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Abstract:
This study aimed to overproduce industrially relevant and safe bio-compound trans-cinnamic acid (tCA) from Photorhabdus luminescens with deletion strategies and homologous expression strategies that had not been applied before for tCA production.The overproduction of the industrially relevant compound tCA was successfully performed in Photorhabdus luminescens by deleting stlB (TTO1ΔstlB) encoding a cinnamic acid CoA ligase in the isopropylstilbene pathway and the hcaE insertion (knockout) mutation (hcaE:: cat) in the phenylpropionate catabolic pathway, responsible for tCA degradation. A double mutant of both stlB deletion and hcaE insertion mutation (TTO1DM ΔstlB-hcaE:: cat) was also generated. These deletion strategies and the phenylalanine ammonium lyase-producing (PI-PAL from Photorhabdus luminescens) plasmid, pBAD30C, carrying stlA (homologous expression mutants) are utilized together in the same strain using different media, a variety of cultivation conditions, and efficient anion exchange resin (Amberlite IRA402) for enhanced tCA synthesis. At the end of the 120-hour shake flask cultivation, the maximum tCA production was recorded as 1281 mg L−1 in the TTO1pBAD30C mutant cultivated in TB medium, with the IRA402 resin keeping 793 mg L−1 and the remaining 488 mg L−1 found in the supernatant.tCA production was successfully achieved with homologous expression, coupled with deletion and insertion strategies. 1281 mg L−1is the highest tCA concentration that achieved by bacterial tCA production in flask cultivation, according to our knowledge. IRA402 resin adsorbers seem useful for enhancing tCA acquisition in bacterial cultures. Mutations on the hcaE and stlB genes clearly increased the amount of tCA. P. luminescens is an effective bacterial candidate to produce tCA in industrial applications with the implemented strategies.
