Carbon metabolism inSulfobacillus thermosulfidooxidans subsp.asporogenes, strain 41

The activities of carbon metabolism enzymes were determined in cellular extracts of the moderately thermophilic, chemolithotrophic, acidophilic bacteriumSulfobacillus thermosulfidooxidans subsp.asporogenes, strain 41, grown either at an atmospheric content of CO₂ in the gas phase (autotrophically, heterotrophically, or mixotrophically) or autotrophically at a CO₂ content increased to 5–10%. Regardless of the growth conditions, all TCA cycle enzymes (except for 2-oxoglutarate dehydrogenase), one glyoxylate bypass enzyme (malate synthase), and some carboxylases (ribulose bisphosphate carboxylase, pyruvate carboxylase, and phosphoenolpyruvate carboxylase) were detected in the cell-free extracts of strain 411. During autotrophic cultivation of strains 41 and 1269, the increase in the CO2 content of the supplied air to 5–10% resulted in the activation of growth and iron oxidation, a 20–30% increase in the cellular content of protein, enhanced activity of the key TCA enzymes (citrate synthase and aconitase), and, in strain 41, a decrease in the activity of carboxylases.     

Development of phenylthiourea derivatives as allosteric inhibitors of pyoverdine maturation enzyme PvdP tyrosinase

Infections caused by Pseudomonas aeruginosa become increasingly difficult to treat because these bacteria have acquired various mechanisms for antibiotic resistance, which creates the need for mechanistically novel antibiotics. Such antibiotics might be developed by targeting enzymes involved in the iron uptake mechanism because iron is essential for bacterial survival. For P. aeruginosa, pyoverdine has been described as an important virulence factor that plays a key role in iron uptake. Therefore, inhibition of enzymes involved in the pyoverdine synthesis, such as PvdP tyrosinase, can open a new window for the treatment of P. aeruginosa infections. Previously, we reported phenylthiourea as the first allosteric inhibitor of PvdP tyrosinase with high micromolar potency. In this report, we explored structure-activity relationships (SAR) for PvdP tyrosinase inhibition by phenylthiourea derivatives. This enables identification of a phenylthiourea derivative (3c) with a potency in the submicromolar range (IC₅₀ = 0.57 + 0.05 µM). Binding could be rationalized by molecular docking simulation and 3c was proved to inhibit the bacterial pyoverdine production and bacterial growth in P. aeruginosa PA01 cultures.     

Polyphenolic extracts from pomegranate and watermelon wastes as substrate to fabricate sustainable silver nanoparticles with larvicidal effect against Spodoptera littoralis

The agricultural wastes adversely affect the environment; however, they are rich in polyphenols; therefore, this study aimed to employ polyphenol-enriched waste extracts for silver nanoparticles synthesis, and study the larvicidal activity of silver nanoparticles fabricated by pomegranate and watermelon peels extracts (PPAgNPs and WPAgNPs) against all larval instars of Spodoptera littoralis. The polyphenol profile of pomegranate and watermelon peel extracts (PP and WP) and silver nanoparticles was detected by HPLC. The antioxidant activity was estimated by DPPH, and FARP assays and the antimicrobial activity was evaluated by disc assay. The Larvicidal activity of AgNPs against Egyptian leaf worm was performed by dipping technique. The obtained AgNPs were spherical with size ranged 15–85 nm and capped with proteins and polyphenols. The phenolic compounds in silver nanoparticles increased about extracts; therefore, they have the best performance in antioxidant/reducing activity, and inhibit the growth of tested bacteria and yeast. The PPAgNPs were the most effective against the first instar larvae instar (LC₅₀ = 68.32 µg/ml), followed by pomegranate extract with (LC₅₀ = 2852 µg/ml). The results indicated that obvious increase in polyphenols content in silver nanoparticles enhance their larvicidal effect and increasing mortality of 1^st larval of S. littoralis Egyptian leafworms causing additive effect and synergism. We recommend recycling phenolic enriched agricultural wastes in producing green silver nanoprticles to control cotton leafworm that causes economic loses to crops.     

Iron availability increases the pathogenic potential of Salmonella typhimurium and other enteric pathogens at the intestinal epithelial interface

Recent trials have questioned the safety of untargeted oral iron supplementation in developing regions. Excess of luminal iron could select for enteric pathogens at the expense of beneficial commensals in the human gut microflora, thereby increasing the incidence of infectious diseases. The objective of the current study was to determine the effect of high iron availability on virulence traits of prevalent enteric pathogens at the host-microbe interface. A panel of enteric bacteria was cultured under iron-limiting conditions and in the presence of increasing concentrations of ferric citrate to assess the effect on bacterial growth, epithelial adhesion, invasion, translocation and epithelial damage in vitro. Translocation and epithelial integrity experiments were performed using a transwell system in which Caco-2 cells were allowed to differentiate to a tight epithelial monolayer mimicking the intestinal epithelial barrier. Growth of Salmonella typhimurium and other enteric pathogens was increased in response to iron. Adhesion of S. typhimurium to epithelial cells markedly increased when these bacteria were pre-incubated with increasing iron concentration (P = 0.0001), whereas this was not the case for the non-pathogenic Lactobacillus plantarum (P = 0.42). Cellular invasion and epithelial translocation of S. typhimurium followed the trend of increased adhesion. Epithelial damage was increased upon incubation with S. typhimurium or Citrobacter freundii that were pre-incubated under iron-rich conditions. In conclusion, our data fit with the consensus that oral iron supplementation is not without risk as iron could, in addition to inducing pathogenic overgrowth, also increase the virulence of prevalent enteric pathogens.     

Pregnancy and maternal iron deficiency stimulate hepatic CRBPII expression in rats

Iron deficiency impairs vitamin A (VA) metabolism in the rat but the mechanisms involved are unknown and the effect during development has not been investigated. We investigated the effect of pregnancy and maternal iron deficiency on VA metabolism in the mother and fetus. 54 rats were fed either a control or iron deficient diet for 2 weeks prior to mating and throughout pregnancy. Another 15 female rats followed the same diet and were used as non-pregnant controls. Maternal liver, placenta and fetal liver were collected at d21 for total VA, retinol and retinyl ester (RE) measurement and VA metabolic gene expression analysis. Iron deficiency increased maternal hepatic RE (P < .05) and total VA (P < .0001), fetal liver RE (P < .05), and decreased placenta total VA (P < .05). Pregnancy increased Cellular Retinol Binding Protein (CRBP)-II gene expression by 7 fold (P = .001), decreased VA levels (P = .0004) and VA metabolic gene expression (P < .0001) in the liver. Iron deficiency increased hepatic CRBPII expression by a further 2 fold (P = .044) and RBP4 by ~ 20% (P = .005), increased RBPR2 and decreased CRBPII, LRAT, and TTR in fetal liver, while it had no effect on VA metabolic gene expression in the placenta. Hepatic CRBPII expression is increased by pregnancy and further increased by iron deficiency, which may play an important role in VA metabolism and homeostasis. Maternal iron deficiency also alters VA metabolism in the fetus, which is likely to have consequences for development.     

Heterologous Expression of Lactose- and Galactose-Utilizing Pathways from Lactic Acid Bacteria in Corynebacterium glutamicum for Production of Lysine in Whey

The genetic determinants for lactose utilization from Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842 and galactose utilization from Lactococcus lactis subsp. cremoris MG 1363 were heterologously expressed in the lysine-overproducing strain Corynebacterium glutamicum ATCC 21253. The C. glutamicum strains expressing the lactose permease and β-galactosidase genes of L. delbrueckii subsp. bulgaricus exhibited β-galactosidase activity in excess of 1,000 Miller units/ml of cells and were able to grow in medium in which lactose was the sole carbon source. Similarly, C. glutamicum strains containing the lactococcal aldose-1-epimerase, galactokinase, UDP-glucose-1-P-uridylyltransferase, and UDP-galactose-4-epimerase genes in association with the lactose permease and β-galactosidase genes exhibited β-galactosidase levels in excess of 730 Miller units/ml of cells and were able to grow in medium in which galactose was the sole carbon source. When grown in whey-based medium, the engineered C. glutamicum strain produced lysine at concentrations of up to 2 mg/ml, which represented a 10-fold increase over the results obtained with the lactose- and galactose-negative control, C. glutamicum 21253. Despite their increased catabolic flexibility, however, the modified corynebacteria exhibited slower growth rates and plasmid instability.     

Antibiofilm activity and post antifungal effect of lemongrass oil on clinical Candida dubliniensis isolate

Candidal infections are often difficult to eradicate due to the resistance of biofilms to antifungal agents. This study aimed at determining the effects of lemongrass (Cymbopogon citratus DC) oil against Candida dubliniensis in both planktonic and biofilms form. The results from broth microdilution method revealed that the minimum inhibitory and minimum fungicidal concentration of lemongrass oil on C. dubliniensis were 0.43 and 0.86 mg/ml, respectively. Employing a formazan salt (XTT tetrazolium) reduction assay for biofilm study, the results showed that the average percentage (mean ± SD) inhibition of lemongrass oil (0.43 mg/ml) on biofilm formation was 91.57 ± 1.31%, while it exhibited more than 80% killing activity against C. dubliniensis in biofilm at concentrations of 1.7 mg/ml. In addition, a significant reduction (P = 0.03) of candidal adhesion to acrylic occurred after a 15 min exposure to 1.7 mg/ml of lemongrass oil. Moreover, limited exposure of yeasts to lemongrass oil at subcidal concentration can suppress growth for more than 24 h. Altogether, the results obtained indicate that lemongrass oil possessed antifungal and antibiofilm activities and could modulate candidal colonization. Therefore, the efficacy of lemongrass oil merits further development of this agent for the therapy of oral candidiasis.     

Bis-phosphonium salts of pyridoxine: The relationship between structure and antibacterial activity

A series of 23 novel bis-phosphonium salts based on pyridoxine were synthesized and their antibacterial activities were evaluated in vitro. All compounds were inactive against gram-negative bacteria and exhibited the structure-dependent activity against gram-positive bacteria. The antibacterial activity enhanced with the increase in chain length at acetal carbon atom in the order n-Pr > Et > Me. Further increasing of length and branching of alkyl chain leads to the reduction of antibacterial activity. Replacement of the phenyl substituents at the phosphorus atoms in 5,6-bis(triphenylphosphonio(methyl))-2,2,8-trimethyl-4H-[1,3]-dioxino[4,5-c]pyridine dichloride (compound 1) with n-butyl, m-tolyl or p-tolyl as well as chloride anions in the compound 1 with bromides (compound 14a) increased the activity against Staphylococcus aureus and Staphylococcus epidermidis up to 5 times (MICs = 1–1.25 μg/ml). But in practically all cases chemical modifications of compound 1 led to the increase of its toxicity for HEK-293 cells. The only exception is compound 5,6-bis[tributylphosphonio(methyl)]-2,2,8-trimethyl-4H-[1,3]dioxino[4,5-c]pyridine dichloride (10a) which demonstrated lower MIC values against S. aureus and S. epidermidis (1 μg/ml) and lower cytotoxicity on HEK-293 cells (CC₅₀ = 200 μg/ml). Compound 10a had no significant mutagenic and genotoxic effects and was selected for further evaluation. It should be noted that all bis-phosphonium salt based on pyridoxine were much more toxic than vancomycin.     

Glucose acts as a regulator of serum iron by increasing serum hepcidin concentrations

Mutual clinical and molecular interactions between iron and glucose metabolism have been reported. We aimed to investigate a potential effect of glucose on iron homeostasis. We found that serum iron concentrations gradually decreased over 180 min after the administration of 75 g of glucose from 109.8±45.4 mg/L to 94.4±40.4 mg/L (P<.001; N= 40) but remained unchanged in control subjects receiving tap water (N= 21). Serum hepcidin, the key iron regulatory hormone which is mainly derived from hepatocytes but also expressed in pancreatic β-cells, increased within 120 min after glucose ingestion from 19.7±9.9 nmol/L to 31.4±21.0 nmol/L (P<.001). In cell culture, glucose induced the secretion of hepcidin and insulin into the supernatant of INS-1E cultures, but did not change the amount of hepcidin detectable in the hepatocyte cell culture HepG2. We additionally confirmed the expression of hepcidin in a human islet cell preparation. These results suggest that glucose acts as a regulator of serum iron concentrations, most likely by triggering the release of hepcidin from β-cells.     

Chemical Composition and Antimicrobial Activity of the Essential Oil and Methanol Extract of Hypericum aegypticum subsp. webbii (Spach) N. Robson

Hypericum aegypticum subsp. webbii is an evergreen shrub spread in Mediterranean part of central and southeastern Europe. The chemical composition and antimicrobial activity of the essential oil and MeOH extract of H. aegypticum subsp. webbii were investigated. The monoterpenes α‐pinene (63.4 – 68.5%) and β‐pinene (16.9 – 17.0%) were main compounds in the volatile oil from aerial parts. In the cluster analysis, the essential oil of H. aegypticum subsp. webbii was separated and chemically different from the oil of other subspecies of H. aegypticum as well as other Hypericum species from Greece. SIMPER analysis revealed that α‐pinene (24.79%) was the component that contributed the most to differences between all oils. Also, there was extremely high overall dissimilarity between three subspecies of H. aegypticum. MeOH extract of aerial parts of H. aegypticum subsp. webbii contained flavonoids rutin (56.4 ± 0.9 mg/g), hyperoside and quercetin, and phenolic acids chlorogenic and caffeic acid, while naphthodianthrones were not detected. The antimicrobial activity of essential oil was moderate (MIC from 100 to >200 μg/ml), while MeOH extract inhibited the growth of Gram‐positive bacteria Bacillus subtilis, Enterococcus faecalis, Staphylococcus epidermidis, and Micrococcus luteus (MIC 50 – 100 μg/ml), more pronounced than the extract of H. perforatum (MIC 200 – >200 μg/ml).     

Hydrolytic and chromatographic studies on the PEGylation of dextranase from Penicillium sp.

Dextranases catalyze the hydrolysis of the α-l,6-glucosidic bond of the polysaccharide dextran. Dextranases have been isolated from bacteria, yeast and fungi. Purified dextranase enzyme from Penicillium sp. was PEGylated (polyethylene glycol modification) with mPEG (5000 Da) and showed an increase in the dextranase protein molecular weight as estimated by Superose 12 (23 ml) column and this increment in the molecular weight is directly proportional to mPEG (5000 Da) concentration until a complete dextranase enzyme PEGylation (disappearance of dextranase peak). The residual activity of partially PEGylated dextranase (mPEG 5000 of 5.8 mg/ml) was 33.8% and for the completely PEGylated dextranase (mPEG 5000 of 29 mg/ml) it was 25.75%. Dextranase PEGylated with mPEG (30,000 Da) showed a little PEGylation at mPEG concentration of 5.8 mg/ml but at a concentration of 29 mg/ml several PEGylated peaks were produced with a difference in dextranase activity toward dextran T500, retardation in the activity with the increasing in the molecular weight was clearly appeared with Sephadex G75 but for Sephadex G200 a little retardation than Sephadex G75 has been appeared.     

Antimicrobial potential of unstressed and heat stressed Allium sativum

Garlic (Allium sativum) is generally known to be of medicinal value, possessing potentials that include antimicrobial activity, but are often consumed in foods after subjection to cooking heat. The antimicrobial potential of heat stressed garlic may become decreased or lost when cooked, making its medicinal benefit unavailable to consumers. The potential of uncooked and cooked extracts from garlic imported to Jamaica, to inhibit the growth of eight microbes of clinical significance was investigated. Aqueous extracts of fresh garlic of 15 g/100 ml (fw), and dried and pulverized garlic cloves of 12.5 g/100 ml, 25 g/100 ml, 50 g/100 ml, and 100 g/100 ml (dw), were tested for inhibition of microbial growth. Extracts were tested uncooked, and cooked by boiling for 5, 10, and 15 min respectively. Of all the microbes studied, C. albicans incurred the largest zone of inhibition (57.7 ± 0.6 mm at the 100 g/100 ml of the dried extract, F(3, 8) = 51.778, p < 0.001, ω² = 0.93). Cooking of garlic extracts resulted in statistically significant decreases in zones of inhibition of microbes, as evident in the linear regression and one-way ANOVA analyses, and/or complete loss of microbial inhibition. C. albicans was the most inhibited microbe, followed by E. coli, and Salmonella sp., respectively. The use of uncooked garlic may be the best route for obtaining the greatest antimicrobial potential of garlic against susceptible bacteria and fungi because cooking heat stress resulted in the decrease and complete loss of the antimicrobial potentials of the garlic.     

Free radical formation and activity of antioxidant enzymes in lupin roots exposed to lead

Inhibition of root growth and modification of root morphology are the most sensitive responses of Lupinus luteus cv. Ventus L. to lead ions - Pb(NO₃)₂. Using electron paramagnetic resonance (EPR), we found that at the lead concentration of 150 mg.L^–1, the level of free radicals remained at control level, whereas at the higher, sublethal concentration of 350 mg.L^–1, they markedly increased. The EPR signal with the g-value at the maximum absorption of 2.0053 implied that the paramagnetic radical is derived from a quinone. The response of antioxidant enzymes, such as superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POX, EC 1.11.1.7) and ascorbate peroxidase (APOX, EC 1.11.1.11), to exogenously applied lead ions was also examined. Enzyme activity was estimated as a function of time and concentration. Native polyacrylamide gel electrophoresis followed by specific staining revealed an increase in the activity of SOD, CAT, POX and APOX coinciding with the time of cultivation. A lead-dependent increase in activities of SOD and POX from root tip extracts was observed, whereas CAT and APOX activities decreased at the higher lead concentrations. These results suggest that at higher lead concentrations, the formation of both free radicals and reactive oxygen species is beyond the capacity of the antioxidant system, which in turn may contribute to the reduced root growth.     

Utilization of drought-tolerant bacterial strains isolated from harsh soils as a plant growth-promoting rhizobacteria (PGPR)

Drought stress adversely affects plant health and productivity. Recently, drought-resistant bacterial isolates are used to combat drought resistance in crops. In this in vitro study, 20 bacterial isolates were isolated from harsh soil; their drought tolerance was evaluated using four concentrations of polyethylene glycol (PEG) 6000. The two most efficient isolates (DS4 and DS9) were selected and identified using 16S rRNA genetic sequencing. They were registered in the NCBI database and deposited under accession numbers MW916285 and MW916307 for Bacillus cereus (DS4) and Bacillus albus (DS9), respectively. These isolates were screened for plant growth-promoting properties compared to non-stressed conditions. Biochemical parameters; Proline, salicylic acid, gibberellic acid (GA), indole acetic acid (IAA), antioxidant activity, and antioxidant enzymes were measured under the same conditions, and in vitro seed germination was tested under stress conditions and inoculation with selected isolates. The results showed that under the harsh conditions of PEG6000, DS4 produced the highest amount of IAA of 1.61 µg/ml, followed by DS9 with 0.9 µg/ml. The highest amount of GA (49.95 µg/ml) was produced by DS9. On the other hand, the highest amount of siderophore was produced from DS4 isolate followed by DS9. Additionally, DS4 isolate recorded the highest exopolysaccharide (EPS) content of 3.4 mg/ml under PEG (-1.2 MPa) followed by DS9. The antioxidant activity increased in PEG concentrations depending manner, and the activity of the antioxidant enzymes increased, as catalase (CAT) recorded the highest activity in DS4 with an amount of 1.095 mg/ml. additionally, an increase in biofilm formation was observed under drought conditions. The isolated mixture protected the plant from the harmful effects of drought and showed an increase in the measured variables. Under unstressed conditions, the highest rates of emulsification index (EI 24%) were obtained for DS4 and DS9, at 14.92 and 11.54, respectively, and decreased under stress. The highest values of germination, total seedling length, and vigor index were obtained upon inoculation with the combination of two strains, and were 100%, 4.10 cm, and 410, respectively. Therefore, two strains combination is an effective vaccine capable of developing and improving drought tolerance in dryland plants.     

Potential effect of Allium sativum bulb for the treatment of biofilm forming clinical pathogens recovered from periodontal and dental caries

Biofilm producing clinical bacterial isolates were isolated from periodontal and dental caries samples and identified as, Lactobacillus acidophilus, Streptococcus sanguis, S. salivarius, S. mutansand Staphylococcus aureus. Among the identified bacterial species, S. aureus and S. mutansshowed strong biofilm producing capacity. The other isolated bacteria, Streptococcus sanguis, S. salivarius showed moderate biofilm formation. These pathogens were subjected for the production of extracellular polysaccharides (EPS) in nutrient broth medium and the strain S. aureus synthesized more amounts of EPS (610 ± 11.2 µg/ml) than S. sanguis (480 ± 5.8 µg/ml).EPS production was found to be less in S. salivarius (52 ± 3.8 µg/ml).The solvent extract of A. sativum bulb showed the phytochemicals such as, carbohydrate, total protein, alkaloids, saponins, flavonoids, tannins and sterioids. The solvent extract of A. sativum bulb showed wide ranges of activity against the selected dental pathogens. The difference in antibacterial activity of the solvent extract revealed differences in solubility of phytochemicals in organic solvents. Ethanol extract was highly active againstS. aureus (25 ± 2 mm). The Minimum Inhibitory Concentration (MIC) of crude garlic bulb varied widely and this clearly showed that bacteria exhibits different level of susceptibility to secondary metabolites. MIC value ranged between 20 ± 2 mg/ml and 120 ± 6 mg/ml and Minimum Bactericidal Concentration (MBC) value ranged from 60 ± 5 mg/l to 215 ± 7 mg/ml. To conclude, A. sativum bulb can be effectively used to treat periodontal and dental caries infections.     

Altered sphingolipid metabolism in human endometrial cancer

There is a growing body of evidence indicating that bioactive sphingolipids play a key role in cancer development, progression and metastasis. However, sphingolipid metabolism in malignant tumors is poorly investigated. Therefore, the aim of the present study was to examine the content of selected intermediates of ceramide metabolism and the activity of key enzymes of ceramide de novo synthesis and sphingosine-1-phosphate (S1P) production in the endometrial cancer. The specimens of cancer tissue and healthy endometrium were obtained from women undergoing surgery because of the cancer (n = 23) and because of myomas (n = 18), respectively. The content of sphinganine, dihydroceramide, ceramide, sphingosine and S1P was measured using high pressure liquid chromatography. The activity of the enzymes was determined using radioactive substrates. It has been found that the content of each examined sphingolipid was markedly elevated in the cancer tissue compared with the healthy endometrium. Namely, sphinganine, sphingosine and dihydroceramide by 3–4.6-fold, ceramide and S1P by 1.9- and 1.6-fold, respectively. Interestingly, the ratio of S1P to ceramide remained stable. The activity of serine palmitoyltransferase and sphingosine kinase 1 was increased by 2.3- and 2.6-fold, respectively. We conclude that endometrial carcinoma is characterized by profound changes in sphingolipid metabolism that likely contribute to its progression and chemoresistance.     

Development of a reproducible method to determine minimum inhibitory concentration (MIC) of plant extract against a slow-growing mycoplasmas organism

Mycoplasma species are fastidious bacteria that require a specialized medium for their growth, isolation and identification. There are no standardized tests to evaluate the in vitro susceptibility of mycoplasmas to medicinal plant extracts. A widely used in-broth, microtitre plate, minimum inhibitory concentration (MIC) assay was adapted and evaluated using acetone extracts of Anoigeissus leiocarpus on the isolates of Mycoplasma mycoides subsp. mycoides small colony variants (MmmSC). Several problems were encountered including the contamination of the medium by Bacillus species found in plants and the fact that the slow-growing mycoplasmas proved to be poor reducers of the indicator tetrazolium salt or resorcinol. We then examined a pH indicator-dependant technique to detect the acid production caused by the growth of the organism after glucose utilization from the broth medium. The method gives a clear cut-off point that was easy to read and interpret and was also reproducible.The MIC value for acetone extract of A. leiocarpus was 0.16 mg/ml. The development of this method now makes it possible to evaluate extracts of several plant species for antimycoplasmal activity.     

Anticonvulsant and analgesic in neuropathic pain activity in a group of new aminoalkanol derivatives

As part of the presented research, thirteen new aminoalkanol derivatives were designed and obtained by chemical synthesis. In vivo studies (mice, i.p.) showed anticonvulsant activity (MES) of nine compounds, and in the case of one compound (R,S-trans-2-((2-(2,3,5-trimethylphenoxy)ethyl)amino)cyclohexan-1-ol, 4) both anticonvulsant (ED₅₀ MES = 15.67 mg/kg, TD₅₀ rotarod = 78.30 mg.kg, PI = 5.00) and analgesic activity (OXA-induced neuropathic pain, active at 15 mg/kg). For selected active compounds additional in vitro studies have been performed, including receptor studies (5-HT_1A), evaluation of antioxidant activity (DPPH assay), metabolism studies as well as safety panel (mutagenicity, safety in relation to the gastrointestinal flora, cytotoxicity towards astrocytes as well as impact on their proliferation and cell cycle).     

Effect of iron and aeration on superoxide dismutase and catalase activity of PHB-producing Azotobacter chroococcum

The effect of aeration level and iron concentration on Azotobacter chroococcum 23 growth, PHB accumulation and antioxidative enzyme activities was investigated in shake flask experiments. Biomass yield and carbon source conversation coefficients increased in the presence of iron in the growth medium and under decreased aeration. The highest biomass production was observed for the culture grown in a medium with 36 μM of initial iron concentration and moderate aeration level. The highest PHB accumulation level (70–72% from cell dry weight) under our experimental conditions was observed at decreased aeration in the growth medium with 180 μM of initial iron concentration. Results obtained prove that both aeration level and iron supply have a marked influence on the activity of SOD and catalase. Bearing in mind the necessity of iron for the synthesis of both enzymes, only catalase showed a specific dependence on the intracellular iron accumulation level.