Insights into the ecophysiology and biophysics of microbes involved in fermentation
Bramley apple microflora was shown to consist of Aspergillus, Cladosporium, Fusarium, Penicillium and other fungi. Some of these fungi were used for studies to determine biophysical activities of key cellular stressors present during cider fermentations: sugars, ethanol, and glycerol. Generally, these compounds acted as stressors, but glycerol was found to enhance metabolic activity and cell division at low water activity. Paradoxically, however, glycerol also exerted chaotropic activity when present at high concentrations and this ultimately limited the biotic activity of fungi, regardless of species, as assessed by studies of differentiation and cell division during germination. Other studies, based on comparisons between these fungi, the cider yeast Saccharomyces cerevisiae, and several species of bacteria indicate that the microbial lag phase, which is often regarded as an indicator of cellular stress, is in reality often inconsistent with the level of stress. The work carried out here also produced a novel assay in which to investigate the effect glycerol has on the survivability of microbes in highly stressful conditions and provided novel insights, which are pertinent to the wider microbiology field. For instance, the work provided evidence that cellular metabolism, differentiation, and cell division can occur below the previous water activity window of life. Thesis is embargoed until 31 July 2026.
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