The lack of extensive and standardized genetic parts and tools to control gene expression and as
such to predictably engineer species from all over the bacterial domain is a major bottleneck for
industrial biotechnology (IB). As a result, when selecting the preferred production host,
biotechnological engineers generally restrict themselves to well-known workhorses, such as E. coli
and S. cerevisiae. However, the choice for a non-optimal production host as starting point for
extensive engineering ultimately results in even longer development times and associated costs
due to, e.g., a problematic downstream processing. These issues can however largely be solved by
wisely selecting the preferred production hosts, making use of the enormous heterogeneity of the
bacterial domain. Therefore, the objective of this research proposal is the development of a crossbacterial
expression system (CBES) that can be used to regulate gene expression across bacterial
species. As such, this system would abolish the limitation to use well-known production hosts in IB
and allow to use product and process-adapted production hosts. This CBES will first be validated in
various bacterial hosts with appealing characteristics in view of IB application. Next, the industrial
relevance of the CBES will be put to the test by optimizing kaempferol production in C. necator
PHB-4, in view of its superior malonyl-CoA synthesis capacities, which is the main rate-limiting
precursor molecule.