Modulation of CO2 utilization by Cupriavidus necator H16 for high value chemical production
Lead Research Organisation:
University of Nottingham
Department Name: School of Life Sciences
Abstract
CO2 assimilation in R. eutropha, is mediated by Calvin-Benson-Bassham (CBB) cycle encoded by two almost identical cbb operons, one located on the pHG1 megaplasmid and the other on chromosome 2 (Pohlmann et al., 2006). The effective expression of these operons, and in particular the genes encoding the major rate-limiting enzyme, ribulose 1,5-bisphosphate carboxylase/ oxygenase (RubisCO), are crucial. Both operons and are tightly regulated by the cbbR transcriptional activator located at the 5' end of the chromosomal copy of the cbb operon (Kusian and Bowien, 1995). This LysR-type regulatory protein con-trols the expression of the cbb operons by binding to their identical promoter sequences (Dangel and Tabita, 2015). LysR independent, and preferably constitutive transcription of the cbb operon might prove advantageous for enhancing the efficiency of CO2 fixation efficiency of the CBB cycle. To further improve the endogenous CO2 assimilation pathway we bring about the controllable expression of synthetic DNA modules encoding functional carboxysomes for the co-localisation of CAs and RuBisCO molecules with improved CO2-capture capabilities.
Organisations
People |
ORCID iD |
| Jeremy Roberts (Primary Supervisor) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| BB/M008770/1 | 01/10/2015 | 31/10/2024 | |||
| 1804149 | Studentship | BB/M008770/1 | 01/10/2016 | 25/11/2020 |
| Description | During the time span of the award, several strategies to implement carbon fixation in the chassis organism C.necator were explored. One strategy involving the replacement of a down-regulation system (CbbR) and substitution with either a constitutive promoter or inducible promoter proved to be not very successful. The strains after engineering were not able anymore to grow in autotrophic conditions as well as the wild type. Another strategy involving the engineering of the cbb operon repressor protein CbbR, would allow the strains to continuously fix CO2 opening the way for co-consumption experiments with VFAs and CO2. This is relevant in the current economy because it could allow the use of the C.necator strains in the down-stream process for solid waste treatment. In fact, during anaerobic fermentation of solid waste, VFAs and CO2 are produced and at the moment realised in the atmosphere. While the energy embedded in the molecule could be used for the production of bioplastic. The third strategy involving the expression of heterologous carbon concentrating organelles (called carboxysomes) in the chassis organism C.necator suggested the ability of the latter to complement growth in autotrophic conditions of the RubisCO deficient C.nec strains. But, with no improvement in biomass accumulation was observed. |
| Exploitation Route | The outcomes outline the difficulties in establishing an economically viable and efficient method for bioplastic production. Hack the bottleneck of carbon fixation has proved very difficult and not totally successful. Coupling bioplastic production with waste treatment could be a viable way of reducing the impact of the cost. Further research on the co-consumption of organic compounds and CO2 should be carried on in the near future to consolidate the preliminary experimental data collected during the award. |
| Sectors | Agriculture, Food and Drink,Chemicals,Energy |