Induced Mutation Of Strain Producing 1,3-Propanediol By Plasma

Poly-Trimethylene Terephthalate (PPT) has numerous promising properties and applications. As a pivotal monomer to the synthesis of PTT, 1,3-propanediol (1,3-PD) has attracted particular attention of many famous corporation in the world in these years. Compared with chemical synthesis, microbial fermentations of 1,3-PD have many obvious advantages, including the environmental friendship and price advantage, and thus become the focuses of research. The inhibition of products on microorganism cells will limit the product titer and the yield of 1,3-PD on glycerol, and thus lead the product recovery and purification to a troublesome task. These problems may be effectively solved if some mutants with tolerance to high concentration of 1,3-PD and less byproducts were obtained by selective breeding.In this study an induced mutation technology by plasma combining thrice concentrating and replica screening is established in order to increase the conversion ability of glycerol into 1,3-PD by Klebsiella pneumoniae. Using this approach, seven excellent mutants tolerating 1, 3-propanediol with high concentration and producing less byproduct of alcohol are achieved. A high-throughput cultivation method for Klebsiella pneumoniae isolates in 24-well microtiter plates was established. Among 654 mutants, the best producer was identified with a high productivity of 1,3-PD (9.565g/L) in shake flasks, about 32.59% improvement compared with that of the control. In the fed-batch cultures of this mutant, a 1,3-PD titer of 43.525g/L was obtained for 32h, the molar conversion efficiency of glycerol was 53.66%.In this paper we examine the mechanism of inactivation of bacteria by Dielectric Barrier Discharge Plasma in Helium at atmospheric pressure (He DBD). Starch can be effectively hydrolyzed into monosaccharide and disaccharide by He DBD plasma without any additional inorganic acids or enzymes. The concentration of acetic acid and formic acid were 0.2427 g/L and 0.0828 g/L, respectively. The hypothesis is further convinced by the fact that the high acidic bacteria suspension from He DBD led to the hydrolysis of macromolecules in the cell wall and membrane.