Phenolic content and antibiofilm activity of propolis against clinical MSSA strains

Antibiofilm properties and the phenolic composition of propolis, collected from Bartın province of Turkey in the years of 2013 and 2012, were determined. Hexane, ethyl acetate and ethanol extracts of propolis were prepared and assessed for their antibiofilm activity (inhibition of biofilm formation and reduction of established biofilm) against the clinical methicillin sensitive Staphylococcus aureus (MSSA) strains and Staphylococcus aureus ATCC 33862. Ethyl acetate and ethanol extracts of propolis presented a greater effectiveness on biofilm inhibition of the tested bacteria compared to hexane extracts. The activity patterns showed slight variations in the two years. While 0.5 mg/mL ethyl acetate, ethanol and hexane extract solutions of the product in 2013 inhibited 92.89, 82.98 and 47.42% of biofilm formation of MSSA M20 strain, the inhibition percentage of the products of 2012 were determined to be 87.14%, 75.94% and 44.89% against the same bacterium (MSSA M20), respectively. The results of the validated liquid chromatography-electrospray tandem mass spectrometry (UPLC-ESI-MS/MS) analyses showed a strong relation between the activity and the phenolic composition of the extracts. Phenolic contents of the ethyl acetate and ethanol extracts were relatively higher than hexane extracts. Caffeic acid composition of ethyl acetate, ethanol and hexane extracts of the product in 2013 was detected as 23521.0, 16881.0 and 3522.8 µg/g, respectively. On the other hand, the caffeic acid contents of the product of 2012 was found to be lower than those of 2013 (19100.0, 10416.0 and 2322.5 µg/g for ethyl acetate, ethanol and hexane extracts, respectively). Consequently, the findings have shown that propolis extracts possessed good antibiofilm activity against clinical staphylococci, and its phenolic composition has been affected by the year of collection. © 2016 ACG Publications. All rights reserved

Effect of environmental factors on biological reduction of hexavalent chromium by Pseudomonas mendocina

In this study, the effects of pH, initial chromium concentrations, organic acids (alginic acid, galacturonic acid, glucuronic acid and citric acid) and their binary combinations on the bacterial chromium reduction were investigated. The results revealed that the Cr(VI) reduction for Pseudomonas mendocina was high at optimum pH value (6). The Cr(VI) reduction rate of P. mendocina decreased with the increase in initial chromium concentration. The Cr(VI) reduction ability of the bacterium increased in the presence of organic acids especially galactronic acid and glucuronic acid. Binary combinations of galactronic acid and glucuronic acid caused a dramatic increase in the rate of chromate reduction. Experiments with heat-inactivated cells indicated that biosorption onto cell material had a negligible impact for the loss of Cr(VI) from the solution. As a result of SDS-PAGE analysis, it was observed a protein band approximately 31 kDa in periplasmic extracts of P. mendocina cells

Reduction of Cr(VI) to Cr(III) by thermal Bacillus licheniformis B22 under different temperatures using binary and ternary combinations of organic acids

This study presents optimization of process variables for hexavalent chromium reduction using thermotolerant Bacillus licheniformis B22 isolated from Pamukkale (Denizli, Turkey). We examined the effects of binary and ternary combinations of different electron-donating substrates (galacturonic acid, glucuronic acid, and humic acid) at 45 and 50°C. The influence of different pH values (6.0, 7.0, 8.0, 9.0, and 10.0) and initial inoculation rates (2, 4, 6, and 8%) were also enumerated. The strongest stimulatory effect on Cr(VI) reduction was obtained with ternary combination of galacturonic acid, glucuronic acid, and humic acid. At 45 and 50°C, 8% inoculation rate, the reduction in ternary combination is relatively fast, completely reducing 100 mg/l Cr(VI) in 6 h compared with 2% inoculation rate (12 h). This bacterium exhibited a rapid Cr(VI) reduction ability under optimized conditions. Cr(VI) reduction of B. licheniformis B22 increased with an increase in initial inoculation rate, and the optimum initial pH for Cr(VI) reduction was 7.0. In addition, the results suggested that the reduced Cr(III) was not precipitated in the form of Cr(OH)3, and that organic acids significantly enhanced microbial Cr(VI) reduction rates by forming less toxic and highly soluble organo-Cr(III) complexes despite Cr(III) having very low solubility

Antibiofilm Activity and Chemical Contents of Propolis Samples From Manisa-Turkey

In this study, the inhibition of biofilm formation and the reduction of preformed or established biofilm by ethanol extract of propolis samples (EEP) obtained from Manisa-Turkey was investigated and their chemical composition was screened. The antibiofilm effect of the propolis extracts against biofilm forming bacteria (Listeria monocytogenes ATCC 7644, Methicillin Sensitive Staphylococcus aureus (clinical isolate) MSSA M20, S. aureus ATCC 33862, S. aureus ATCC 29213, Enterococcus faecalis ATCC 19433, Pseudomonas fluorescens ATCC 55241, Micrococcus luteus NRRL-B1013) was tested on 96-well polystyrene plates using crystal violet assay. Also, the antibacterial activity of EEP was evaluated according to Agar Well Diffusion method. Chemical composition of extracts was detected by Gas Chromatography-Mass Spectrometry (GC/MSD) analyze. The EEP samples exhibited good antibiofilm activity against bacteria. The maximum biofilm inhibition activity percentage of MP-1 (Manisa-Köprübaşı), MP-2 (Manisa-Demirci) and MP-3 (Manisa-Kula) were found as 89.4%, 80.0% and 89.0% for L. monocytogenes ATCC 7644 and 66.0%, 67.0% and 74.0% for MSSA M20, respectively. According to GC/ MSD analyze, triacontyl acetate was the major compound found in propolis extracts

Effect of environmental factors on biological reduction of hexavalent chromium by Pseudomonas mendocina

In this study, the effects of pH, initial chromium concentrations, organic acids (alginic acid, galacturonic acid, glucuronic acid and citric acid) and their binary combinations on the bacterial chromium reduction were investigated. The results revealed that the Cr(VI) reduction for Pseudomonas mendocina was high at optimum pH value (6). The Cr(VI) reduction rate of P. mendocina decreased with the increase in initial chromium concentration. The Cr(VI) reduction ability of the bacterium increased in the presence of organic acids especially galactronic acid and glucuronic acid. Binary combinations of galactronic acid and glucuronic acid caused a dramatic increase in the rate of chromate reduction. Experiments with heat-inactivated cells indicated that biosorption onto cell material had a negligible impact for the loss of Cr(VI) from the solution. As a result of SDS-PAGE analysis, it was observed a protein band approximately 31 kDa in periplasmic extracts of P. mendocina cells

The Role of Different Metal and Heavy Metal Ions on Chromium Reduction by Pseudomonas mendocina DS0601- FX-P22

In this study, the effects of different metal ions such as $Mn^{2+}$, $Cu^{2+}$, $Fe^{2+}$, $Ba^{2+}$, $Al^{2+}$, $Ni^{2+}$, $Co^{2+}$, $Zn^{2+}$, $Cd^{2+}$ and $Pb^{2+}$ on the bacterial chromium reduction by Pseudomonas mendocina DS0601-FX-P22 were investigated. Two different initial chromium concentrations (15 mg/L and 25 mg/L Cr(VI)) were studied. The Cr(VI) reduction ability of the bacterium increased in the presence of metal ions like Cu2+ and Fe2+ and was significantly inhibited in the presence of metal ions like $Ba^{2+}$ and $Ni^{2+}$. Also, $Cu^{2+}$ was the most efficient metal ion at Cr(VI) reduction for both Cr(VI) concentration (15 and 25 mg/L) in P. mendocina DS0601-FX-P22 bacterium

Characterization of extracellular polysaccharides (EPS) produced by thermal bacillus and determination of environmental conditions affecting exopolysaccharide production

In this study, the neutral monosaccharide composition of the Extracellular Polysaccharide (EPS), extracted from thermal Bacillus, was determined by Liquid Chromatography-Mass Spectrometry and High Performance Liquid Chromatography. Our analysis indicated that the EPS consisted of rhamnose, mannose, galactose, glucose, fructose, arabinose and xylose. In addition to the neutral sugars in the EPS, it also contained 230 mg protein/g EPS and 17.18 mg uronic acid /g EPS. The X-ray diffraction data indicated mainly of amorphous nature (80 %) and the presence of chitin, chitosan, protein and calcite. Thermogravimetric analysis curve showed that degradation of EPS takes place in three steps (13.38% at 180 °C. 45.62% at 180-500 °C, 25.55% at > 500 °C) indicating moisture content and high content of carboxyl group, pyrolysis temperature and decomposition of calcite crystals, respectively. Additionally, laboratory batch experiments were performed characterize the effects of different natural organic acids, pH levels, temperatures and Cr(VI) concentrations on microbial EPS production by Bacillus licheniformis B22. Our results indicate that organic acids caused enhanced EPS release. Alginic acid was the most efficient organic acid at EPS production in B. licheniformis B22. The optimum pH level was 6.0-7.0 and the highest EPS production was observed at 50 °C for B. licheniformis B22. In addition, EPS production increased with increased chromium in the growth medium due to the toxic effect of Cr(VI) on cells. Maximum EPS production was observed when 150 mg/L Cr(VI) was added to the medium. © 2015, University of Tehran. All rights reserved