To investigate the outcomes of capsule lost on cell transformation efficiency and chemicals (1,3-propanediol, 2,3-butanediol, and 2-ketogluconic acid) production by Klebsiella pneumoniae. The cps gene cluster showed low sequence homology with pathogenic strains. The wza is a highly conserved gene in the cps cluster that encodes an outer membrane protein. A non-capsulated mutant was constructed by deletion of wza. Phenotype studies demonstrated that non-capsulated cells were less buoyant and easy to sediment. The transformation efficiency of the non-capsulated mutant reached 6.4 x 10(5) CFU mu g(-1) DNA, which is 10 times higher than that of the wild strain. 52.2 g 1,3-propanediol L-1, 30.7 g 2,3-butanediol L-1, and 175.9 g 2-ketogluconic acid L-1 were produced by non-capsulated mutants, which were 10-40% lower compared to wild strain. Furthermore, viscosities of the three fermentation broths decreased to approximately 1.3 cP from the range of 1.8-2.2 cP. Non-capsulated K. pneumoniae mutants should allay concerns regarding biological safety, improve transformation efficiency, lower viscosity, and subsequently ameliorate the financial burden of the downstream process of chemicals production.