Optimization, a Potential Production, GC-MS and Characterization of Dark Green Pigment from New Local Isolate Streptomyces nigra Strain GH12

Abstract

Due to increasing health awareness among consumers and the identification of novel pharmacological properties of diverse natural pigments, the market for natural pigments is currently seeing rapid growth. Streptomyces. nigra GH12, a new Actinomycete isolate identified by 16S rRNA used for dark green pigment production. Manipulations of the factors affecting pigment production are the most effective way to have maximum yield of pigment. Starch 2.5% (w/v), ammonium nitrate 0.2% (w/v), dibasic sodium phosphate 0.1% (w/v), inoculums size 6% (v/v),  initial pH level of 8, 150 rpm rotation speed, 37 ºC temperature, and 9 days of incubation  were found the optimum growth conditions for the highest green  pigment production. The extraction of green pigment was performed efficiently with ethanol solvent. Results showed no effect on the pigment content at 40, 50 and 60°C. On heating pigment extract at 70, 80, 90 and 100oC for 60 min, retention of pigment remained as high as 97.4, 93, 86 and 79% of the total pigment density , respectively, even with continuous treatment at 100°C for more 60 min. The results indicated that the pigment extracts exhibited their greatest stabilities at high pH values, i.e. 8.0, 8.5, 9.0 and 10.0, during the entire holding time. The pigment was characterized by full UV-visible spectroscopic screening, where the potential absorption maximum of the target green pigment extract was recorded in the range of 300 ̶ 360 nm, with a λmax at 340 nm. Moreover, the chemical composition diversity of the pigment extract was further investigated by GC/MS analysis that revealed the presence of 57 metabolites in their silylated form.