CO2 fixation in extreme conditions: native functioning and reengineering of the 3-hydroxypropionate/4-hydroxybutyrate cycle in Sulfolobus acidocaldarius

Both in society and industry, awareness is raised that a transition
from a petrochemical industry towards more sustainable bio-based
processes is urgent. In this context, the use of microorganisms with
autotrophic metabolism as cell factories for the direct conversion of
CO2 into high-added value chemicals or fuels is a promising
approach. Recently, a unique autotrophic CO2 fixation pathway was
discovered in thermoacidophilic archaea, growing optimally at
industrially relevant conditions of high temperature and low pH. While
the genetically amendable and industrially promising species
Sulfolobus acidocaldarius encodes the pathway genes, it has lost the
capability to fix CO2. Here, we will investigate the factors that have
caused this loss: either one or several of pathway enzymes are
dysfunctional, or the expression and transcriptional regulation of the
pathway is defect. Omics-methods will be combined with detailed
biochemical analyses to generate deep insights into the functioning
of the pathway. These insights will be used for the re-engineering of
CO2 fixation in S. acidocaldarius by restoring the identified defects,
followed by bioprocess engineering for pilot scale autotrophic growth.
This project aims to develop an efficient microbial CO2 fixation
process working in extreme conditions. Furthermore, fundamental
insights into the functioning of the 3-hydroxypropionate/4-
hydroxybutyrate cycle as well as in its transcriptional regulation will
be generated.