The challenge of fermenting solids

Prof. Teresa Gea Leiva (Universitat Autònoma de Barcelona)

The development of the circular bioeconomy claims for the change of paradigm from wastes to resources. Efforts are devoted to unravelling the huge potential of organic solid wastes as feedstock for bioconversion processes. Solid-state fermentation is approached as a promising technology for that purpose.

Several works describe de production of bioproducts (a long list including enzymes, biosurfactants or biopesticides) from a broad range of organics. Still, this technology presents limitations yet to overcome, linked to the physical and microbiological phenomena and the intrinsic nature of the organic solids.

This presentation will overview the current challenges and implications for the industrial development of solid-state fermentation.

Uncoupling of growth and product formation in Saccharomyces cerevisiae

Dr. Walter van Gulik (TU Delft)

Over the past 15 years his group has used the yeast S. cerevisiae as a model microorganism to study its physiology at near-zero growth rates. To this end retentostat cultures were carried out were the growth was restricted by limited supply of the carbon and energy source glucose.

Successful uncoupling of growth and production was achieved, whereby the cells remained in a very robust and metabolically active state. Recently the zero-growth concept was developed further to investigate industrial application, thereby using production of the non-catabolic product succinic acid in non-energy limited retentostat cultures as model system. The main aim was to improve our understanding of the physiology of yeast at near-zero growth rates under harsh industrial conditions (high CO₂ level and low pH), thereby providing insights for the design of industrial fermentation processes based on the near-zero growth concept.