Optimization of melanin production by Brevundimonas sp. SGJ using response surface methodology

Melanins are predominantly indolic polymers which are extensively synthesized in animals, plants and microorganisms. It has wide applications in cosmetics, agriculture and medicine. In the present study, optimization of process parameters influencing melanin production was attempted using the response surface methodology (RSM) from Brevundimonas sp. SGJ. A Plackett-Burman design was used for screening of critical components, while further optimization was carried out using the Box-Behnken design. The optimum conditions observed were pH 5.31, tryptone 1.440 g l⁻¹, L-tyrosine 1.872 g l⁻¹ and CuSO₄ 0.0366 g l⁻¹. Statistical analysis revealed that the model is significant with model F value 29.03 and R² value 0.9667. The optimization of process parameters using RSM resulted in a 3.05-fold increase in the yield of melanin. The intermittent addition of L-tyrosine enhanced the melanin yield to 6.811 g l⁻¹. The highest tyrosinase activity observed was 2,471 U mg⁻¹ at the 18th hour of the incubation period with dry cell weight of 0.711 g l⁻¹. The melanin production was confirmed by UV-Visible spectroscopy, FTIR and EPR analysis. Thus, Brevundimonas sp. SGJ has the potential to be a new source for the production of melanin.