Exploring and engineering formaldehyde assimilation Increasing concerns regarding the environmental impact of our chemical production have shifted attention towards possibilities for sustainable biotechnology. One carbon (C1) compounds including methane methanol formate and CO are promising feedstocks for future bioindustry. CO2 is another interesting feedstock as it can also be transformed using renewable energy to other C1 feedstocks for use. While formaldehyde is not suitable as a feedstock due to its high toxicity it is a central intermediate in the process of C1 assimilation. This thesis explores formaldehyde metabolism and aims to engineer formaldehyde assimilation in the model organism Escherichia coli for the future C1 based bioindustry. The first chapter of the thesis aims to establish growth of E. coli on formaldehyde via the most efficient naturally occurring route the ribulose monophosphate pathway. Linear variants of the pathway were constructed in multiple gene knockouts strains coupling E. coli growth to the activities of the key enzymes of the pathway. ...