pH values and can electrostatically bind aptamers with their negative charge. This is shown for aptamers binding thrombin or ATP. Binding of aptamers results in quenching of fluorescence. If thrombin or ATP are introduced, the respective aptamer will bind them, and the complex is then released from the PEI-CDs. Fluorescence increases in proportion to the analyte concentration. Under optimized conditions, thrombin and ATP can be sensitively and selectively detected by fluorometry with lower detection limits of 1.2 and 13 nM, respectively. The assay was successfully applied to the determination of thrombin and of ATP in spiked serum samples. Graphical abstract Green fluorescent carbon quantum dots were functionalized with polyethyleneimine. They were applied to aptamer-based determination of thrombin and ATP. The PEI-functionalized carbon quantum dots (PEI-CDs) have bright green fluorescence are were synthesized by one-step hydrothermal treatment of malic acid and PEI. Employing the PEI-CDs, a fluorometric aptamer-based assay was developed for the determination of thrombin and ATP.

Process optimization and kinetic analysis of malic acid production from crude glycerol using Aspergillus niger

In the present work, optimization of crude glycerol fermentation to produce malic acid by using Aspergillus niger was investigated using response surface methodology and artificial neural network. Kinetic investigation of bioconversion of crude glycerol into malic acid using Aspergillus niger was studied using Monod, Mosser, and Haldane-Andrew models. Crude glycerol concentration, initial pH and yeast extract concentration were found to be significant compounds affecting malic acid production by Aspergillus niger. Both dry cell weight and malic acid titre were found decreased with increase in crude glycerol concentration. Haldane-Andrew model gave the best fit for the production of malic acid from crude glycerol with µ_max of 0.1542 h^-1. The maximum malic acid production obtained under optimum conditions was 92.64 + 1.54 g/L after 192 h from crude glycerol using Aspergillus niger.

Development of apple wine from Golden Delicious cultivar using a local yeast isolate

The present study was conducted to optimize fermentation parameters for apple wine production using Golden Delicious apples. Physicochemical analysis of the cultivar revealed a °Brix-acid ratio of 24.61 with ample amount of total and reducing sugars (9.6 and 6.03% w/v); making it a suitable substrate to produce ethanol. Microbiological analysis lead to isolation of a yeast strain (namely A2) which was molecularly identified and accessed at GenBank as S. cerevisiae KY069279. Ethanol fermentation optimization using response surface methodology revealed that a temperature of 20 °C, an inoculum size of 7.08 (%v/v) and diammonium hydrogen phosphate supplementation @ 154.4 mg/100 mL as optimum for apple wine production which lead to 10.73% (v/v) ethanol production with a desirability of 86.9%. Fresh wine having malic acid content of 1.87 (mg/100 mL) was subjected to malolactic fermentation (MLF) for 8 days using Leuconostoc oenos NCIM 2219 resulting in apple wine having 0.4 (mg/100 mL) malic acid. Sensory analysis of MLF and non-MLF apple wines categorised them as superior quality with average scores of 69.5 and 74.5, respectively. Gas chromatography-mass spectrometric analysis of apple wine revealed the presence of 38 volatile compounds including higher alcohols, acids, esters etc. The study thus revealed a process for apple wine preparation using an indigenous yeast and also optimized and compared malolactic and non-malolactic fermented ciders.

Discovery and mechanism study of a novel chromium-accumulating plant, Lonicera japonica Thunb

Finding chromium-accumulating plants is of great interest for phytoremediation of soil contaminated by chromium (Cr). Inspired by Traditional Chinese Medicine, we examined the Cr-resistance and Cr-accumulation of Lonicera japonica Thunb. After a two-phase study using both soil and water culture, we found that L. japonica could be a novel Cr-accumulating plant, which contains an average Cr(III) content of 1297.14 mg^.kg^-1 in its leaves. The Cr enrichment factor and the Cr transport coefficient of Lonicera japonica was 5.19 and 1.79, respectively. Lonicera japonica is the fifth Cr-accumulating plant discovered worldwide, and the first Cr-accumulating woody plant ever discovered. The results support the conclusions drawn from studies of Cr-accumulating Leersia hexandra that oxalic acid production can increase Cr tolerance whereas citric acid or malic acid has no effect, suggesting that oxalic acid might be a common reason for Cr tolerance in all Cr-accumulating plants. Moreover, this study revealed that the production of anthocyanin and carotene can also increase Cr(III) tolerance, suggesting that anthocyanin and carotene might also account for Cr tolerance in Cr-accumulating plants. We believe that the discovery of Lonicera japonica as a Cr-accumulating plant will offer great opportunities in phytoremediation, and the success should be a strong sign that Traditional Chinese Medicine harbors more secrets to be uncovered with modern science.

The impacts of Schizosaccharomyces on winemaking

In the past century, yeasts from the genus Saccharomyces represented the only option in fermentation industries, such as winemaking, to produce wine, beer, and other fermented products. However, other genera are currently emerging to solve challenges in modern enology. Schizosaccharomyces pombe is showing promising results in solving specific challenges in northern, cool viticulture regions with highly acidic wines by deacidifying these wines through its malic acid metabolism. In addition, this microorganism is considered beneficial in warm growing regions with challenges such as the control of wine food safety problems such as the presence of biogenic amines, ochratoxin A, or ethyl carbamate. Indeed, the genus Schizosaccharomyces positively influences other important wine quality parameters, such as color and polysaccharide content. However, the main challenge of using this genus remains the selection of proper strains that alleviate problems such as the production of high acetate concentrations. Industries other than wine production such as ginger fermentation, apple wine, Kei-apple fermentation, plum wine, sparkling wine, and bilberry fermentation industries have also started to study Schizosaccharomyces species as an alternative tool for solving specific related problems. The review discusses the influence of Schizosaccharomyces on different fermentation quality parameters and its main applications in different industries.

First ethnobotanical inventory and phytochemical analysis of plant species used by indigenous people living in the Maromizaha forest, Madagascar

ETHNOPHARMACOLOGICAL RELEVANCE

Characterized by one of the highest rates of endemism and biodiversity in the world, Madagascar provides a wide variety of medicinal plants, that could represent a potential source of new drugs. The main aim of this study was to investigate the potential medicinal properties of the plant species used by indigenous people in Maromizaha forest and to provide the first ethnobotanical inventory of the area.

MATERIALS AND METHODS

Data were collected through open semi-structured interviews with local informants, the reported plants were collected and identified to create a specimen herbarium. Informant Consensus Factor (ICF) was calculated for each ailment category mentioned in the use-reports. A selection of seven medicinal plants was submitted to phytochemical and antimicrobial analysis. The results were discussed and compared with those described in ethnobotanical and pharmacological literature.

RESULTS

One hundred and three villagers were interviewed and a total of 509 use-reports were recorded. Information on 117 plant species belonging to 57 botanical families were provided. 12 categories of indigenous uses were recognized, among them the higher ICF values were recorded for cardiovascular complaints (0.75), general and unspecific diseases (0.74), digestive disorders (0.69), and diseases of the skin (0.55). The traditional medicinal uses of 18 species (15 endemic) were described for the first time. In total, 22 different bioactive compounds were identified; polyphenols, monoterpenes, organic acids, and vitamin C were observed in the chemical composition of all the analyzed samples. Macaranga perrieri showed the highest values of both total polyphenolic compounds and antioxidant activity. Antimicrobial activity was observed in leaf and bark extracts of Dilobeia thouarsii.

CONCLUSION

These results confirmed the importance of investigating the traditional use of plant species, suggesting the crucial role of ethnobotanical studies for rural development, biodiversity conservation, and the sustainable use of plant resources in the studied area.

Malic acid production from biodiesel derived crude glycerol using morphologically controlled Aspergillus niger in batch fermentation

In the present investigation, the effects of crude glycerol concentration, spore inoculum concentration, yeast extract concentration and shaking frequency on seed morphology of Aspergillus niger PJR1 on malic acid production were investigated and dispersed fungal mycelium with higher biomass (20.25 ± 0.91 g/L) was obtained when A. niger PJR1 grow on crude glycerol. Dry cell weight under dispersed fermentation was 21.28% higher than usual pellet fermentation. The optimal crude glycerol, nitrogen source and nitrogen source concentration were found to be 160 g/L, yeast extract and 1.5 g/L, respectively. Batch fermentation in a shake flask culture containing 160 g/L crude glycerol resulted in the yield of malic acid 83.23 ± 1.86 g/L, after 192 h at 25 °C. Results revealed that morphological control of A. niger is an efficient method for increased malic acid production when crude glycerol derived from biodiesel production is used as feedstock.

Genetic manipulation of Escherichia coli central carbon metabolism for efficient production of fumaric acid

Fumaric acid is one of the top 12-biomass building-block chemicals. In this study, we reported manipulation of E. coli central carbon metabolism with the aim to decrease the by-products and improve fumaric acid production. PEP-dependent glucose phosphotransferase system was replaced with a galactose translocation system to minimize the consumption of phosphoenolpyruvate. Engineering anaplerotic pathway (phosphoenolpyruvate carboxylase) was employed to redistribute carbon flux from glycolysis to Krebs cycle. Deletion of malate dehydrogenase and overexpression of acetyl-CoA synthase could decrease the byproducts malic acid and acetic acid. The combined strategies led to fumaric acid yield up to 1.53 g/g dry cell weight, a 50% increase compared with the parental strain. The result demonstrated that these genetic modifications were effective strategies for improving the production of fumaric acid and the engineered strain may serve a platform microbial cell factory for efficient production of fumaric acid or other dicarboxylic acids.

Sustainable green pretreatment approach to biomass-to-energy conversion using natural hydro-low-transition-temperature mixtures

Natural hydro-low-transition-temperature mixtures (NH-LTTMs) tend to be the most favorable next-generation green solvents for biomass pretreatment, as they are cheap and environmental friendly. The amount of water bound into the NH-LTTMs greatly affected their thermal stability, whereby the highest thermal stability was observed with the water content of 7.6 wt%. It is worth noting that, the highest molar transition energy of NH-LTTMs (47.57 kcal mol^-1), which indicated the highest solubility, was optimized with the molar ratio of hydrogen bond donor (HBD)-hydrogen bond acceptor (HBA)-water (2:4:3) at a temperature of 60 °C. Hydrogen bonding networks of the NH-LTTMs, which led to the dissolution of biomass, were confirmed by the alteration in the peaks of the involved bonds and resonance signal to lower field through FTIR and ¹H NMR spectra, respectively. The components evidenced in high-resolution mass spectra of extracted lignin showed its high potential to be valorized into useful fuels and chemicals.

Engineering of Escherichia coli for Krebs cycle-dependent production of malic acid

Background

Malate is a C4-dicarboxylic acid widely used as an acidulant in the food and beverage industry. Rational engineering has been performed in the past for the development of microbial strains capable of efficient production of this metabolite. However, as malate can be a precursor for specialty chemicals, such as 2,4-dihydroxybutyric acid, that require additional cofactors NADP(H) and ATP, we set out to reengineer Escherichia coli for Krebs cycle-dependent production of malic acid that can satisfy these requirements.

Results

We found that significant malate production required at least simultaneous deletion of all malic enzymes and dehydrogenases, and concomitant expression of a malate-insensitive PEP carboxylase. Metabolic flux analysis using ¹³C-labeled glucose indicated that malate-producing strains had a very high flux over the glyoxylate shunt with almost no flux passing through the isocitrate dehydrogenase reaction. The highest malate yield of 0.82 mol/mol was obtained with E. coli Δmdh Δmqo ΔmaeAB ΔiclR ΔarcA which expressed malate-insensitive PEP carboxylase Ppc^K620S and NADH-insensitive citrate synthase GltA^R164L. We also showed that inactivation of the dicarboxylic acid transporter DcuA strongly reduced malate production arguing for a pivotal role of this permease in malate export.

Conclusions

Since more NAD(P)H and ATP cofactors are generated in the Krebs cycle-dependent malate production when compared to pathways which depend on the function of anaplerotic PEP carboxylase or PEP carboxykinase enzymes, the engineered strain developed in this study can serve as a platform to increase biosynthesis of malate-derived metabolites such as 2,4-dihydroxybutyric acid.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-0959-y) contains supplementary material, which is available to authorized users.

A novel malic acid-enhanced method for the analysis of 5-methyl-2'-deoxycytidine, 5-hydroxymethyl-2'-deoxycytidine, 5-methylcytidine and 5-hydroxymethylcytidine in human urine using hydrophilic interaction liquid chromatography-tandem mass spectrometry

5-Methyl-2'-deoxycytidine (5-mdC), 5-hydroxymethyl-2'-deoxycytidine (5-hmdC), 5-methylcytidine (5-mrC) and 5-hydroxymethylcytidine (5-hmrC) are epigenetic marks of DNA and RNA, and aberrant levels of these modified nucleosides were found to be associated with various cancers. Urine is a preferred source of biological fluid for biomarker discovery because the sample collection process is not invasive to patients. Herein, we developed a novel malic acid-enhanced hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) method for sensitive and simultaneous quantification of the modified cytosine nucleosides in human urine. Malic acid markedly increased the detection sensitivities of all four cytosine nucleosides, with the limits of detection (LODs) for 5-mdC, 5-hmdC, 5-mrC and 5-hmrC being 0.025, 0.025, 0.025 and 0.050 fmol, respectively. By using this method, we demonstrated, for the first time, the presence of 5-hmrC in human urine, and we successfully quantified 5-mdC, 5-hmdC, 5-mrC and 5-hmrC in urine samples collected from 90 patients with colorectal cancer (CRC) and 90 healthy controls. We found that the levels of 5-mdC, 5-hmdC, 5-mrC and 5-hmrC in urine were all substantially decreased in CRC patients, suggesting that these modified nucleosides might have great potential to be noninvasive biomarkers for early detection and prognosis of CRC. Together, we established a novel and sensitive method for detecting 5-methylated and 5-hydroxymethylated cytosine nucleosides in human urine and the results from this study may stimulate future investigations about the regulatory roles of these cytosine derivatives in the initiation and development of CRC.

Quantification of sugars and organic acids in tomato fruits

Sugar and organic acid contents are major factors for tomato fruit flavour and are important breeding traits. Here we provide an improved protocol for accurate quantification of the main sugars, glucose and fructose, and the organic acids, citric acid and malic acid, present in tomato. The tomato extract is spiked with lactose and tricarballylic acid as internal standards and loaded onto a NH2 solid phase extraction (SPE) column. The sugars appear in the flow-through and are subsequently analysed by HPLC using a Nucleodur NH2 column and a refractive index detector. The organic acids bind to the SPE column and are eluted with 400 mM phosphoric acid. For analysis, the organic acids are separated by HPLC using a Nucleodur C18ec column and detected by UV absorption at 210 nm. The method shows excellent inter-day and intra-day reproducibility for glucose, fructose and citric acid with standard deviations of 1–5%. Quantification of citric acid by HPLC and GC–MS showed perfect agreement with a deviation of less than 3%.

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Simple method for quantification of glucose, fructose, citric acid and malic acid in tomato.

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Efficient removal of interfering compounds by solid phase extraction.

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High intra and inter-day reproducibility.

Nutritional characterization of apple as a function of genotype

Twenty two apple cultivars grown in Himachal Pradesh, India were harvested at commercial maturity and analysed for different physical (fruit weight, fruit dimensions, firmness, color) and nutritional attributes (ascorbic acid, antioxidant activity, total carotenoid, sugars, organic acids, phenolic compounds and minerals). Cultivar 'Oregon Spur II' was found to have maximum fruit size and weight while the least was observed for cultivar 'Starkrimson'. Quantitative differences were found in the nutritional profile among the cultivars with respect to all the above attributes. The ascorbic acid content ranged between 19.38 mg 100 g^-1 ('Well Spur') and 32.08 mg 100 g^-1 ('Starkrimson') while the antioxidant activity varied between 2.64 μmol Trolox equivalent g^-1 ('Granny Smith') and 13.20 μmol Trolox equivalent g^-1 ('Silver Spur'). The highest total carotenoid was found in 'Red Chief' (147.06 mg kg^-1) while in 'Early Red-I' the total carotenoid was only 29.03 mg kg^-1. HPLC analysis for individual sugars, organic acids and phenolic compounds was carried out. Fructose (average 50.79 g L^-1) was the most abundant sugar. Malic acid (average 6.03 mg L^-1) predominated among the individual organic acids. Potassium (average 795.14 mg 100 g^-1) and iron (average 2.04 µg g^-1) were the predominant macro and micro elements, respectively. Chlorogenic acid was the major constituent among phenolic compounds.

Malic acid production by chemically induced Aspergillus niger MTCC 281 mutant from crude glycerol

In the present investigation, crude glycerol derived from transesterification process was utilized to produce the commercially-valuable malic acid. A combined resistant on methanol and malic acid strain of Aspergillus niger MTCC 281 mutant was generated in solid medium containing methanol (1-5%) and malic acid (40-80 g/L) by the adaptation process for 22 weeks. The ability of induced Aspergillus niger MTCC 281 mutant to utilize crude glycerol and pure glycerol to produce malic acid was studied. The yield of malic acid was increased with 4.45 folds compared with that of parent strain from crude glycerol. The highest concentration of malic acid from crude glycerol by using beneficial mutant was found to be 77.38 ± 0.51 g/L after 192 h at 25 °C. This present study specified that crude glycerol by-product from biodiesel production could be used for producing high amount of malic acid without any pretreatment.

The contribution of weak CAM to the photosynthetic metabolic activities of a bromeliad species under water deficit

The Crassulacean acid metabolism (CAM) can be a transitory strategy for saving water during unfavourable conditions, like a dry season. In some cases, CAM can also contribute to the maintenance of photosynthetic integrity, even if carbon gain and growth are impaired. CAM occurs in different intensities, being stronger or weaker depending on the degree of nocturnal malic acid accumulation. For example, Guzmania monostachia is an epiphytic tank bromeliad that shows an increase in its nocturnal organic acid accumulation and a variable CAM behaviour when exposed to water deficit. In this context, this study aimed at investigating whether the weak CAM displayed by this species may mitigate the harmful effects of water limitation on its photosynthetic activity. To this, bromeliads were submitted to well-watered and water deficit conditions. Guzmania monostachia plants under water deficiency conditions showed a reduction on atmospheric carbon assimilation without exhibiting changes in PSII integrity and carbohydrate production while showed an increase in nocturnal malic acid accumulation. Additionally, spots with high PSII efficiency in the leaf portion with a greater nocturnal malic acid accumulation were observed in plants exposed to water shortage conditions. These high-efficiency spots might be associated with a greater malate decarboxylation capacity. Also, the malic acid contributed to approximately 50% of the total carbon assimilated under water deficit. These results suggest that weak CAM may participate in photo-protection and it appears to meaningfully contribute to the overall carbon balance, being an important metabolic strategy to maintain plant fitness during water deficit periods.

Schizosaccharomyces pombe Biotechnological Applications in Winemaking

The traditional way of producing wine is through the use of Saccharomyces cerevisiae in order to convert glucose and fructose into alcohol. In the case of red wines, after this alcoholic fermentation lactic bacteria Oenococus oeni is used to stabilize wine from a microbiological point of view by converting malic acid into lactic acid that it is not a microbiological substract. The yeast species Schizosaccharomyces pombe was traditionally considered spoilage yeast. Nevertheless, during the last decade it started to be used due to its unique malic acid deacidification ability to reduce the harsh acidity of wines from northern Europe, by converting malic acid to ethanol and CO₂ without producing lactic acid as lactic bacteria does. Additionally, during the last years, S. pombe has started to be used to solve the problems of modern winemaking industry such as increasing food quality or food safety. Some of those new uses, different from its traditional malic acid deacidification, are: high autolytic polysaccharides release, gluconic acid reduction, urease activity that make impossible ethyl carbamate (toxic compound) formation, high pyruvic acid production, that is related to color improvement, and removing lactic bacteria subtracts while avoiding biogenic amines (toxic compounds such as histamine) formation.

Schizosaccharomyces pombe Isolation Protocol

This chapter describes a methodology to isolate yeast strains from Schizosaccharomyces pombe species. The method is based on a selective-differential medium that notably facilitates the isolation of S. pombe. The main difficulty in isolating microorganisms from this genus is their extremely low incidence in nature when they are compared to other microorganisms. The proposed methodology allows isolating and selecting strains from this species for industrial purposes. Methodologies allows detecting the presence of those yeasts when they are considered spoilage microorganisms. Several selective-differential agents based on the basic physiological characteristics of S. pombe species are exposed during the chapter introduction and the use is properly justified. Some of those representative characteristics are its extraordinary resistance to high sugar concentrations, sulfur dioxide, sorbic acid, benzoic acid, acetic acid, or their unique malo-ethanolic fermentation ability. The proposed selective medium is mainly based on S. pombe resistance to the antibiotic actidione and the unusual tolerance to the inhibitory agent benzoic acid compared to possible microorganisms that could produce false-positive results during an isolation process. In addition, malic acid is proposed as the main differential factor due to the exclusive ability of this species to metabolize malic acid into ethanol. This fact allows the detection of malic acid degradation. Cloramphenicol is used to inhibit bacteria growth and liquid media to avoid fungi development.

Changes in the volatile profile of Pinot noir wines caused by Patagonian Lactobacillus plantarum and Oenococcus oeni strains

The ability of Patagonian L. plantarum and O. oeni strains to change the volatile profile of a sterile Pinot noir wine was studied through fermentation assays, at laboratory scale. Two strains of each LAB species were selected based on data regarding to their ability to survive in wine and to consume l-malic acid. Both O. oeni strains but only one L. plantarum (UNQLp 11) strain were able to remain viable, consuming l-malic acid through the fermentation assay with a concomitant increase of l-lactic acid. The volatile profile of Pinot noir wine, before and after LAB inoculation, was measured by using HS-SPME gas chromatography technique. This analysis showed that alcohols were the main volatile compounds after alcoholic fermentation and that after fermentation with the selected LAB strains, a decrease in the volatile alcohols concentration and an increase in the volatile esters concentration could be observed. The O. oeni UNQOe 73.2 strain produced the most notable change in the volatile profile, with the production of some important odorant esters at higher concentration, compared to O. oeni UNQOe 31b strain. Although, L. plantarum UNQLp 11 strain showed a better performance in the consumption of l-malic acid, this strain had a low capacity to modify the volatile compounds profile after incubation in red wine. The results found in the present work showed that different strains selected as potential malolactic starters could have different behavior when are incubated in real wine. Although L. plantarum UNQLp 11 strain showed a good consumption of l-malic acid, the O. oeni UNQOe 73.2 strain exhibited superior capacity to improve the flavor of wine due to its esterase activity that produce an increase of fruity and creamy odorants.

Choline chloride (ChCl) and monosodium glutamate (MSG)-based green solvents from optimized cactus malic acid for biomass delignification

This work aimed to develop an efficient microwave-hydrothermal (MH) extraction of malic acid from abundant natural cactus as hydrogen bond donor (HBD) whereby the concentration was optimized using response surface methodology. The ideal process conditions were found to be at a solvent-to-feed ratio of 0.008, 120°C and 20min with 1.0g of oxidant, H₂O₂. Next generation environment-friendly solvents, low transition temperature mixtures (LTTMs) were synthesized from cactus malic acid with choline chloride (ChCl) and monosodium glutamate (MSG) as hydrogen bond acceptors (HBAs). The hydrogen-bonding interactions between the starting materials were determined. The efficiency of the LTTMs in removing lignin from oil palm biomass residues, empty fruit bunch (EFB) was also evaluated. The removal of amorphous hemicellulose and lignin after the pretreatment process resulted in an enhanced digestibility and thermal degradability of biomass.

Sustainable carbon sources for microbial organic acid production with filamentous fungi

BACKGROUND

The organic acid producer Aspergillus oryzae and Rhizopus delemar are able to convert several alternative carbon sources to malic and fumaric acid. Thus, carbohydrate hydrolysates from lignocellulose separation are likely suitable as substrate for organic acid production with these fungi.

RESULTS

Before lignocellulose hydrolysate fractions were tested as substrates, experiments with several mono- and disaccharides, possibly present in pretreated biomass, were conducted for their suitability for malic acid production with A. oryzae. This includes levoglucosan, glucose, galactose, mannose, arabinose, xylose, ribose, and cellobiose as well as cheap and easy available sugars, e.g., fructose and maltose. A. oryzae is able to convert every sugar investigated to malate, albeit with different yields. Based on the promising results from the pure sugar conversion experiments, fractions of the organosolv process from beechwood (Fagus sylvatica) and Miscanthus giganteus were further analyzed as carbon source for cultivation and fermentation with A. oryzae for malic acid and R. delemar for fumaric acid production. The highest malic acid concentration of 37.9 ± 2.6 g/L could be reached using beechwood cellulose fraction as carbon source in bioreactor fermentation with A. oryzae and 16.2 ± 0.2 g/L fumaric acid with R. delemar.

CONCLUSIONS

We showed in this study that the range of convertible sugars for A. oryzae is even higher than known before. We approved the suitability of fiber/cellulose hydrolysate obtained from the organosolv process as carbon source for A. oryzae in shake flasks as well as in a small-scale bioreactor. The more challenging hemicellulose fraction of F. sylvatica was also positively evaluated for malic acid production with A. oryzae.

Exogenous malic acid alleviates cadmium toxicity in Miscanthus sacchariflorus through enhancing photosynthetic capacity and restraining ROS accumulation

Malic acid (MA) plays an important role in the regulation of plant growth, stomatal aperture, nutrition elements homeostasis and toxic metals tolerance. However, little is known about the effects of exogenous MA on physiological and biochemical responses to toxic metals in plants. To measure the alleviation roles of exogenous MA against cadmium (Cd), we determined the effects of MA on plant growth, net photosynthetic rate (Pn), reactive oxygen species (ROS) accumulation and the activities of anti-oxidant enzymes in the leaves of Miscanthus sacchariflorus (M. sacchariflorus) under Cd stress. The Cd exposure alone significantly inhibited plant growth and Pn, but increased the accumulation of ROS even though the anti-oxidant enzymes were markedly activated in the leaves of M. sacchariflorus. Treatment with MA significantly enhanced plant growth and decreased Cd accumulation accompanied by increasing Pn under Cd stress as compared to Cd stress alone, especially when treatment with high concentration of MA (200μM) was used. In addition, Cd and MA indicated synergistic effects by further increasing the activities and genes expression of partial anti-oxidant enzymes, thus resulting in higher glutathione accumulation and reduction of ROS production. The results showed that application of MA alleviated Cd-induced phytotoxicity and oxidant damage through the regulation of both enzymatic and non-enzymatic anti-oxidants under Cd stress in M. sacchariflorus.

Overexpression of a C4-dicarboxylate transporter is the key for rerouting citric acid to C4-dicarboxylic acid production in Aspergillus carbonarius

Background

C₄-dicarboxylic acids, including malic acid, fumaric acid and succinic acid, are valuable organic acids that can be produced and secreted by a number of microorganisms. Previous studies on organic acid production by Aspergillus carbonarius, which is capable of producing high amounts of citric acid from varieties carbon sources, have revealed its potential as a fungal cell factory. Earlier attempts to reroute citric acid production into C₄-dicarboxylic acids have been with limited success.

Results

In this study, a glucose oxidase deficient strain of A. carbonarius was used as the parental strain to overexpress a native C₄-dicarboxylate transporter and the gene frd encoding fumarate reductase from Trypanosoma brucei individually and in combination. Impacts of the introduced genetic modifications on organic acid production were investigated in a defined medium and in a hydrolysate of wheat straw containing high concentrations of glucose and xylose. In the defined medium, overexpression of the C₄-dicarboxylate transporter alone and in combination with the frd gene significantly increased the production of C₄-dicarboxylic acids and reduced the accumulation of citric acid, whereas expression of the frd gene alone did not result in any significant change of organic acid production profile. In the wheat straw hydrolysate after 9 days of cultivation, similar results were obtained as in the defined medium. High amounts of malic acid and succinic acid were produced by the same strains.

Conclusions

This study demonstrates that the key to change the citric acid production into production of C₄-dicarboxylic acids in A. carbonarius is the C₄-dicarboxylate transporter. Furthermore it shows that the C₄-dicarboxylic acid production by A. carbonarius can be further increased via metabolic engineering and also shows the potential of A. carbonarius to utilize lignocellulosic biomass as substrates for C₄-dicarboxylic acid production.

Polymalic acid fermentation by Aureobasidium pullulans for malic acid production from soybean hull and soy molasses: Fermentation kinetics and economic analysis

Polymalic acid (PMA) production by Aureobasidium pullulans ZX-10 from soybean hull hydrolysate supplemented with corn steep liquor (CSL) gave a malic acid yield of ∼0.4g/g at a productivity of ∼0.5g/L·h. ZX-10 can also ferment soy molasses, converting all carbohydrates including the raffinose family oligosaccharides to PMA, giving a high titer (71.9g/L) and yield (0.69g/g) at a productivity of 0.29g/L·h in fed-batch fermentation under nitrogen limitation. A higher productivity of 0.64g/L·h was obtained in repeated batch fermentation with cell recycle and CSL supplementation. Cost analysis for a 5000 MT plant shows that malic acid can be produced at $1.10/kg from soy molasses, $1.37/kg from corn, and $1.74/kg from soybean hull. At the market price of $1.75/kg, malic acid production from soy molasses via PMA fermentation offers an economically competitive process for industrial production of bio-based malic acid.