Application of CRISPRi for prokaryotic metabolic engineering involving multiple genes, a case study: Controllable P(3HB-co-4HB) biosynthesis

Clustered regularly interspaced short palindromic repeats interference (CRISPRi) is used to edit eukaiNotic genomes. Here, we show that CRISPRi can also be used for fine-tuning prokaryotic gene expression while simultaneously regulating multiple essential gene expression with less labor and time consumption. As a case study, CRISPRi was used to control polyhydroxyalkanoate (PHA) biosynthesis pathway flux and to adjust PHA composition. A pathway was constructed in Escherichia coil for the production of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] from glucose. The native gene sad encoding E. coli succinate semi-aldehyde dehyclrogenase was expressed under the control of CRISPRi using five specially designed single guide RNAs (sgRNAs) for regulating carbon flux to 4-hyclroxybutyrate (4HB) biosynthesis. The system allowed formation of P(3HB-co-4HB) consisting of 1-9 mol% 4HB. Additionally, succinate, generated by succinyl-coA synthetase and succinate dehydrogenase (respectively encoded by genes sucC, sucD and scihil, sdhB) was channeled preferentially to the 4HB precursor by using selected sgRNAs such as sucC2, sucD2, sclhB2 and sclhAl via CRISPRi. The resulting 4HB content in P(3HB-co-4HB) was found to range from 14 to 18.4 mol% depending on the expression levels of down-regulated genes. The results show that CRISPRi is a feasible method to simultaneously manipulate multiple genes in E. coll. (C) 2015 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.