Constitutive expression of RyhB regulates the heme biosynthesis pathway and increases the 5-aminolevulinic acid accumulation in Escherichia coli

In the current study, the small RNA ryhB, which regulates the metabolism of iron in Escherichia coli, was constitutively expressed in engineered E.coli DALA. The resulting strain E.coli DALRA produced 16% more 5-aminolevulinic acid (ALA) than the parent strain E.coli DALA in batch fermentation. Meanwhile, we found that addition of iron in the medium increased heme formation and reduced ALA yield, whereas the presence of iron chelator in the medium decreased heme concentration and increased the ALA production efficiency (ALA yield per OD600). The qRT-PCR analysis showed that the mRNA levels of hemB and hemH were also decreased as well as the known RyhB target genes of acnAB, sdhAB, fumA, and cydAB in E.coli DALRA. These results indicated that small RNA can be used as a tool for regulating ALA accumulation in E.coli.