Staphylococcus lugdunensis infections: high frequency of inguinal area carriage.

Following a change in surgical practice, we noted that the rate at which Staphylococcus lugdunensis was isolated from samples from the plastic surgery unit of our hospital increased considerably. We investigated the sources of these S. lugdunensis strains, and we found that in the case of drain colonization or surgical site infection, the strain was more likely to have come from the patient's skin bacteria when the pubic site had been shaved preoperatively. To test the hypothesis of pubic site colonization, we evaluated the prevalence of S. lugdunensis carriage among the cutaneous flora of the inguinal area. We found that 22% of 140 incoming patients carried S. lugdunensis in this area and that carriage at both inguinal folds was frequent (68% of carriers). A study of the genetic structure of the total population, including the clinical (n = 18) and the commensal (n = 53) strains, revealed that the diversity of the species was low and that the population was composed of two major groups that diverged at a distance of 35%. No particular characteristics made it possible to distinguish between clinical and commensal strains. Only isolates producing beta-lactamase were homogeneous; six of the eight beta-lactamase-positive strains displayed the same pulsed-field gel electrophoresis pattern.

Extraction of cytochrome c in sodium dodecylbenzenesulfonate microemulsions.

The partition of cytochrome c between an aqueous phase in equilibrium with a microemulsion composed of sodium dodecylbenzenesulfonate, butanol, and decane was studied. By adjusting the pH and the ionic strength in the aqueous phase, cytochrome c can be quantitatively extracted in the microemulsion as long as the protein concentration in the organic phase is less than the initial concentration of micelles. Above this limit, an intermediate phase, containing part surfactant and part cytochrome c, is located between the aqueous and microemulsion phases. The role of electrostatic interactions in the protein partitioning is shown by varying the composition of the phases (pH, salinity, surfactant, and cosurfactant concentrations) and then discussed. Extraction depends on the relative values of the pH of the aqueous phase and the pI of cytochrome c, the size of the micelles, and the protonation of acidic residues. Cytochrome c can be recovered in an aqueous phase by adding butanol in the microemulsion phase. In such conditions, cytochrome c retains 90% of its initial activity, as measured before the extraction step.

Ethanol extraction by supported liquid membrane during fermentation.

A supported liquid membrane system was developed for the extraction of ethanol during semicontinuous fermentation of Saccharomyces bayanus. it consisted of a porous Teflon sheet as support, soaked with isotridecanol. This assembly permitted combining biocompatibility, permeation efficiency, and stability. The removal of ethanol from the cultures led to decreased inhibition and, thus, to a gain in conversion of 452 g/L glucose versus 293 g/L glucose without extraction. At the same time, the ethanol volumetric productivity was enhanced 2.5 times, due to an improvement of yeast viability, while the substrate conversion yield was maintained above 95% of its theoretical value. Besides these improvements in fermentation performances, the process resulted in ethanol purification, since the separation was selective towards microbial cells and carbon substrate, and likely selective to mineral ions present in the fermentation broth. For pervaporation, a concentration of ethanol four times greater was obtained in the collected permeate.

Extractive acetonobutylic fermentation by coupling ultrafiltration and distillation.

An extractive acetonobutylic fermentation process is developed by integrating bioproduction, Ultrafiltration, and distillation, providing simultaneous retention of biomass, selective removal of inhibitors from the permeate, as well as separation and purification of acetone-butanol-ethanol solvents. Successive batch fermentations were performed with normal pressure distillation (98 degrees C), which permitted prolonging and enhancing (by a factor of 3) solvent production, with very few volume exchanges of medium (average dilution rate ws 0.002 h(-1)), and recovering on-line concentrated solvents. Different operating conditions were also tested in order to study the presence of extracellular autolytic enzymes as inhibition factors: It was shown that, (1) extracellular autolytic activity remains low during the larger part of fermentations, even without enzyme-inactivating thermotreatment in the distillation boiler, and (2) high-temperature distillation causes deleterious effects to the culture medium for long duration treatments. Progressive improvements of the process were achieved, first, by managing continuous runs, providing a minimum renewal of the culture medium and, mainly, by decreasing temperature and pressure of distilation. Solvent productivity then reached 2.6 g/L h for a 0.036 h(-1) average dilution rate, corresponding to a feed concentration of 156 g/L glucose actually consumed.

Separation of L-valine from fermentation broths using a supported liquid membrane.

A carrier-mediated counter transport process is proposed to separate and to purify an amino acid produced by microbial fermentation. The case of L-valine permeation through a liquid membrane, constituted by a solution of Aliquat 336 in decanol and supported by a hydrophobic microporous membrane, is reported. A mathematical model was developed to estimate distribution coefficients and permeabilities and to predict the influence of hydrodynamic and pH conditions on supported liquid membrane (SLM) performances. Optimum conditions for the transport and the concentration of valine were achieved with synthetic aqueous valine solutions. Series of experiments on fermentation broths, where molasses and biomass contents were varied, permitted pointing out the role of the broth composition on the kinetics and yields of separation. The selectivity of transport of valine by an Aliquat 336/decanol liquid membrane was about 10 toward molasses dyes, 100 toward glucose, and beyond 1000 toward sucrose. This allowed us to achieve the recovery and one step of purification of the product in a single operation. The stability of the Aliquat 336/decanol liquid membrane was sufficient to ensure a selective transport of valine during a continuous run lasting 18 days.

Acetonobutylic fermentation: improvement of performances by coupling continuous fermentation and ultrafiltration.

The technology of coupling ultrafiltration and fermentation has been tested with the acetonobutylic fermentation in continuous mode. The device developed was sterilizable by steam and permitted drastic cleaning of the ultrafiltration (UF) membrane without interrupting the continuous fermentation. It has been shown to be an easily operated and reliable experimental tool for studying high-cell-density cultures and inhibition phenomena. With total recycle of biomass, a dry weight concentration of 125 g/L was attained, which greatly enhanced the volumetric solvent productivity of acetonobutylic fermentation in averaging 4. 5 g/L h for significant periods of time (>70 h) and maintaining solvent concentration and yield at acceptable levels.

Ethanol production by extractive fermentation.

The ideal method to produce a terminal metabolite inhibitor of cell growth and production is to remove and recover it from the fermenting broth as it formed. Extractive fermentation is achieved in the case of ethanol production by coupling both fermentation and liquid-liquid extraction, The solvent of extraction is 1-dodecanol (or a mixture 1-dedecanol, 1-tetradecanol); study of the inhibitory effect of primary aliphatic alcohols of different chain lengths shows that no growth is observed in the presence of alcohols which have between 2 and 12 carbons. This effect is suppressed when the carbon number is 12 or higher. A new reactor has been used-1 pulsed packed column. Pulsation is performed pneumatically. Porous material used as a package adsorbs the cells. The fermentation broth is pulsed in order to (1) increase the interfacial area between the aqueous phase and the dodecanol, (2) decrease gas holdup. Alcoholic fermentation, performed at 35 degrees C on glucose syrup, permits the total utilization of glucose solution of 409 g/L with a yeast which cannot-in classical process- completely use solutions with 200 g/L of glucose. The feasibility of a new method of fermentation coupling both liquid-liquid extraction and fermentation is demonstrated. Extension of this method is possible to any microbial production inhibited by its metabolite excretion.

Distribution, metabolism, and elimination of phenobarbital in rats: physiologically based pharmacokinetic model.

The distribution, metabolism, and elimination kinetics at two different doses of phenobarbital were examined in rats. After intravenous injection, phenobarbital distributed very rapidly to the liver and kidneys, less rapidly to the muscle and gut, and much more slowly to the brain. At the higher dose, a concentration rebound was observed 1 hr after injection. In addition, phenobarbital distributed unevenly in various organs as a result of a different extent of drug binding. A physiologically based model, including enterohepatic cycling and diffusion resistances between blood and tissue, is proposed for phenobarbital pharmacokinetics. It satisfactorily describes phenobarbital distribution in rats at the two doses and allows an evaluation of fundamental physicobiochemical parameters such as drug-tissue binding constants, blood-tissue transport coefficients, metabolism, and elimination rate constants.