Melanin biopolymers from newly isolated Pseudomonas koreensis strain UIS 19 with potential for cosmetics application, and optimization on molasses waste medium.

AIMS

Bacterial melanins are UV-absorber biopolymers with potential applications in cosmetics and pharmaceutical industries. However, the cost concern of these pigments remains a limiting factor for their commercial production. Hence, the present study was aimed to isolate a bacterium with high yield of melanin by optimization of an inexpensive waste sources.

METHODS AND RESULTS

Pseudomonas koreensis UIS 19 (accession number: MG548583), which displayed significant bioproduction of melanin along with high tyrosinase enzyme activity was isolated from soil and introduced as a melanin-producing bacterium. Scanning and transmission electron microscope studies revealed that melanin pigments accumulated inside as well as the extracellular space of the cells. Melanin was extracted from the isolated strain and its detection was investigated using NMR and HPLC analyses. Here, we showed that the DPPH radical scavenging activity of 20 mg ml melanin extracted from the isolated strain was >92·42% and its sun protection factor (SPF) value was 61·55. Melanin production by the UIS 19 in molasses medium showed sugar consumption (32 g l ) for biomass production (5·4 g dry wt) and melanin yield of 0·44 g dry wt g biomass from l-tyrosine. Some critical intermediated such tyramine, l-dopa, dopamine and dopaquinone related to the melanin Raper Mason pathway were detected by H-NMR. Furthermore, to achieve high bioproduction of melanin in inexpensive media include 5% molasses 5 Brix as an industrial waste, nutritional and environmental parameters were screened using response surface methodology by Box-Behnken design in which, maximum melanin yield of 5·5 g dry wt l was obtained.

CONCLUSIONS

The bioproduction of melanin as valuable compound from P. koreensis was performed using an optimized waste medium. The purified melanin showed high radical scavenging activity and high SPF value.

SIGNIFICANCE AND IMPACT OF THE STUDY

Pseudomonas koreensis UIS 19 is a promising candidate for industrial production of melanin as cosmetic skin-care product.