Enhanced melanin pigment production from Dietzia schimae NM3 in cheese whey using Box-Behnken design

Abstract

Melanin is a natural, dark-brown complex molecular structure pigment formed by the oxidative polymerization of phenolic compounds. Microbial melanin pigment can be use in industrial fields, canned additives and preservatives. Optimization method is used to produce a quick and sufficient product with reliable and cost-effective processes. In this project, four factors (temperature, l-tyrosine, pH and CuSO4) affecting in melanin production by Dietzia schimae NM3 were optimized by response surface methodology with Box–Behnken design in inexpensive medium (whey powder). The anti-bacterial activity of D. schimae melanin was assayed by disk diffusion test. The optimal medium compositions were obtained in whey 5% (w/v), l-tyrosine 2.5 g/l, CuSO4 0.013 g/l, pH 10.5, and temperature 32 °C by maximum yield of 790 mg/l melanin pigment. The ANOVA results of RSM showed a significant P-value (0.0001), model F-value (78.84) and probability R² (0.98), with insignificant lack of fit (0.091). Melanin also showed antibacterial activity against gram-positive strains such as Bacillus cereus (20 mm), B. subtilis (18 mm), Streptococcus pyogenes (17 mm), Staphylococcus epidermidis (18 mm), and S. aureus (18 mm), which was comparable with amoxicillin (AMX) and cefotaxime (CTX) as control positives. We realized the ability of D. schimae melanin pigment as natural substances to be considered for industrial fields due to its biocompatibility and physicochemical properties.