1 SCIENTIFIC REPORTS | (2018) 8:14460 | DOI:10.1038/s41598-018-32854-9 www.nature.com/scientificreports Biosynthesis of organic photosensitizer Zn-porphyrin by diphtheria toxin repressor (DtxR)- mediated global upregulation of engineered heme biosynthesis pathway in Corynebacterium glutamicum Young Jin Ko 1 , Young-Chul Joo 1 , Jeong Eun Hyeon 1 , Eunhye Lee 1 , Myeong-Eun Lee 1 , Jiho Seok 1 , Seung Wook Kim 2 , Chulhwan Park 3 & Sung Ok Han 1 Zn-porphyrin is a promising organic photosensitizer in various felds including solar cells, interface and biomedical research, but the biosynthesis study has been limited, probably due to the difculty of understanding complex biosynthesis pathways. In this study, we developed a Corynebacterium glutamicum platform strain for the biosynthesis of Zn-coproporphyrin III (Zn-CP III), in which the heme biosynthesis pathway was efciently upregulated. The pathway was activated and reinforced by strong promoter-induced expression of hemA M (encoding mutated glutamyl-tRNA reductase) and hemL (encoding glutamate-1-semialdehyde aminotransferase) genes. This engineered strain produced 33.54 ± 3.44 mg/l of Zn-CP III, while the control strain produced none. For efcient global regulation of the complex pathway, the dtxR gene encoding the transcriptional regulator diphtheria toxin repressor (DtxR) was frst overexpressed in C. glutamicum with hemA M and hemL genes, and its combinatorial expression was improved by using efective genetic tools. This engineered strain biosynthesized 68.31 ± 2.15 mg/l of Zn-CP III. Finally, fed-batch fermentation allowed for the production of 132.09 mg/l of Zn-CP III. This titer represents the highest in bacterial production of Zn-CP III reported to date, to our knowledge. This study demonstrates that engineered C. glutamicum can be a robust biotechnological model for the production of photosensitizer Zn-porphyrin. Porphyrins functioning as photo-electrochemical materials are of particular interest in a range of areas related to solar cell technology, battery chemistry, solid/liquid interfaces and biomedical research because of their func- tional and structural properties that incorporate a metal ion in the center and have great absorption bands in the visible spectrum 1–7 . In particular, Zn-porphyrin derivatives have recently attracted much attention for their great potential application as a promising raw material for sensitizing an organic solar cell in a photovoltaic system that harvests light to convert solar energy into electricity, or in catalyzing multistep reactions at interface 3,4,8–13 . In addition to electronic and physicochemical applications, Zn-porphyrins have been studied as photosensitiz- ers for their antitumor and antibacterial activity in photodynamic therapy-mediated biomedical applications 14 . Furthermore, iron-porphyrin has been used to synthesize bio-based magneto-electric nanocrystals by the heme polymerase enzyme complex and demonstrated as a monomer for advanced nanomaterial synthesis 15 . Most 1 Department of Biotechnology, Korea University, Seoul, 02841, Republic of Korea. 2 Department of Chemical and Biological Engineering, Korea University, Seoul, 02841, Republic of Korea. 3 Department of Chemical Engineering, Kwangwoon University, Seoul, 01897, Republic of Korea. Correspondence and requests for materials should be addressed to S.O.H. (email: samhan@korea.ac.kr) Received: 8 June 2018 Accepted: 14 September 2018 Published: xx xx xxxx OPEN