A Simple Characterisation of Violacein Compound Derived from Chromobacterium sp. strain Dyh27s2016 and its Antimicrobial Activity Against Pseudomonas aeruginosa

Chromobacterium sp. strain Dyh27s2016 was isolated from the lake at Manipal International University. Its purple pigmented violacein is hypothesised for a broad spectrum of intriguing biological properties, specifically as an antibacterial agent against Gram-negative bacteria. Hence, the current study aimed to isolate, characterise, and review the antimicrobial property of violacein from the Dyh27s2016 strain against P. aeruginosa. The bacterial strain was cultured in nutrient broth with L-tryptophan (0.1 mg/ml); after 24 h, the bacteria were lysed with methanol (3:1 ratio) and mixed with ethyl acetate (4:1 ratio). The top layer was then separated to obtain a concentrated purple pigment. The pH was changed at varying ranges and measured with UV/Vis to characterize this pigment. Then the antimicrobial test was performed against P. aeruginosa using the microdilution method and gauged its minimal inhibitory concentration (MIC). Violacein pigment derived from Chromobacterium violacein was used as a control in all experiments. For the result, crude violacein from Chromobacterium sp. strain Dyh27s2016 was obtained, and the purple pigment in different pH was observed in varying colours; the compound was particularly decolourised at a highly alkaline solution. The pigment was also able to significantly inhibit the growth of P. aeruginosa from 200 µg/mL - 800 µg/mL. Tests show that this pigment has a maximum absorption of light wavelength at approximately 600 nm and antibiotic test results show that the pigment can be considered a potential antimicrobial drug against P. aeruginosa.