Concentration dependent cholesteryl-ester and wax-ester structural relationships and meibomian gland dysfunction

BackgroundWith dry eye, the ratio of cholesteryl ester (CE) to wax ester (WE) decreases substantially in meibum, but the functional and structural consequences of this change are speculative. The aim of this study is to confirm this finding and to bridge this gap in knowledge by investigating the effect of varying CE/WE ratios on lipid structure and thermodynamics.MethodsInfrared spectroscopy was use to quantify CE and WE in human meibum and to measure hydrocarbon chain conformation and thermodynamics in a cholesteryl behenate, stearyl stearate model system.ResultsThe CE/WE molar ratio was 36% lower for meibum from donors with dry eye due to meibomian gland dysfunction compared with meibum from donors without dry eye. CE (5 mol %) dramatically increased the phase transition temperature of pure WE from -0.12 °C to 63 °C in the mixture. Above 5 mol % CB, the phase transition temperature increased linearly, from 68.5 °C to 85 °C. In the ordered state, CE caused an increase in lipid order from about 72% trans rotamers to about 86% trans rotamers. Above 10% CE, the hydrocarbon chains were arranged in a monoclinic geometry.ConclusionsThe CE/WE is lower in meibum from donors with dry eye due to meibomian-gland dysfunction. Major conformational changes in the hydrocarbon chains of wax and cholesteryl ester mixtures begin to occur with just 5% CB and above.General significanceCE-WE interactions may be important for in understanding lipid layer structure and functional relationships on the surface of tears, skin and plants.     

Engineering Yarrowia lipolytica for the selective and high-level production of isocitric acid through manipulation of mitochondrial dicarboxylate–tricarboxylate carriers

During cultivation under nitrogen starvation, Yarrowia lipolytica produces a mixture of citric acid and isocitric acid whose ratio is mainly determined by the carbon source used. We report that mitochondrial succinate–fumarate carrier YlSfc1 controls isocitric acid efflux from mitochondria. YlSfc1 purified and reconstituted into liposomes transports succinate, fumarate, oxaloacetate, isocitrate and α-ketoglutarate. YlSFC1 overexpression determined the inversion of isocitric acid/citric acid ratio towards isocitric acid, resulting in 33.4 ± 1.9 g/L and 43.3 ± 2.8 g/L of ICA production in test-tube cultivation with glucose and glycerol, respectively. These titers represent a 4.0 and 6.3-fold increase compared to the wild type. YlSFC1 gene expression was repressed in the wild type strain grown in glucose-based medium compared to olive oil medium explaining the reason for the preferred citric acid production during Y. lipolytica growth on carbohydrates. Coexpression of YlSFC1 and adenosine monophosphate deaminase YlAMPD genes together with inactivation of citrate mitochondrial carrier YlYHM2 gene enhanced isocitric acid accumulation up to 41.4 ± 4.1 g/L with an isocitric acid/citric acid ratio of 14.3 in a small-scale cultivation with glucose as a carbon source. During large-scale cultivation with glucose pulse-feeding, the engineered strain produced 136.7 ± 2.5 g/L of ICA with a process selectivity of 88.1%, the highest reported titer and selectivity to date. These results represent the first reported isocitric acid secretion by Y. lipolytica as a main organic acid during cultivation on carbohydrate. Moreover, we demonstrate for the first time that the replacement of one mitochondrial transport system for another can be an efficient tool for switching product accumulation.     

Pomegranate peels waste hydrolyzate optimization by Response Surface Methodology for Bioethanol production

Unwanted agricultural waste is largely comprised of lignocellulosic substrate which could be transformed into sugars. The production of bioethanol from garbage manifested an agreeable proposal towards waste management as well as energy causation. The goal of this work is to optimize parameters for generation of bioethanol through fermentation by different yeast strains while Saccharomyces cerevisiae used as standard strain. The low cost fermentable sugars from pomegranate peels waste (PPW) were obtained by hydrolysis with HNO₃ (1 to 5%). The optimum levels of hydrolysis time and temperature were elucidated via RSM (CCD) ranging from 30 to 60 min and 50 to 100 °C respectively. The result shows that optimum values (g/L) for reducing sugars was 61.45 ± 0.01 while for total carbohydrates was 236 ± 0.01. These values were found when PPW was hydrolyzed with 3% HNO₃, at 75 °C for one hour. The hydrolyzates obtained from the dilute HNO₃ pretreated PPW yielded a maximum of 0.43 ± 0.04, 0.41 ± 0.03 g ethanol per g of reducing sugars by both Metchnikowia sp. Y31 and M. cibodasensis Y34 at day 7 of ethanologenic experiment. The current study exhibited that by fermentation of dilute HNO₃ hydrolyzates of PPW could develop copious amount of ethanol by optimized conditions.     

Xanthone C-glycosides isomers purified from Dryopteris ramosa (Hope) C. Chr. with bactericidal and cytotoxic prospects

Xanthones C-glycosides are plants secondary metabolites with diverse biological activities. Among the C-glycoside xanthones, the mangiferin (MF) is of widespread occurrence in plants while isomangiferin (IsoMF) is not very common. For the present study mangiferin (MF) and isomangiferin (IsoMF) were isolated from Dryopteris ramosa. The antibacterial potential of MF and IsoMF was evaluated by using agar well diffusion method while cytotoxic properties of MF and IsoMF were assessed by brine shrimp lethality test (BSLT). The antibacterial potential of MF and IsoMF increases in dose dependent manner. The minimum inhibitory concentration (MIC) indicated strong antibacterial potential of MF against Salmonella setubal (125 µg/mL) and Bacillus subtilis (125 µg/mL) while MF showed weak antibacterial potential against Escherichia coli (500 µg/mL). On the other hand the IsoMF showed better antibacterial potential against all the tested strain including Escherichia coli (MIC = 250 µg/mL). The MF and IsoMF showed poor cytotoxicity towards Brine shrimp nauplii as indicated by their LD₅₀ (969.77 ± 0.67 and 768.92 ± 0.81 µg/mL respectively). The present study has highlighted the antibacterial potential of MF and IsoMF. Further evaluation of these two isomeric compounds may prove to be the future remedies for various bacterial infections and other human ailments.     

Reprogramming Escherichia coli pyruvate-forming reaction towards chorismate derivatives production

Microbial metabolic pathway engineering is a potent strategy used worldwide to produce aromatic compounds. We drastically rewired the primary metabolic pathway of Escherichia coli to produce aromatics and their derivatives. The metabolic pathway of E. coli was compartmentalized into the production and energy modules. We focused on the pyruvate-forming reaction in the biosynthesis pathway of some compounds as the reaction connecting those modules. E. coli strains were engineered to show no growth unless pyruvate was synthesized along with the compounds of interest production. Production of salicylate and maleate was demonstrated to confirm our strategy's versatility. In maleate production, the production, yield against the theoretical yield, and production rate reached 12.0 g L⁻¹, 67%, and up to fourfold compared to that in previous reports, respectively; these are the highest values of maleate production in microbes to our knowledge. The results reveal that our strategy strongly promotes the production of aromatics and their derivatives.     

High titer methyl ketone production with tailored Pseudomonas taiwanensis VLB120

Methyl ketones present a group of highly reduced platform chemicals industrially produced from petroleum-derived hydrocarbons. They find applications in the fragrance, flavor, pharmacological, and agrochemical industries, and are further discussed as biodiesel blends. In recent years, intense research has been carried out to achieve sustainable production of these molecules by re-arranging the fatty acid metabolism of various microbes. One challenge in the development of a highly productive microbe is the high demand for reducing power. Here, we engineered Pseudomonas taiwanensis VLB120 for methyl ketone production as this microbe has been shown to sustain exceptionally high NAD(P)H regeneration rates. The implementation of published strategies resulted in 2.1 g L_aq⁻¹ methyl ketones in fed-batch fermentation. We further increased the production by eliminating competing reactions suggested by metabolic analyses. These efforts resulted in the production of 9.8 g L_aq⁻¹ methyl ketones (corresponding to 69.3 g L_org⁻¹ in the in situ extraction phase) at 53% of the maximum theoretical yield. This represents a 4-fold improvement in product titer compared to the initial production strain and the highest titer of recombinantly produced methyl ketones reported to date. Accordingly, this study underlines the high potential of P. taiwanensis VLB120 to produce methyl ketones and emphasizes model-driven metabolic engineering to rationalize and accelerate strain optimization efforts.     

Relationship between hepatic and mitochondrial ceramides: a novel in vivo method to track ceramide synthesis

Ceramides (CERs) are key intermediate sphingolipids implicated in contributing to mitochondrial dysfunction and the development of multiple metabolic conditions. Despite the growing evidence of CER role in disease risk, kinetic methods to measure CER turnover are lacking, particularly using in vivo models. The utility of orally administered ¹³C₃, ¹⁵N l-serine, dissolved in drinking water, was tested to quantify CER 18:1/16:0 synthesis in 10-week-old male and female C57Bl/6 mice. To generate isotopic labeling curves, animals consumed either a control diet or high-fat diet (HFD; n = 24/diet) for 2 weeks and varied in the duration of the consumption of serine-labeled water (0, 1, 2, 4, 7, or 12 days; n = 4 animals/day/diet). Unlabeled and labeled hepatic and mitochondrial CERs were quantified using liquid chromatography tandem MS. Total hepatic CER content did not differ between the two diet groups, whereas total mitochondrial CERs increased with HFD feeding (60%, P < 0.001). Within hepatic and mitochondrial pools, HFD induced greater saturated CER concentrations (P < 0.05) and significantly elevated absolute turnover of 16:0 mitochondrial CER (mitochondria: 59%, P < 0.001 vs. liver: 15%, P = 0.256). The data suggest cellular redistribution of CERs because of the HFD. These data demonstrate that a 2-week HFD alters the turnover and content of mitochondrial CERs. Given the growing data on CERs contributing to hepatic mitochondrial dysfunction and the progression of multiple metabolic diseases, this method may now be used to investigate how CER turnover is altered in these conditions.     

Genotypic and phenotypic characterization of industrial autochthonous Saccharomyces cerevisiae for the selection of well-adapted bioethanol-producing strains

In northwestern Argentina, sugarcane-derived industrial fermentation is being extensively used for bioethanol production, where highly adaptive native strains compete with the baker's yeast Saccharomyces cerevisiae traditionally used as starter culture. Yeast populations of 10 distilleries from Tucumán (Argentina) were genotypic and phenotypic characterized to select well-adapted bioethanol-producing autochthonous strains to be used as starter cultures for the industrial production of bioethanol fuel. From the 192 isolates, 69.8% were identified as S. cerevisiae, 25.5% as non-Saccharomyces, and 4.7% as Saccharomyces sp. wild yeasts. The majority of S. cerevisiae isolates (68.5%) were non-flocculating yeasts, while the flocculating strains were all obtained from the only continuous fermentation process included in the study. Simple Sequence Repeat analysis revealed a high genetic diversity among S. cerevisiae genotypes, where all of them were very different from the original baker's strain used as starter. Among these, 38 strains multi-tolerant to stress by ethanol (8%), temperature (42.5 °C) and pH (2.0) were obtained. No major differences were found among these strains in terms of ethanol production and residual sugars in batch fermentation experiments with cell recycling. However, only 10 autochthonous strains maintained their viability (more than 80%) throughout five consecutive cycles of sugarcane-based fermentations. In summary, 10 autochthonous isolates were found to be superior to baker's yeast used as starter culture (S. cerevisiae Calsa) in terms of optimal technological, physiological and ecological properties. The knowledge generated on the indigenous yeast populations in industrial fermentation processes of bioethanol-producing distilleries allowed the selection of well-adapted bioethanol-producing strains.     

Combined immobilized lipases for effective biodiesel production from spent coffee grounds

This work describes the enzymatic transesterification of the oil extracted from SCGs for synthesis of biodiesel as a promising alternative to diesel fuels based on petroleum. Biocatalysts from various sources were tested for biodiesel synthesis using coffee oil among which CaCO₃- immobilized Staphylococcus aureus and Bacillus stearothermophilus showed the highest conversion yields (61 ± 2.64% and 64.3 ± 1.53%, respectively) in 4 h. In further optimizing reaction parameters, methanol to oil molar ratio, biocatalyst quantity, water content, as well as incubation time and temperature markedly improved oil-to-biodiesel conversion up to 99.33 ± 0.57 % in a solvent free reaction after 12 h at 55 °C. A mixture of inexpensive CaCO₃-immobilized bacterial lipases at a 1:1 ratio was the best environment-friendly catalyst for biofuel synthesis as well as the ideal trade-off between conversion and cost. Obtained coffee biodiesel remained stable beyond 40 days at ambient storage conditions and its chemical characteristics were comparable to those of other known biodiesels according to the European requirements (EN14214). Collectively, SCGs, after oil extraction, could be an ideal substrate for the production of an environment-friendly biodiesel by using appropriate mixture of CaCO₃-immobilized lipases.     

Syntrophic co-culture of a methanotroph and heterotroph for the efficient conversion of methane to mevalonate

As the bioconversion of methane becomes increasingly important for bio-industrial and environmental applications, methanotrophs have received much attention for their ability to convert methane under ambient conditions. This includes the extensive reporting of methanotroph engineering for the conversion of methane to biochemicals. To further increase methane usability, we demonstrated a highly flexible and efficient modular approach based on a synthetic consortium of methanotrophs and heterotrophs mimicking the natural methane ecosystem to produce mevalonate (MVA) from methane. In the methane-conversion module, we used Methylococcus capsulatus Bath as a highly efficient methane biocatalyst and optimized the culture conditions for the production of high amounts of organic acids. In the MVA-synthesis module, we used Escherichia coli SBA01, an evolved strain with high organic acid tolerance and utilization ability, to convert organic acids to MVA. Using recombinant E. coli SBA01 possessing genes for the MVA pathway, 61 mg/L (0.4 mM) of MVA was successfully produced in 48 h without any addition of nutrients except methane. Our platform exhibited high stability and reproducibility with regard to cell growth and MVA production. We believe that this versatile system can be easily extended to many other value-added processes and has a variety of potential applications.     

Pseudomonas petrae sp. nov. isolated from regolith samples in Antarctica

A polyphasic taxonomic approach was used to characterize the four strains P2653^T, P2652, P2498, and P2647, isolated from Antarctic regolith samples. Initial genotype screening performed by PCR fingerprinting based on repetitive sequences showed that the isolates studied formed a coherent cluster separated from the other Pseudomonas species. Identification results based on 16S rRNA gene sequences showed the highest sequence similarity with Pseudomonas graminis (99.7%), which was confirmed by multilocus sequence analysis using the rpoB, rpoD, and gyrB genes. Genome sequence comparison of P2653^T with the most related P. graminis type strain DSM 11363^T revealed an average nucleotide identity of 92.1% and a digital DNA-DNA hybridization value of 46.6%. The major fatty acids for all Antarctic strains were C_16:0, Summed Feature 3 (C_16:1 ω7c/C_16:1 ω6c) and Summed Feature 8 (C_18:1 ω7c/C_18:1 ω6c). The predominant respiratory quinone was Q-9, and the major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, and phosphatidylglycerol. The regolith strains could be differentiated from related species by the absence of arginine dihydrolase, ornithine and lysine decarboxylase and by negative tyrosine hydrolysis. The results of this polyphasic study allowed the genotypic and phenotypic differentiation of four analysed strains from the closest related species, which confirmed that the strains represent a novel species within the genus Pseudomonas, for which the name Pseudomonas petrae sp. nov. is proposed with P2653^T (CCM 8850^T = DSM 112068^T = LMG 30619^T) as the type strain.     

Comparative study of the antioxidant activity of the essential oils of five plants against the H2O2 induced stress in Saccharomyces cerevisiae

The purpose of this work was to investigate the protective effect of five essential oils (EOs); Rosmarinus officinalis, Thymus vulgaris, Origanum compactum Benth., Eucalyptus globulus Labill. and Ocimum basilicum L.; against oxidative stress induced by hydrogen peroxide in Saccharomyces cerevisiae. The chemical composition of the EOs was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). The in vitro antioxidant activity was evaluated and the protective effect of EOs was investigated. Yeast cells were pretreated with different concentrations of EOs (6.25–25 µg/ml) for an hour then incubated with H₂O₂ (2 mM) for an additional hour. Cell viability, antioxidants (Catalase, Superoxide dismutase and Glutathione reductase) and metabolic (Succinate dehydrogenase) enzymes, as well as the level of lipid peroxidation (LPO) and protein carbonyl content (PCO) were evaluated. The chemical composition of EOs has shown the difference qualitatively and quantitatively. Indeed, O. compactum mainly contained Carvacrol, O. basilicum was mainly composed of Linalool, T. vulgaris was rich in thymol, R. officinalis had high α-Pinene amount and for E. globulus, eucalyptol was the major compound. The EOs of basil, oregano and thyme were found to possess the highest amount of total phenolic compounds. Moreover, they have shown the best protective effect on yeast cells against oxidative stress induced by H₂O₂. In addition, in a dose dependent manner of EOs in yeast medium, treated cells had lower levels of LPO, lower antioxidant and metabolic enzymes activity than cells exposed to H₂O₂ only. The cell viability was also improved. It seems that the studied EOs are efficient natural antioxidants, which can be exploited to protect against damages and serious diseases related to oxidative stress.     

Smilax china root extract as a novel Glucose- 6-phosphate dehydrogenase inhibitor for the treatment of hepatocellular carcinoma

A novel therapeutic strategy for cancer treatment is to target altered tumor metabolism. Glucose- 6-phosphate dehydrogenase (G6PD) has been recently discovered to be implicated in apoptosis and angiogenesis, making it an excellent target in cancer treatment. The current study aimed to screen the plant extracts library to find potent hits against G6PD through enzymatic assay. Protein expression was induced by IPTG and purified using Ni-NTA columns after transformation of the pET-24a-HmG6PD plasmid into E. coli BL21-DE3 strain. An enzymatic assay was established by using purified rG6PD protein, for the screening of G6PD inhibitors. Out of 46 plant extracts screened, the sixteen plant extracts have shown inhibitory activity against the G6PD enzyme. At doses from 1 to 4 µg/ml, this extract demonstrated concentration-dependent inhibition of G6PD with an IC₅₀ value of I.397 µg/ml. Moreover, the anticancer activity evaluation against HepG2 cells determined Smilax china as a potent inhibitor of cancer cells (IC₅₀ value of 16.017 μg/ml). The acute and subacute toxicities were not observed in mice with various concentrations (50, 100, 200 and 2000 mg/kg). Furthermore, to identify the compounds from Smilax china as G6PD inhibitors, a literature-based phytochemical investigation of Smilax china was conducted, and sixty compounds were docked against the NADP+ and G6P binding sites of G6PD. The results of this study showed that three compounds were Scirpusin A, Smilachinin and Daucosterol with MolDock Score of ?156.832, ?148.215, and ?145.733 respectively, against NADP+ binding site of G6PD. Conclusively, Smilax china root extract could be a safer drug candidate for the treatment of hepatocellular carcinoma.     

A new isoflavonol and other constituents from Cameroonian propolis and evaluation of their anti-inflammatory,antifungal and antioxidant potential

Propolis is rich in diverse bioactive compounds. Propolis samples were collected from three localities of Cameroon and used in the study. Column chromatography separation of propolis MeOH:DCM (50:50) extracts yielded a new isoflavonol, 2-hydroxy-8-prenylbiochanin A (1) alongside 2′,3′-dihydroxypropyltetraeicosanoate (2) and triacontyl p-coumarate (3) isolated from propolis for first time together with seven compounds: β-amyrine (4), oleanolic acid (5), β-amyrine acetate (6), lupeol (7), betulinic acid (8), lupeol acetate (9) and lupenone (10). These compounds were tested for their inhibitory effect on oxidative burst where intracellular reactive oxygen species (ROS) were produced from zymosan stimulated human whole blood phagocytes and on production of nitric oxide (NO) from lipopolysaccharide (LPS) stimulated J774.2 mouse macrophages. The cytotoxicity of these compounds was evaluated on NIH-3 T3 normal mouse fibroblast cells, antiradical potential on 2,2-diphenyl-1-picrylhydrazylhydrazyl (DPPH·) as well as their anti-yeast potential on four selected candida species. Compound 1 showed higher NO inhibition (IC₅₀ = 23.3 ± 0.3 µg/mL) than standard compound L-NMMA (IC₅₀ = 24.2 ± 0.8 µg/mL). Higher ROS inhibition was shown by compounds 6 (IC₅₀ = 4.3 ± 0.3 µg/mL) and 9 (IC₅₀ = 1.1 ± 0.1 µg/mL) than Ibuprofen (IC₅₀ = 11.2 ± 1.9 µg/mL). Furthermore, compound 1 displayed moderate level of cytotoxicity on NIH-3 T3 cells, with IC₅₀ = 5.8 ± 0.3 µg/mL compared to the cyclohexamide IC₅₀ = 0.13 ± 0.02 µg/mL. Compound 3 showed lower antifungal activity on Candida krusei and Candida glabrata, MIC of 125 μg/mL on each strain compared to 50 μg/mL for fuconazole. The extracts showed low antifungal activities ranging from 250 to 500 μg/mL on C. albicans, C. krusei and C. glabrata and the values of MIC on Candida parapsilosis were 500 μg/mL and above. DPPH* scavenging activity was exhibited by compounds 1 (IC₅₀ = 15.653 ± 0.335 μg/mL) and 3 (IC₅₀ = 89.077 ± 24.875 μg/mL) compared to Vitamin C (IC₅₀ = 3.343 ± 0.271 μg/mL) while extracts showed moderate antiradical activities with IC₅₀ values ranging from 309.31 ± 2.465 to 635.52 ± 11.05 µg/mL. These results indicate that compounds 1, 6 and 9 are potent anti-inflammatory drug candidates while 1 and 3 could be potent antioxidant drugs.     

Optimized plant compound with potent anti-biofilm activity across gram-negative species

Many human diseases, including cystic fibrosis lung infections, are caused or exacerbated by bacterial biofilms. Specialized modes of motility, including swarming and twitching, allow gram-negative bacteria to spread across surfaces and form biofilms. Compounds that inhibit these motilities could slow the spread of biofilms, thereby allowing antibiotics to work better. We previously demonstrated that a set of plant-derived triterpenes, including oleanolic acid and ursolic acid, inhibit formation of Escherichia coli and Pseudomonas aeruginosa biofilms, and alter expression of genes involved in chemotaxis and motility. In the present study, we have prepared a series of analogs of oleanolic acid. The analogs were evaluated against clinical isolates of E. coli and P. aeruginosa in biofilm formation assays and swarming assays. From these analogs, compound 9 was selected as a lead compound for further development. Compound 9 inhibits E. coli biofilm formation at 4 µg/mL; it also inhibits swarming at ≤1 µg/mL across multiple clinical isolates of P. aeruginosa, E. coli, Burkholderia cepacia, and Salmonella enterica, and at <0.5 µg/mL against multiple agricultural strains. Compound 9 also potentiates the activity of the antibiotics tobramycin and colistin against swarming P. aeruginosa; this is notable, as tobramycin and colistin are inhaled antibiotics commonly used to treat P. aeruginosa lung infections in people with cystic fibrosis. qPCR experiments suggested that 9 alters expression of genes involved in regulating Type IV pili; western blots confirmed that expression of Type IV pili components PilA and PilY1 decreases in P. aeruginosa in the presence of 9.     

Engineering cyanobacteria as cell factories for direct trehalose production from CO2

Trehalose is a non-reducing disaccharide with a wide range of applications in food, cosmetic, and pharmaceutical industries. Cyanobacteria are promising cell factories to produce biochemicals by using solar energy and CO₂. Trehalose is biosynthesized at low intracellular concentrations as a salt-inducible compatible solute in some cyanobacteria. In the current study, we demonstrated the efficient trehalose production without salt induction in cyanobacteria by metabolic engineering. The trehalose transporter 1 (TRET1) from an anhydrobiotic insect (Polypedilum vanderplanki) was successfully expressed in the engineered strains and the intracellular trehalose was efficiently secreted to the medium. As the results, the engineered strain co-expressing maltooligosyl trehalose synthase (MTS), maltooligosyl trehalose trehalohydrolase (MTH) and TRET1 secreted 97% of trehalose to the medium, and the titer was up to 2.7 g/L in 15 days. In addition, 5.7 g/L trehalose was produced by semi-continuous cultivation in 34 days. Taken together, this work demonstrates cyanobacteria can be applied as cell factories for direct sunlight-driven conversion of CO₂ into excreted trehalose.     

Effects of taurine supplementation on productive performance,nutrient digestibility and gene expression of nutrient transporters in quails reared under heat stress

This study was conducted to examine the effects of dietary taurine supplementation on productive performance, nutrient digestibility, antioxidant status, and the gene expression of ileal nutrient transporters in laying quails reared under heat stress (HS). One hundred and eighty laying Japanese quails (Coturnix coturnix japonica) were fed a basal diet or basal diet supplemented with either 2.5 or 5 g of taurine per kg of diet, and reared at either 22 ± 2 °C for 24 h/d (thermoneutral, TN) or 34 ± 2 °C for 8 h/d (HS) for 12 weeks. The quails reared under HS consumed less feed, produced less egg, and had lower dry matter, organic matter and crude protein apparent digestibilities compared with the quails reared under the TN condition (P = 0.001). However, increasing taurine concentrations in the diet improved feed intake and egg production (P = 0.001), but also the apparent digestibilities (P ≤ 0.027) in quails reared under HS. The greater doses (5 g/kg) of taurine resulted in more responses. The quails reared under HS had greater serum and liver MDA concentrations (P = 0.0001) which decreased with dietary taurine supplementations, particularly greater doses. The gene expressions of ileal PEPT1, EAAT3, CAT1, CAT2, SGLT1, SGLT5, GLUT2, and GLUT5 decreased under HS conditions (P = 0.001). However, supplementing taurine, in a dose-dependent fashion, to the diet of quails reared under HS resulted in increases in the gene expressions of the transporters (P < 0.05) except for CAT1. The results of the present work showed that taurine supplementation, particularly with greater doses (5 g/kg), to the diet of laying quails kept under HS acts as alleviating negative effects of HS, resulting in improvements in productive performance and nutrient digestion, and also upregulation of ileal nutrient transporters.     

Optimization of growing conditions for pigments production from microalga Navicula incerta using response surface methodology and its antioxidant capacity

Navicula incerta is a marine microalga distributed in Baja California, México, commonly used in aquaculture nutrition, and has been extended to human food, biomedical, and pharmaceutical industries due to its high biological activity. Therefore, the study aimed to optimize culture conditions to produce antioxidant pigments. A central composite experimental design and response surface methodology (RSM) was employed to analyze the best culture conditions. The medium (nitrogen-deficient concentrations), salinity (PSU = Practical Salinity Unity [g/kg]), age of culture (days), and solvent extraction (ethanol, methanol, and acetone) were the factors used for the experiment. Chlorophyll a (Chl a) and total carotenoids (T-Car), determined spectroscopically, were used as the response variables. The antioxidant capacity was evaluated by DPPH^? and ABTS^?+ radical inhibition, FRAP, and anti-hemolytic activity. According to the overlay plots, the optimum growth conditions for Chl a and T-Car production were the following conditions: medium = 0.44 mol·L^-1 of NaNO₃, salinity = 40 PSU, age of culture: 3.5 days, and solvent = methanol. The pigment extracts obtained in these optimized conditions had high antioxidant activity in ABTS^?+ (86.2–92.1% of inhibition) and anti-hemolytic activity (81.8–96.7% of hemolysis inhibition). Low inhibition (33–35%) was observed in DPPH^?. The highest value of FRAP (766.03 ± 16.62 μmol TE/g) was observed in the acetonic extract. The results demonstrated that RSM could obtain an extract with high antioxidant capacity with potential applications in the biomedical and pharmaceutical industry, which encourages the use of natural resources for chemoprevention of chronic-degenerative pathologies.