The Potential of Natural Leaf Extracts as Green Inhibitors for Mild Steel Corrosion in Hydrochloric Acid Solutions

The inhibitive and thermodynamic behavior of Abelmoschus Esculentus and Citrus Maxima leaf extracts on the corrosion of mild steel in Hydrochloric acid solutions were investigated using potentiodynamic polarization curves measurements and electrochemical impedance spectroscopy (EIS) technique. Fourier transform infrared spectroscopy (FTIR) was done to predict some suggested chemical constituent of both leaf extracts. At any given concentration Abelmoschus Esculentus leaf extract is more efficient as a corrosion inhibitor for mild steel in 0.5 M HCl solutions than Citrus Maxima leaf extract. Potentiodynamic polarization curves indicated that both leaf extracts act as mixed type inhibitors for mild steel in 0.5 M HCl solutions. The impedance responses indicated that the corrosion process takes place under activation control. The inhibition of these plant leaf extracts depends on the physical adsorption of the chemical constituents of the extracts on mild steel surface as confirmed by Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS)

Improved corrosion resistance of permanganate-phosphate conversion coat on steel surface by surfactants

Abstract In the present work, we studied the effect of the presence of different concentrations of each of Triton-X-100 and Tween-80 surfactants in the bath of permanganate-phosphate conversion coating (PPC) on the corrosion resistance and the microstructure of the prepared coats. The coats were investigated using a scanning electron microscope (SEM), an energy dispersive X-ray spectrometer (EDX), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization techniques. The SEM results show that, on addition of the surfactants to the PPC bath, the porosity of the coat decreases and the coating layer becomes more compact. EIS results indicated that the presence of 0.01 M Triton-X-100 or 0.01 M Tween-80 in the coating solution caused an increase in the protection efficiency of the coat up to 93.7% and 84.1%, respectively. The potentiodynamic polarization results indicated that the two surfactants mainly act as anodic inhibitors due to the adsorption of their molecules at the anodic sites of the surface of steel and retard its oxidation reaction. The EDX and XPS results confirmed the results of the other techniques. A mechanism for the role of the surfactants in the coating process was proposed using the results of XPS and the other techniques

Kinetics of oxidation of metals in the air at room temperature using EDX

The kinetics of oxidation of Zn, Cu, Ni and C. steel were studied using the surface techniques, SEM, EDX and XRD, and electrochemical impedance spectroscopy (EIS) technique. EDX results showed that the variation of weight percent oxygen (Wt% O) on the surface of the four metals with the exposure time gave the same behavior, there is an increase of Wt% O with increasing the exposure time until about 2 h followed by a plateau, then the Wt% O increases again with increasing the time of exposure than 4 h. Fitting the experimental data of the four metals to the kinetic laws of oxidation indicated that the logarithmic law was fitted in short exposure (0.5 – 4 h), however, the parabolic law was fitted in long exposure (6 – 10 h). The values of each logarithmic rate constant (kl) and parabolic rate constant (kp)for the four metals were calculated. The kinetic of oxidation of the metals under study with exposure time is confirmed utilizing XRD technique. The protective action of the air-formed oxide films was investigated by EIS technique. The electrochemical impedance spectroscopy results confirmed the EDX results

Isolation, screening and improvement of rhamnolipid production by <em>Pseudomonas</em> isolates

611-619Rhamnolipids (RLs) have attracted attention of many scientists because of their low toxicity, biodegradability and ecological acceptability. Nevertheless,their use is extremely limited due to the high cost when compared with chemical surfactants.Therefore,in this studya total of twenty four Pseudomonas isolates were recovered from various soil samples. Screening for RLs production was done using Siegmund Wagner agar plates where six isolates appeared to produce RLs. Isolate P6 was chosen as the most promising RL producer and identified using 16S rRNA sequencing as P. aeruginosa. The best production of 2.5 g/L was obtained by isolate P6 after six days of incubation at 30°C, 250 rpm. Random mutagenesis using UV or gamma radiation resulted in improved RL production by the mutants, the best of which was designated 15GR, which produced RL at concentrations two times higher that of the parent isolate. Rhamnolipids from this mutant showed improved activity and higher emulsifying power relative to that of the parent. Therefore, P6 isolate and its mutant 15GR are promising RL producers which have the advantage of producing RLs from glucose without induction with hydrophobic carbon sources

Evaluation of ELISA and immunoaffinity fluorometric analytical tools of four mycotoxins in various food categories

Abstract Mycotoxins (MTs) are secondary toxic metabolites that can contaminate food, impacting quality and safety, leading to various negative health effects and serious pathological consequences conferring urgent need to evaluate and validate the currently standard methods used in their analysis. Therefore, this study was aimed to validate ELISA and VICAM immunoaffinity fluorometric, the two common methods used to monitor the level of MTs according to the Egyptian Organization for Standardization and Quality Control. A total of 246 food samples were collected and tested for Aflatoxins (196 samples), Ochratoxin A (139), Zearalenone (70), and Deoxynivalenol (100) using both analytical methods. Results showed that aflatoxins exceeded limits in 42.9, 100, and 13.3% of oily seeds, dried fruits, and chili and spices, respectively. For ochratoxin A, 3.9% of Gramineae and 8% of spices and chili (locally sourced) exceeded the limits, while 17.6% of imported pasta and noodles exceeded the limits for deoxynivalenol. Significant differences for the aflatoxins and ochratoxin A detection among different categories of chocolate, dried fruits, and oily seeds (p-value  0.05). In conclusion, our study found no significant differences between the ELISA and immunoaffinity fluorometric analysis in the detection of the respective MTs in various food categories and therefore, they can substitute each other whenever necessary. However, significant differences were observed among different food categories, particularly the local and imported ones, highlighting the urgent need for strict and appropriate control measures to minimize the risk of MTs adverse effects

Rhamnolipid production by a gamma ray-induced Pseudomonas aeruginosa mutant under solid state fermentation

Abstract Solid-state fermentation has a special advantage of preventing the foaming problem that obstructs submerged fermentation processes for rhamnolipid production. In the present work, a 50:50 mixture of sugarcane bagasse and sunflower seed meal was selected as the optimum substrate for rhamnolipid production using a Pseudomonas aeruginosa mutant 15GR and an impregnating solution including 5% v/v glycerol. Using Box–Behnken design, the optimum fermentation conditions were found to be an inoculum size 1% v/v, temperature 30 °C and unlike other studies, pH 8. These optimized conditions yielded a 67% enhancement of rhamnolipid levels reaching 46.85 g rhamnolipids per liter of impregnating solution, after 10 days, which was about 5.5 folds higher than that obtained by submerged liquid fermentation. Although maximum rhamnolipids concentration was obtained after 10 days of incubation, rhamnolipids concentration already reached high levels (41.87 g/l) after only 6 days. This rhamnolipid level was obtained in a shorter time and using lower carbon source concentrations than most studies reported so far. The findings obtained indicate an enormous potential for employing solid-state fermentation for rhamnolipid production by the studied isolate

Influence of povidone-iodine on micro-tensile bonding strength to dentin under simulated pulpal pressure

Abstract Background Previous studies had reported that bond strength deteriorate over time following the dentin surface pretreatment with chlorhexidine. Therefore, further investigations are needed to evaluate the effect of other materials such as povidone iodine. The purpose of this study was to investigate the effects of 10% povidone-iodine pretreatment on the resin-dentin micro-tensile bond strength of a single bond adhesive system in permanent teeth over time, and compare it with 2% chlorhexidine. Methods Flat dentin surfaces were prepared in 63 extracted permanent teeth. Teeth were randomly assigned to a 10% povidone-iodine pretreatment, a 2% chlorhexidine pretreatment, or a control group. Composite resin blocks were built up over treated surfaces under pulp pressure simulation. The prepared specimens were assigned to three storage time, 24 h, 1 week, and 2 months. Samples were vertically sectioned to obtain specimens of 0.7 to 1.2 mm2 cross-sectional area. Results No significant reduction of bond strength of povidone iodine group was found among the three storage times (p = 0.477). A significant reduction of bond strength for both chlorhexidine and control groups was found in the three storage times (p <  0.001). Conclusion Povidone iodine pretreatment of etched dentin was effective in reducing the loss of bond strength over time, while the chlorhexidine pretreatment and negative control showed significant deterioration in micro-tensile bond strength over time in permanent teeth

Paromomycin production from Streptomyces rimosus NRRL 2455: statistical optimization and new synergistic antibiotic combinations against multidrug resistant pathogens

Abstract Background Response surface methodology (RSM) employing Box-Behnken design was used to optimize the environmental factors for the production of paromomycin, a 2 deoxystreptamine aminocyclitol aminoglycoside antibiotic, (2DOS-ACAGA) from Streptomyces (S.) rimosus NRRL 2455. Emergence of bacterial resistance caught our attention to consider the combination of antimicrobial agents. The effect of paromomycin combination with other antimicrobial agents was tested on some multiple drug resistant isolates. To the best of our knowledge, this is the first report on optimization of paromomycin production from S. rimosus NRRL 2455. A Quadratic model and response surface method were used by choosing three model factors; pH, incubation time and inoculum size. A total of 17 experiments were done and the response of each experiment was recorded. Concerning the effect of combining paromomycin with different antimicrobial agents, it was tested using the checkerboard assay against six multidrug resistant (MDR) pathogens including; Pseudomonas (P.) aeruginosa (2 isolates), Klebsiella (K.) pneumoniae, Escherichia (E.) coli, methicillin sensitive Staphylococcus aureus (MSSA) and methicillin resistant Staphylococcus aureus (MRSA). Paromomycin was tested in combination with ceftriaxone, ciprofloxacin, ampicillin/sulbactam, azithromycin, clindamycin and doxycycline. Results The optimum conditions for paromomycin production were a pH of 6, an incubation time of 8.5 days and an inoculum size of 5.5% v/v using the optimized media (soybean meal 30 g/L, NH4CL 4 g/L, CaCO3 5 g/L and glycerol 40 ml/L), 28 °C incubation temperature, and 200 rpm agitation rate that resulted in 14 fold increase in paromomycin production as compared to preliminary fermentation level using the basal medium. The tested antibiotic combinations showed either synergistic effect on paromomycin activity on most of the tested MDR pathogens (45.83%), additive effect in 41.67% or indifferent effect in 12.5%. Conclusion RSM using multifactorial design was a helpful and a reliable method for paromomycin production. Paromomycin combination with ceftriaxone, ciprofloxacin, ampicillin/sulbactam, azithromycin, clindamycin or doxycycline showed mostly synergistic effect on certain selected clinically important MDR pathogens

Lysinibacillus Isolate MK212927: A Natural Producer of Allylamine Antifungal &lsquo;Terbinafine&rsquo;

Resistance to antifungal agents represents a major clinical challenge, leading to high morbidity and mortality rates, especially in immunocompromised patients. In this study, we screened soil bacterial isolates for the capability of producing metabolites with antifungal activities via the cross-streak and agar cup-plate methods. One isolate, coded S6, showed observable antifungal activity against Candida (C.) albicans ATCC 10231 and Aspergillus (A.) niger clinical isolate. This strain was identified using a combined approach of phenotypic and molecular techniques as Lysinibacillus sp. MK212927. The purified metabolite displayed fungicidal activity, reserved its activity in a relatively wide range of temperatures (up to 60 &deg;C) and pH values (6&ndash;7.8) and was stable in the presence of various enzymes and detergents. As compared to fluconazole, miconazole and Lamisil, the minimum inhibitory concentration of the metabolite that showed 90% inhibition of the growth (MIC90) was equivalent to that of Lamisil, half of miconazole and one fourth of fluconazole. Using different spectroscopic techniques such as FTIR, UV spectroscopy, 1D NMR and 2D NMR techniques, the purified metabolite was identified as terbinafine, an allylamine antifungal agent. It is deemed necessary to note that this is the first report of terbinafine production by Lysinibacillus sp. MK212927, a fast-growing microbial source, with relatively high yield and that is subject to potential optimization for industrial production capabilities