Selection of Medium and Optimization of Process Parameters for Melanin Biosynthesis from Pseudomonas stutzeri HMGM-7

Abstract

Oxidative polymerization of phenolic compounds and indolic compounds produces brown or black pigments called Melanins. In microbes, melanin production is generally related with various survival mechanisms. Some of the bacteria like Bacillus thuringiensis, Klebsiella sp., Proteus mirabilis, Pseudomonas aeruginosa, Pseudomonas stutzeri and Rhizobium sp. are reported to produce melanins. They have immense applications in the field of agriculture, cosmetics and pharmaceutical industries due to their photo-protective, UV protective and anti-oxidant activities. The objective of this study was to investigate the effects of different growth media and process parameters on melanin production. The marine bacterial strain Pseudomonas stutzeri HMGM-7 (MTCC 11712) was selected and the effect of different media such as Nutrient Broth (NB), Luria Bertini (LB) broth, Bushnell-Haas broth (BHB) and Trypticase Soy broth (TSB) and various medium components were investigated with a one factor at a time approach. Parameters like shaking frequency, inoculum age, inoculum size, pH and temperature were also investigated in order to obtain the optimum conditions for maximum melanin production. The highest yield of melanin concentration, 0.27 g/L, was obtained in nutrient broth at 32 h. The yield was 1.53 times higher than the melanin obtained before optimization, 0.177 g/L at 48 h. The increase in the productivity of melanin after selection of suitable medium and optimization of process parameters was 128.73 %.