Determining the disinfection of textiles in compressed carbon dioxide using various indicator microbes.

AIMS: This paper presents a research on the disinfection efficiency of inoculated textile swatches by compressed carbon dioxide, an environmental friendly way to disinfect textiles as opposed to the conventional laundering procedures using water. The disinfection efficiency was determined by using the following microbes inoculated on cotton test fabrics: Enterococcus faecium, Enterobacter aerogenes and Candida albicans. METHODS AND RESULTS: The experiments were performed using the high pressure extraction device with a maximum pressure of 50MPa and a small extraction vessel of 500ml. Pure CO(2) and CO(2) with added disinfection agent or commercial detergent were used. The chosen disinfecting agent was hydrogen peroxide, a widespread disinfecting chemical. It was found that treatment with CO(2) for 25min at 5MPa and 40°C (313K) and the addition of 4ml of specific detergent per litre of CO(2) assures at least a five log step reduction of Enterobacter aerogenes and C. albicans, whilst treatment at 50°C (323K) with CO(2) for 25min at 5MPa is sufficient for at least a five log step reduction for Enterococcus faecium. It was also found that a 15-min CO(2) treatment at 7MPa and 20°C (293K) was sufficient for the inactivation of the yeast C. albicans, whilst these conditions were not rigorous enough for the challenge bacteria. On the other hand, the labscale treatment with CO(2) for 25min at pressure 4 and 6MPa with the addition of detergent or hydrogen peroxide only yields a log step reduction of up to 4 log steps, thus proving the slightly disinfective properties of the CO(2) treatment with added agents, but not reaching efficient results as a 5 log step reduction was not reached. CONCLUSIONS: Addition of heat to the compressed CO(2) treatment of textiles inoculated with microorganisms proved more effective than the addition of detergent or disinfectant with compressed CO(2) treatment at temperature of 20°C. SIGNIFICANCE AND IMPACT OF THE STUDY: CO(2) treatment of textiles is a promising ecological alternative dry-cleaning method for the disinfection of medical textiles.

Hydrolases in supercritical CO2 and their use in a high-pressure membrane reactor.

The thermal stability and activity of enzymes in supercritical carbon dioxide (SC CO(2)) and near-critical propane were studied at a pressure of 300 bar in the temperature range 20-90 degrees C. Proteinase from Carica papaya was incubated in microaqueous SC CO(2) at atmospheric pressure in a nonaqueous system. Lipase stability in an aqueous medium at atmospheric pressure and in SC CO(2) as well as near-critical propane at 100 bar and 40 degrees C was studied. In order to investigate the impact of solvent on lipases, these were chosen from different sources: Pseudomonas fluorescences, Rhizpous javanicus, Rhizopus niveus and porcine pancreas. On the basis of our previous study on lipase activities in dense gases, a high-pressure continuous flat-shape membrane reactor was designed. The hydrolysis of sunflower oil in SC CO(2) was performed as a model reaction in this reactor. The reaction was catalyzed by the lipase preparation Lipolase 100T and was performed at 50 degrees C and 200 bar.

Micronization of drugs using supercritical carbon dioxide.

Particles from gas saturated solutions, a novel method for high pressure material processing, has been used for micronization of practically insoluble calcium-channel blockers nifedipine and felodipine and the hypolipidemic agent fenofibrate with the aim of increasing their dissolution rate and hence their bioavailability. Dependent on the pre-expansion conditions, a mean particle size of between 15 and 30 microm was achieved for micronized nifedipine and 42 microm for micronized felodipine. The particle size of processed fenofibrate, on the other hand, increased due to agglomeration. The highest dissolution rate was achieved by preparation of drug coprecipitates with PEG 4000.