Identification, biological evaluation, and improved biotransformation of a phenazine antioxidant using Streptomyces lomondensis S015 whole cells

Abstract

Natural phenazines are important secondary metabolites that generally exhibit broad antimicrobial bioactivities. However, the bioactivity diversity of phenazines is relatively narrow due to the limited substitution of side groups. In this study, Streptomyces lomondensis S015 was confirmed with capability of catalyzing phenazine-1-carboxylic acid (PCA) to 5-(2-hydroxyacetyl)− 5,10-dihydrophenazine-1-carboxylic acid (HDPCA) based on substrate feeding, UPLC-MS and NMR analysis. Besides antimicrobial activity, HDPCA exhibited potent antioxidant activity compared with PCA and the antioxidant butylated hydroxytoluene (BHT). Furthermore, an efficient whole cells biotransformation system was developed by screening carbon sources and optimizing reaction conditions. Using S. lomondensis S015 cells prepared from glucose as the biocatalyst, the production of HDPCA achieved 1.38 mM (392.0 mg/L) under a rotation rate of 220 rpm, 32 °C, pH 7.0, and 3.6 g/L dry cell weight for 36 h. This work not only identified the intriguing bioactivity of HDPCA but provide an environmentally friendly strategy for the biocatalysis of phenazines.