发酵后期补加2种氮源对克雷伯氏菌合成1，3-丙二醇的影响

Influences on the biosynthesis of 1,3-propanediol in Klebsiella pneumonia by feeding two types of nitrogen source at the late stage of fermentation

为探寻解决重要平台化合物1,3-丙二醇发酵后期菌体生长和1,3-丙二醇合成受限的方法,通过从菌体量、产物和关键酶活性及基因转录水平等方面,较全面地考察了发酵后期补加酵母膏和硫酸铵对克雷伯氏菌(Klebsiella pneumoniae)合成1,3-丙二醇的影响,结果为:添加两种氮源均有利于菌体生长;补加10 g/L酵母膏和硫酸铵,1,3-丙二醇产量由58.6 g/L分别提高到70.6 g/L和77.2 g/L;相对于酵母膏,硫酸铵对关键酶活性的增强更为明显,并使甘油脱氢酶(glycerol dehydrogenase,Dha D)在发酵后期始终维持较高水平,促进细胞生长和产物合成。此外,与补加酵母膏相比,补加硫酸铵后关键酶基因转录水平上调并不显著。表明硫酸铵主要通过直接激活关键酶活性促进细胞生长和产物合成。综上所述,发酵后期补加硫酸铵更利于1,3-丙二醇的生物合成,是提高发酵合成1,3-丙二醇水平的有效方式之一。

1,3-Propanediol （1,3-PDO） is an important platform compound. In order to solve the restriction of cell growth and 1,3-PDO production at the late stage of fermentation, feeding of two types of nitrogen source （yeast extract and ammonium sulphate） at the late stage of fermentation was studied. Biomass, products, genes transcription level and activities of key enzymes were studied. The results showed that both yeast extract and ammonium sulphate feeding improved the cell growth, and the 1,3-PDO titers were increased from 58.6 g/L to 70.6 g/L and 77.2 g/L, respectively. In comparison with yeast extract, the feeding of ammonium sulphate further improved activities of key enzymes involved in 1,3-PDO synthesis, and maintained glycerol dehydrogenase （DhaD） at a higher level at the late stage of fermentation. However, the transcription levels of the key genes of the cells incubated with the feeding of different nitrogen source were similar. All above information proved that ammonium sulphate improved the cell growth and product yield by activation of enzymes activities but did not affect their genes transcription. These results suggested that the addition of ammonium sulphate at the late stage of fermentation would be an effective way to improve the biosynthesis of 1,3-PDO.