Efficient Biofilm-Based Fermentation Strategies for L-Threonine Production by .

Biofilms provide cells favorable growth conditions, which have been exploited in industrial biotechnological processes. However, industrial application of the biofilm has not yet been reported in , one of the most important platform strains, though the biofilm has been extensively studied for pathogenic reasons. Here, we engineered by overexpressing the gene, which successfully enhanced its biofilm formation under industrial aerobic cultivation conditions. Subsequently, a biofilm-based immobilized fermentation strategy was developed. L-threonine production was increased from 10.5 to 14.1 g/L during batch fermentations and further to 17.5 g/L during continuous (repeated-batch) fermentations with enhanced productivities. Molecular basis for the enhanced biofilm formation and L-threonine biosynthesis was also studied by transcriptome analysis. This study goes beyond the conventional research focusing on pathogenic aspects of biofilm and represents a successful application case of engineered biofilm to industrial processes.