Monitoring rhodotorula glutinis CCMI 145 stress physiological response during fed-batch fermentations using multi-parameter flow cytometry

摘要

Multi-parameter flow cytometry was used to monitor R. glutinis stress response during a fed-batch fermentation, through cell viability, lipid content and intrinsic light scatter. During the yeast fermentation, the proportion of cells with permeabilized membrane (dead cells) increased when nutrients and/or oxygen became limiting. Yeast cells showed a higher injury level when grown under other nutrient limitation than under oxygen limiting conditions, as the dead cells reduced their internal content and size in the former situation, suggesting drastic cells lysis. The maximum yeast lipid content was 8% (w/w) at t=38.3 h. Such low lipid content was attributed to oxygen limitation, which highlights the importance of the oxygen transfer rate when producing lipids from aerobic yeast cultures. Changes in Forward and Side scatter light signals were detected during the yeast growth, which can provide a useful and fast way to identify the yeast growth phase. The multi-parameter approach here reported represents a better control system based at the individual cell level that can be used for optimization of yeast bioprocess performance, and may also be used for quick screening of yeast strains for single cell oil production.