Metabolism associated with raised metabolic flux t

Authors: A D Welman I S Maddox R H Archer

Publish Date: 2006/02/02

Volume: 33, Issue: 5, Pages: 391-

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Abstract

Exopolysaccharide EPS metabolism was studied in a galactosenegative strain of Lactobacillus delbrueckii subsp bulgaricus using two different approaches Firstly using both the parent strain and a chemically induced mutant with higher yield and specific productivity of EPS than the parent comparative information was obtained relating to enzyme activities and metabolite levels associated with EPS formation when grown on lactose Under continuous culture conditions D=010 h−1 the higher metabolic flux towards EPS formation in the mutant strain relative to the parent appeared to be mediated by raised levels of UDPglucose pyrophosphorylase UGP Marginally raised UDPgalactose 4epimerase UGE activity in the mutant strain suggested that this enzyme could also play a role in EPS overproduction The second approach involved investigating the effect of growth rate on sugar nucleotide metabolism in the parent as it is known that EPS production is growthassociated in this strain UGE activity in the parent strain appeared to increase when the growth rate was elevated from 005 to 010 h−1 and further to 035 h−1 conditions that can be associated with higher levels of metabolic flux to EPS formation Concurrent with these increments intracellular ATP levels in the cell were raised In both investigations glucose6phosphate accumulated pointing to a constriction at this branchpoint and a limitation in the flow of carbon towards fructose6phosphate or glucose1phosphate The changes in metabolism associated with enhanced flux to EPS provide guidance as to how the yield of Lactobacillus delbrueckii subsp bulgaricus EPS can be improved

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