Novel and improved yeast cell factories for biosustainable processes

The utilization of an increasingly diverse range of cheap waste substrates will be an ongoing challenge for the bio-based economy, where the mobilization of nutrients from a variety of waste products will be necessary for realization of biosustainability on an industrial scale. Bioprocesses utilizing traditionally applied cell factories are generally based on a limited range of substrates (mainly glucose). However, a wider diversity in substrate range is highly desirable in developing biorefinery scenarios where feed-stocks containing a number of carbon sources are typically employed. In addition to plant biomass hydrolysates, glycerol is of interest here, being available in amounts relevant for industrial scale bioprocesses due to increased production of biodiesel. The well characterised cell factory Saccharomyces cerevisiae exhibits a clear preference for glucose as a carbon source, and is highly adapted to its utilisation. Although there have been several studies on glycerol metabolism in S. cerevisiae, many industrially used strains grow poorly on glycerol (μmax = 0.01h-1). On the other hand, several non-conventional yeast species are efficient in utilization of glycerol, some with relevant applications as cell factories (including Pichia spp. and Yarrowia lipolytica) and other less well characterized strains (e.g. Pachysolen tannophilus). This presentation will address how we evaluate cellular performance with a view to utilizing yeast species in industrial biotechnology applications. In addition, strategies for optimizing cellular performance based on either process engineering principles or genetic engineering will be presented. The work focusses on alternative substrates to glucose, the extension of substrate range in S. cerevisiae and an evaluation of nonconventional yeast species for industrial biotechnology applications.