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

Poly-Trimethylene Terephthalate (PPT) has numerous promising properties andapplications. As a pivotal monomer for the synthesis of PTT, 1,3-propanediol(1,3-PD) has attracted particular attention of many famous corporations in the worldin these years. Compared with chemical synthesis,microbial fermentations of 1,3-PDhave many obvious advantages,including the environmental friendship and priceadvantage and thus become the focuses of research.The inhibition of products onmicroorganism cells will limit the product titer and the yield of 1,3-PD onglycerol,and thus lead the product recovery and purification to a troublesome task.These problems may be effectively solved if some mutants with tolerance to highconcentration of 1,3-PD and less byproducts were obtained by selective breeding.In this study an induced mutation technology of liquid phase and solid phase byplasma combining three times concentrating is established in order to increase theconversion ability of glycerol into 1,3-PD by Klebsiella pneumoniae. Using thisapproach, 2 excellent mutant strains tolerating 1,3-propanediol with a highconcentration and producing less alcohol are obtained. As a result, 1,3-PDconcentration of K.908 yield was 19.30g/L with the anerobic batch fermentation andincreased by 22.81% than the control strain, K1207 strain production was70.5226g/L by microaerobic fed-batch fermentation. A high-throughput cultivationmethod for Klebsiella pneumoniae isolates in 24-well microtiter plates wasestablished. Among 654 mutants, the best producer was identified with a highproductivity of 1,3-PD(9.57g/L) in shake flasks, about 32.59% increase comparedwith the control. In the fed-batch cultures of this mutant, a 1,3-PD concentration of43.53g/L was obtained for 32 hours, the molar conversion efficiency of glycerol was53.66%. All these three strains have genetic stability. As we use the cold plasma atatmospheric pressure, it is more simple, safe, and highly effective than other plasma.In this paper we examine the mechanism of inactivation of bacteria by DielectricBarrier Discharge Plasma in Helium at atmospheric pressure (He DBD). He DBDcan led to the high acidic bacteria suspension, the macromolecules in the cell walland membrane could be hydrolyzed, such as protein can be hydrolyzed into aminoacid by He DBD plasma.