Heterologous expression of glutamyl-tRNA reductase gene in Rhodobacter sphaeroides O.U.001 to enhance 5-aminolevulinic acid production

Abstract

The pathways for synthesis of 5-aminolevulinic acid (5-ALA) use either succinyl-CoA and glycine (C-4 pathway), or glutamate (C-5 pathway). Although Rhodobacter sphaeroides synthesizes 5-ALA through the C-4 pathway, it also has the genes coding for the enzymes of the C-5 pathway, except for glutamyl-tRNA reductase. The glutamyl-tRNA reductase gene was cloned from Rhodospirillum rubrum and expressed in R. sphaeroides; thus, the C-5 pathway was enabled to function upon assembling all the required genes. Consequently, a new and unique bacterial strain producing more 5-ALA was developed. Biohydrogen was also produced in the same bioprocess within a biorefinery approach using sugar beet molasses as substrate. The amount of 5-ALA produced by the modified strain was 25.9 mg/g dry cell weight (DCW), whereas the wild-type strain produced 12.4 mg/g DCW. In addition, the amount of H₂ generated by the modified and wild-type cells, respectively, was 0.92 L/L culture and 1.05 L/L culture.

Keywords:

• aminolevulinic acid
• biohydrogen
• glutamyl-tRNA reductase
• heterologous expression
• Rhodobacter sphaeroides O.U.001

Acknowledgements

We thank Prof. Dr Richard R. Burgess (University of Wisconsin–Madison) for his valuable comments and corrections.

Additional information

Funding

This work was supported by The Scientific and Technological Research Council of Turkey [grant number 111T523].