Production, physico-chemical characterization and antioxidant activity of natural melanin from submerged cultures of the mushroom Auricularia auricula

Melanin production was done using submerged cultures of the mushroom Auricularia auricula. It was found that 1% methanol, 0.25% peanut oil, 1.0% stearic acid or 0.5% palmitic acid were helpful for melanin bio-synthesis while Tween 80 significantly (p < 0.05) reduced the melanin formation. The inhibitory test and scanning electron microscopy analysis showed that the melanin consisted mostly of eumelanin with an amorphous structure. The melanin had strong antioxidant activity using the in vitro evaluation of its superoxide radical, 2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical and hydroxyl radical scavenging activity, and showed good stability at 100 °C for 5 h, natural light for 10 days, ultraviolet light for 4 h and with conventional food additives such as sugar. The results suggested that a submerged culture of A. auricula is an effective method to produce melanin, which could potentially be used as a natural antioxidant in the food, cosmetic and pharmaceutical industries.