Biosynthesis of pyocyanin pigment by Pseudomonas aeruginosa

Sixty-three isolates belonging to the genus Pseudomonas were isolated from different environmental sources including; soil, water and clinical specimens. Twenty out of them were identified as Pseudomonas aeruginosa and individually screened for pyocyanin production. P. aeruginosa R1; isolated from rice-cultivated soil and P. aeruginosa U3 selected from clinical specimen (Urinary tract infection) were the highest pyocyanin producers; pyocyanin production reached 9.3 and 5.9 μg/ml, respectively on synthetic glucose supplemented nutrient medium (GSNB). The identification of both selected strains (P. aeruginosa R1 and P. aeruginosa U3) was confirmed by 16S rRNA, the similarity with other strains available in database was 97% (with P. aeruginosa FPVC 14) and 94% (with P. aeruginosa 13.A), respectively. P. aeruginosa R1 and P. aeruginosa U3 are accessed at gene bank with accession numbers KM924432 and KM603511, in the same order. Pyocyanin was extracted by standard methods, purified by column chromatography and characterized by UV-Vis absorption, mass spectrometry and nuclear magnetic resonance. The antimicrobial activity of purified pyocyanin against multi-drug resistant microbes was investigated; the efficiency of pyocyanin was more obvious in Gram +ve bacteria than Gram−ve bacteria and yeast. To reduce the cost of pyocyanin production, a new conventional medium based on cotton seed meal supplemented with peptone was designed. The pyocyanin production of both selected strains P. aeruginosa R1 and P. aeruginosa U3 using the new medium is increased by 30.1% and 17.2%, respectively in comparison with synthetic GSNB medium, while the cost of production process is reduced by 56.7%.