Klebsiella spp as a 1, 3-propanediol producer: the metabolic engineering approach

Klebsiella spp are one of the best natural producers of 1,3-propanediol (1,3-PD). However, their usage in the biotechnological production of the diol is limited, since the species belong to the second hazard group. Nevertheless, multiple advantageous traits of Klebsiella spp justify the international effort devoted to develop a biotechnological process of 1,3-PD production with these microorganisms. Apart from the process engineering approach aiming at improvement of 1,3-PD production by Klebsiella spp, plethora of metabolic engineering approaches have been reported. Different strategies have been undertaken to genetically improve Klebsiella strains and provide them with the ability to synthesize 1,3-PD more efficiently. These include over-expression of both homologous and heterologous genes of the 1,3-PD synthesis pathway, protein and cofactor engineering, deletion of the genes involved in by-products formation. This review provides an overview of the initial and most recent reports on the metabolic engineering of Klebsiella spp with the aim of improvement of 1,3-PD biosynthesis.