Fig. 1.

The ‘forward’ metabolic engineering and ‘reverse’ metabolic engineering cycles and their interaction. In forward metabolic engineering, analysis of strains constructed based on rational design often results in scientific questions that need to be addressed by further analysis and consultation of the rapidly expanding knowledge on microbial metabolism and its regulation. In reverse metabolic engineering, generation and analysis of biodiversity – obviously, with special attention for strains that show improved performance – contributes to accelerated strain improvement and knowledge development (After Nielsen, 2001; Bailey et al., 1996; Bro & Nielsen, 2004).