Enhanced Production of 2-Hydroxyphenazine from Glycerol by a Two-Stage Fermentation Strategy in Pseudomonas chlororaphis GP72AN.

2-Hydroxyphenazine (2-OH-PHZ) is an effective biocontrol antibiotic secreted by Pseudomonas chlororaphis GP72AN and is transformed from phenazine-1-carboxylic acid (PCA). PCA is the main component of the recently registered biopesticide "Shenqinmycin". Previous research showed that 2-OH-PHZ was better in controlling wheat take-all disease than PCA; however, 2-OH-PHZ production was low under natural conditions. Herein, we confirmed that PCA induced reactive oxygen species in its host P. chlororaphis GP72AN and that the addition of DTT improved PCA production by 1.8-fold, whereas the supplementation of K3[Fe(CN)6] and H2O2 increased the conversion rate of PCA to 2-OH-PHZ. Finally, a two-stage fermentation strategy combining the addition of DTT at 12 h and H2O2 at 24 h enhanced 2-OH-PHZ production. Taken together, the two-stage fermentation strategy was designed to enhance 2-OH-PHZ production for the first time, and it provided a valuable reference for the fermentation of other antibiotics.