Objective
This project relates to studies to improve the properties of industrial Bacillus and Lactobacillus strains for the production of high- and low-molecular weight compounds.
Bacteria impose regulatory mechanisms on metabolic processes in order to insure that the needs of the cell are met but not exceeded. These regulatory mechanisms interfere with the desired exhaustive industrial production of low and high- molecular weight compounds by bacteria, and with their use in food industry. The most important of these regulatory mechanisms is catabolite repression (CR) which controls carbon and nitrogen metabolism and carbon fluxes under conditions where rapidly metabolisable carbon sources are abundant. It is the aim of this project to exploit the knowledge that was gained in the previous BIOTECH programme, for the construction of novel strains of industrially important, food-grade Gram-positive bacteria that are insensitive to CR and deregulated at the enzyme level. Bacillus and Lactobacillus are chosen because they are the most important production organisms of our industrial partners.
The two main goals of this proposal are i) to unravel all signalling pathways triggering CR in bacilli and lactobacilli, and ii) to construct in a predetermined way improved production strains and to determine the optimal growth conditions for the corresponding production processes. The knowledge gained about the mechanism of CR will specifically be used to improve storage properties of fermented milks with L. casei of DANONE (postacidification), to improve the production of ß-glucanase by a Bacillus production strain used by COGNIS, to optimize the fermentation of pentose sugars by lactobacilli for soy production as well as to improve the nutritive value of feed, and to construct L. casei strains of DANONE in which C-fluxes important to milk fermentation and flavour production can be controlled.
The industrial importance of the proposal is underlined by the active participation of DANONE and by the support of COGNIS providing 200,000- DM for Bacillus strain improvement.