Optimization of Production Conditions of Natural Antibacterial Violacin Pigment from Janthinobacterium lividum

Janthinobacterium. lividum (J. lividum) is a bacterium that can produce a secondary metabolite with antimicrobial properties called violacein. Violacein is produced in this bacterium under special conditions, such as food stress, lack of oxygen, changes in pH or ambient temperature, and even in the presence of a chemical. Bacteria use these production factors as agents for greater survival. This pigment can be used to dye hospital textiles with antibacterial properties. This study aimed to determine the appropriate conditions for the maximum production of violacein pigment by bacteria to save production time and cost.

In this study, the effects of different treatments were tested quantitatively and qualitatively to achieve the best conditions for the production of violacein by J. lividum. Other evaluations included the effect of aeration on the production of color biofilm, the effect of temperature on the production of violacein, glycerol concentration test and its effect on pigment production, the effect of glycerol, sodium sulfate, tryptophan, meat extract and peptone on production optimization, optimization in a solid and liquid medium and color spectrum, and violet dye resistance at different pHs. The SPSS software and t-test were used for quantitative analysis and comparison of the treatments.

It was found that a culture medium containing meat extract (0.3%) and peptone (0.5%),  glycerol (1%), and tryptophan (1%) on a solid culture medium containing nutrient agar was selected as the best culture medium for the production of violacein. The amount of biomass and dye production in the solid medium was twice that in the liquid medium. The optimum condition for the production of violacein pigment in this strain included pH 7 and a temperature of 25 °C. The purple color of this pigment was stable for a long time (24 h) at acidic pH (up to pH 11).

Modified nutrient agar solid culture medium was introduced for optimal production of violacein. Optimal bacterial culture conditions (temperature 25 °C and pH 7) were obtained for the best pigment production. It can be concluded that natural dyes can replace harmful chemical dyes if produced in a product with high efficiency and quality. In this study, the production of violacein with more efficacy was tried through the enhancement and improvement of culture medium composition and maintenance of the optimal production conditions.