Many recombinant bacteria for hyaluronan (HA) production have been reported during the last
years. They exhibit significant advantages when compared to extraction of HA from animal
tissues or fermentation of pathogenic bacteria. Less organic solvents are required the host
organisms are not toxic and do not degrade HA and there is no need for extensive
downstream-processing. Nevertheless all these catalytic systems share one significant
limitation: a low molecular weight (MW). As a high MW is of great importance it is desirable
to establish an industrially feasible production process for this field. Therefore the aim of
this study was the development of a recombinant microbe to produce HA with a MW of 2 MDa and
more. Two strategies were followed: 1. Saccharomyces cerevisiae is a well-established
industrial workhorse and genetic tools are widely available. Using S. cerevisiae as production
host allows the investigation of HA synthases originating from higher eukaryotes the
expression of which might be quite complicated using a prokaryotic host. Also a lot is known
about the physiology of S. cerevisiae which will simplify manipulation of its genome by
deleting undesired pathways and integrating new genes. A synthetic pathway for precursor supply
will further facilitate HA synthesis. 2. Different Streptococcus species are known to produce
HA of different MW. As the determinants for the MW of HA have not yet been fully elucidated a
closer look will also be taken at several streptococcal synthases to see whether sequence
differences result in MW differences. Two new streptococcal HA synthases from Streptococcus
parauberis and Streptococcus iniae were also included. Moreover it was investigated how the
synthases behave under HA production conditions in recombinant Lactococcus lactis and whether
that performance differs in vitro.
