Fig. 5

The effects of combined mutation of four negative regulator encoding genes on the kojic acid production. a. Colony Phenotype of four mutant strains grown on PDA for 3 days. The strains are listed as follows: the marker-less nrkC deletion mutant: S2743 (ΔnrkC), nrkC and nrkD double deletion mutant: S2683 (ΔnrkC, ΔnrkD), nrkC and nrkD double deletion mutant with RNAi targeting nrkA: S3058 (RNAi-nrkA, ΔnrkC, ΔnrkD), nrkC and nrkD double deletion mutant with RNAi targeting nrkA and nrkB: S3119 (RNAi-nrkA, RNAi-nrkB, ΔnrkC, ΔnrkD). All the four strains have the same genetic background of kojA overexpression except the genetic difference mentioned above. b KA production by the four engineered strains. The strains are listed as described above. The titers of KA produced by the four engineered strains in shake flask cultivations for 5 days and 7 days were shown