Parietal Structures of Escherichia coli Can Impact the D-Cateslytin Antibacterial Activity.

Bacterial resistance to conventional antibiotics is of major concern. Antimicrobial peptides (AMPs) are considered excellent alternatives. Among them, D-cateslytin (D-Ctl, derivative of a host defense peptide) has shown high efficiency against a broad spectrum of bacteria. The first target of AMPs is the outer membrane of the bacterium. However, the role of bacterial cell-wall structures on D-Ctl's mechanism of action has not yet been understood. In this study, we investigated the activity of D-Ctl on two isogenic strains of E. coli: one is devoid of any parietal structures; the other constitutively overexpresses only type 1 fimbriae. We studied the damage caused by D-Ctl at several initial concentrations of bacteria and D-Ctl, and exposure times to D-Ctl were examined using a combination of epifluorescence microscopy, atomic force microscopy (AFM), and Fourier transform infrared spectroscopy in attenuated total reflectance mode (ATR-FTIR). The analysis of nanomechanical and spectrochemical properties related to the antibacterial mechanism showed a concentration dependent activity. Whereas the membrane permeabilization was evidenced for all concentrations of D-Ctl and both mutants, no pore formation was observed. The bacterial stiffness is modified dramatically concomitantly to major membrane damage and changes in the spectral fingerprints of the bacteria. In the case of the occurrence of type 1 fimbriae only, an intracellular activity was additionally detected. Our results evidenced that D-Ctl activity is highly impacted by the cell-wall external structures and surface properties of the bacteria.

Supercritical CO2 Extraction of Extracted Oil from Pistacia lentiscus L.: Mathematical Modeling, Economic Evaluation and Scale-Up.

In this study, the extracted oil of Pistacia lentiscus L. the Tunis region was extracted using supercritical carbon dioxide (SC-CO2) extraction containing different major components in the oil such as α-pinene (32%) and terpinene-4-ol (13%). The investigation of the effect of different variables on the extraction yield with 5% level of confidence interval showed that the CO2 pressure was the main significant variable to influence the oil yield. In order to better understand the phenomena, three parameters were considered to adjust all parameters of broken and intact cell (BIC) model: grinding efficiency (G), the internal mass transfer parameter ( k S a 0 ), and the external mass transfer parameter ( k f a 0 ), which were estimated by experimental extraction curves to calculate the diffusion coefficient. From an economic point of view, we found out that the high cost of production of the extracted oil was due to the low mass of extracted oil obtained from this type of plant.

Response surface methodology applied to Supercritical Fluid Extraction (SFE) of carotenoids from Persimmon (Diospyros kaki L.).

Supercritical carbon dioxide with ethanol as co-solvent was used to extract carotenoids from persimmon fruits (Diospyros kaki L.). Based on a response surface methodology (RSM), a predicting model describing the effects of CO2 temperature, pressure, flow rate, ethanol percentage and extraction time was set up for each of the four carotenoids of interest. The best extraction yields in our experimental domain were found at 300 bars, 60°C, 25% (w/w) ethanol, 3mL/min flow rate and 30min for xanthophylls (all-trans-lutein, all-trans-zeaxanthin and all-trans-ß-cryptoxanthin). The yields were 15.46±0.56, 16.81±1.74 and 33.23±2.91µg/g of persimmon powder for all-trans-lutein, all-trans-zeaxanthin and all-trans-ß-cryptoxanthin, respectively. As a non-oxygenated carotenoid, all-trans-ß-carotene was better extracted using 100 bars, 40°C, 25% (w/w) ethanol, 1mL/min flow rate and 30min extraction time, with an extraction yield of 11.19±0.47µg/g of persimmon powder.

Driving Forces Controlling Host-Guest Recognition in Supercritical Carbon Dioxide Solvent.

The formation of supramolecular host-guest complexes is a very useful and widely employed tool in chemistry. However, supramolecular chemistry in non-conventional solvents such as supercritical carbon dioxide (scCO2 ), one of the most promising sustainable solvents, is still in its infancy. In this work, we explored a successful route to the development of green processes in supercritical CO2 by combining a theoretical approach with experiments. We were able to synthesize and characterize an inclusion complex between a polar aromatic molecule (benzoic acid) and peracetylated-ß-cyclodextrin, which is soluble in the supercritical medium. This finding opens the way to wide, environmental friendly, applications of scCO2 in many areas of chemistry, including supramolecular synthesis, reactivity and catalysis, micro and nano-particle formation, molecular recognition, as well as enhanced extraction processes with increased selectivity.

Supercritical CO2 extraction of oil, fatty acids and flavonolignans from milk thistle seeds: Evaluation of their antioxidant and cytotoxic activities in Caco-2 cells.

The optimal conditions of supercritical carbon dioxide (SC-CO2) (160-220 bars, 40-80 °C) technology combined with co-solvent (ethanol), to recover oil, flavonolignans (silychristin, silydianin and silybinin) and fatty acids from milk thistle seeds, to be used as food additives and/or nutraceuticals, were studied. Moreover, the antioxidant and cytotoxic activities of the SC-CO2 oil seeds extracts were evaluated in Caco-2 carcinoma cells. Pressure and temperature had a significant effect on oil and flavonolignans recovery, although there was not observed a clear trend. SC-CO2 with co-solvent extraction at 220 bars, 40 °C was the optimum treatment to recover oil (30.8%) and flavonolignans from milk thistle seeds. Moreover, linoleic (47.64-66.70%), and oleic (19.68-24.83%) acids were the predominant fatty acids in the oil extracts recovered from milk thistle under SC-CO2. In addition, SC-CO2 extract showed a high antioxidant activity determined by DPPH and ABTS tests. Cytotoxic activities of silychristin, silydianin and silybinin and the obtained SC-CO2 extract (220 bars, 40 °C) were evaluated against Caco-2 cells. The SC-CO2 extract inhibited the proliferation of Caco-2 cells in a dose-responsive manner and induced the highest percentage of mortality of Caco-2 cells (from 43 to 71% for concentrations from 10 up to 100 µg/ml of SC-CO2 oil seeds).

Supercritical SC-CO(2) and Soxhlet n-Hexane Extract of Tunisian Opuntia ficus indica Seeds and Fatty Acids Analysis.

The fatty acids profiles of Tunisian Opuntia ficus indica seeds (spiny and thornless form) were investigated. Results of supercritical carbon dioxide (SC-CO(2)) and soxhlet n-hexane extract were compared. Quantitatively, the better yield was obtained through soxhlet n-hexane: 10.32% (spiny) and 8.91% (thornless) against 3.4% (spiny) and 1.94% (thornless) by SC-CO(2) extract (T = 40°C, P = 180 bar, time = 135 mn, CO(2) flow rate = 15 mL·s(-1)). Qualitatively, the main fatty acids components were the same for the two types of extraction. Linoleic acid was the major compound, SC-CO(2): 57.60% (spiny), 59.98% (thornless), soxhlet n-hexane: 57.54% (spiny), 60.66% (thornless), followed by oleic acid, SC-CO(2): 22.31% (spiny), 22.40% (thornless), soxhlet n-hexane: 25.28% (spiny), 20.58% (thornless) and palmitic acid, SC-CO(2): 14.3% (spiny), 12.92% (thornless), soxhlet n-hexane: 11.33% (spiny), 13.08% (thornless). The SC-CO(2) profiles fatty acids showed a richness with other minority compounds such as C(20:1), C(20:2), and C(22).The seeds oil was highly unsaturated (US = 4.44-5.25), and the rising temperatures donot affect the selectivity of fatty acids extract by SC-CO2: US = 4.44 (T = 40°C) and 4.13 (T = 70°C).