The global proteomic response of the non-starter
lactic acid bacteria Lactobacillus casei strain GCRL163 under
carbohydrate depletion was investigated to understand aspects of its survival
following cessation of fermentation. The proteome of L. casei GCRL163
was analysed
quantitatively after growth in modified MRS (with and without Tween 80) with
different levels of lactose (0% lactose, starvation; 0.2% lactose, growth
limiting; 1% lactose, non-growth limited control) using gel-based and gel-free
proteomic analysis. Results revealed carbohydrate starvation lead to
suppression of lactose and galactose catabolic pathways as well as nucleotide and protein synthesis. Enzymes of
the glycolysis/gluconeogenesis pathway, amino acid synthesis, pyruvate metabolism,
and citrate metabolism became more abundant as well as other carbohydrate
catabolic pathways suggesting increased optimisation of intermediary metabolism
and scavenging. Tween 80 did not affect growth yield, however, proteins related
to fatty acid biosynthesis were repressed in the presence of Tween 80. The data
suggests that L. casei adeptly switches to a scavenging mode by
adjusting energetic requirements when carbohydrate starved and thus can sustain
survival for weeks to months. Explaining the adaptation of L. casei during
lactose starvation will assist efforts to maintain viability of L. casei
and extend its utility as a beneficial dietary adjunct.