Capturing and Characterising Wild Yeast for Beer Brewing

Abstract

Beer is typically made using fermentation with Saccharomyces cerevisiae or Saccharomyces pastorianus, domesticated brewing yeasts. Historically, wild, non-Saccharomyces yeasts have also been frequently used in mixed culture fermentations to provide interesting and unique flavours to beer. However, brewing using mixed cultures or by spontaneous fermentation makes reproducing flavours and beer styles extremely difficult. Here, we describe a pipeline from collection of wild yeast from plant material to the characterisation and industrial scale production of beer using wild yeast. We isolated and identified wild yeast strains from the St Lucia campus of The University of Queensland, Brisbane, Australia. Several isolates fermented efficiently at laboratory scale, but failed to grow at industrial scale due to the combination of maltose and pressure stress. Systems biology showed that the synergistic metabolic defects caused by these dual stresses converged on amino acid nutrient uptake. Glucoamylase addition relieved maltose stress and allowed industrial scale fermentation using wild yeast. Our workflow allows efficient collection and characterisation of diverse wild yeast isolates, identification of interventions to allow their use at industrial scale, and investigation of the genetic and metabolic diversity of wild yeasts.