Caracterização de pigmentos escuros tipo melanina produzidas por bactérias isoladas de milho

Abstract

The melanin has a varied industrial application being of great use in the area of cosmetics, due to its excellent ability to absorb ultraviolet light (UV). Bacterial synthesis of melanin pigments is an alternative for scale production. In this research, 17 bacteria isolated from maize plants were used and evaluated for the production capacity of dark pigments. These were tested by inoculation in potato medium supplemented with L-tryptophan (5 mmol L-1) or with L-tyrosine (5 mmol L-1). Bacteria were then cultured and evaluated for the production of dark pigments. Four isolates (MT29, MT34, MT41 and MT70) were selected with higher production. The pigments were extracted and analyzed by UV-visible absorption spectrophotometry, infrared (IR) absorption spectroscopy and scanning electron microscopy (SEM). The MT70 isolate was considered the most promising because of its quantitative production. From the obtained data it was possible to detect differences in the IV profiles between the reference bacterium HM053 and the tested isolates. According to the SEM analysis the pigments are amorphous and with different dimensions and thicknesses. Only MT29 showed crystals in the shape of needles. The pigments showed cellular protection activity against UV rays and low antioxidant activity against the DPPH radical in 30 minutes. Thus, the dark pigments studied from the four bacteria associated with corn plants grown in the Cerrado of Goiás can be considered related to melanin because of its properties and characteristics.