A dive into yeast’s sugar diet – Comparing the metabolic response of
glucose, fructose, sucrose & maltose under dynamic feast/famine
conditions
Abstract
Scale-up of microbial bioprocesses to production scale is accompanied by
significant changes in growth conditions. One aspect are rapidly
changing substrate concentrations due to prolonged mixing times. The
impact of substrate gradients on the physiology of Saccharomyces
cerevisiae has been studied for glucose but no other industrially
relevant carbohydrate. With different transport mechanism, non-glucose
sugars will lead to a different intracellular response. Here we studied
the response of S. cerevisiae to gradients for four different
sugars: glucose, fructose, sucrose and maltose. To study the impact of
the carbon sources as well as the large-scale gradients, steady-state
and dynamic feast/famine cultivation conditions were applied. The
physiology, intracellular metabolome as well as the proteome were
compared. Especially, gradients of maltose lead to a significant
decrease in biomass yield. Under dynamic glucose, fructose and sucrose
conditions S. cerevisiae was able to maintain the biomass yield
of steady-state conditions. Although the physiology was very comparable
for these sugars, the intracellular metabolome and proteome changed. The
concentration of upper glycolytic enzymes decreased for glucose and
maltose (up to -60% and -40% respectively), while an increase was
observed for sucrose and fructose when exposed to gradients. At the same
time, enzymes of lower glycolysis were increased. Interestingly, common
stress-related proteins were decreased during dynamic conditions. The
observed adaptations to repeating gradients highlight the importance to
study physiology and metabolism under dynamic conditions to obtain
results that are relevant for the envisioned large-scale process.