Fig. 4

Screening of the CvPHBH random mutant library using the laccase-mediated colorimetric method. A Schematic representation of the laccase-catalyzed oxidative dimerization of 4-amino-3-hydroxybenzoic acid (4,3-AHBA) to 2-aminophenoxazin-3-one-7-carboxylic acid (2,3,7-APOC). B The absorption spectrum of an orange-yellow reaction solution after mixing laccase and 4,3-AHBA in 100 mM citrate buffer (pH 4.5). C The results of HPLC analysis of the culture supernatants of Corynebacterium glutamicum strains expressing the CvPHBH mutants found using the random mutagenesis screening. White and gray colored bars indicate the concentration of 4-aminobenzoic acid (4-ABA) and 4,3-AHBA, respectively. Data are represented as mean ± standard deviation of biological replicates (n = 6). Yellow circles indicate the mean percentage of 4,3-AHBA. The horizontal axis indicates the strains of interest expressing CvPHBH mutants. WT: wild type