Pyocyanin was the first natural phenazine described. The molecule is synthesized by about 95% of the strains of Pseudomonas aeruginosa. From discovery up to now, pyocyanin has been characterised by a very rich and avant-garde history, which includes its use in antimicrobial therapy, even before the discovery of penicillin opened the era of antibiotic therapy, as well as its use in electric current generation. Exhibiting an exuberant blue colour and being easy to obtain, this pigment is the subject of the present review, aiming to narrate its history as well as to unveil its mechanisms and suggest new horizons for applications in different areas of engineering, biology and biotechnology.

Significance and impact of the study: Microorganisms such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica serovar Enteritidis and S. enterica subsp. enterica serovar Typhimurium can cause contamination in fresh or processed food products. The use of natural compounds, for instance carvacrol, can be an alternative to the use of synthetic bactericides. Our data demonstrate that the carvacrol nanoemulsion (NECV) had stability for up to 90 days, promoted inhibitory activity against all evaluated microorganisms , and improved antimicrobial activity against P. aeruginosa, S. aureus and S. Typhimurium when compared to free oil. These findings suggest that NECV can be evaluated as a food preservative to promote antimicrobial activity.

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Recebido em 5/2/10; aceito em 23/8/10; publicado na web em 30/11/10Alternatives for the removal of high-molecular weight polycyclic aromatic hydrocarbons (HWM-PAH) from soil were tested by adding fertilizer or glycerol, as well as the combination of both. Experiments were carried out for 60 days in reactors containing a HWM-PAH-contaminated soil (8030 μg kg -1 ), accompanied by pH monitoring, humidity control and quantification of total heterotrophic bacteria and total fungus. Fertilizer addition removed 41.6% of HWM-PAH. Fertilizer and glycerol in combination removed 46.2%. When glycerol was added individually, degradation reached 50.4%. Glycerol also promoted the increase of degradation rate during the first 30 days suggesting the HMW-PAH removal occurred through cometabolic pathways.