Waste to wonders: microbial cell factories for waste valorisation

<p dir="ltr">A rapidly rising population and the growth of industrialisation are causing increasing challenges due to the consumption of finite natural resources and the generation of wastes. However, precision fermentation by <i>Saccharomyces cerevisiae</i> presents a promising strategy for addressing both problems through the conversion of low-value waste substrates into high-value products. Two targets include starch and chitin, found in potato and crustacean wastes, respectively. This study explored the potential to express hydrolytic enzymes, both directed by their native signal peptide or a host-specific signal peptide, to process these waste polymers. Six recombinant <i>S. cerevisiae</i> strains for starch degradation and twelve strains for chitin degradation were developed in this work. While the use of a host-specific signal peptide was not found to consistently improve extracellular activity, the expression of recombinant amylases enabled three strains to grow on raw potato starch as a sole carbon source and the expression of recombinant chitinases enabled degradation of both colloidal and raw chitin. Ultimately, the findings from these two waste feedstock studies may help to address the issues of global waste pollution and make precision fermentation an economically viable process, creating a sustainable and circular bioeconomy.</p>