Fig. 2

KA production in A. niger cell factory overexpressing kojA from A. oryzae. a Illustration of the genetic organization for the kojA overexpression cassette in pLH1081. b Expression levels of kojA in the parent strain S834 and kojA overexpression strain S1991 respectively. The transcriptional levels in each strain at 5 d and 7d after inoculation are indicated. All experiments measuring transcription via qRT-PCR were normalized using the actin gene as a housekeeping control. c KA can form a red chelated compound with ferric ions. Color reaction of 5 day culture of S1991 with ferric ions indicates the kojic acid secretion by strain S1991. Similar results were obtained by HPLC using the commercial KA as standard. d The amount of KA produced by A. niger S1991 in shake flasks for 5 days and 7 days was determined by HPLC. Commercial kojic acid was used as a standard