Fermentation improvement of L-lysine by response surface analysis and additional nitrogen source

To increase L- lysine concentration and conversion ratio, methionine, molasses and glutamate proved to be the most significant factors in the fermentative medium by Placket- Burman experiments.In response surface methodology design experiments, these three factors ' optimum concentrations were respectively 0.195g /L, 15.70mL /L and 0.215g /L, when L- lysine production was improved from 1.90g /100mL to 2.25g /100mL.When additional 10g /L ( NH4) 2SO4was added into the fermentative medium, L-lysine production was further increased to 2.41g /100mL, and fermentation period was decreased from 30 hours to 25 hours.By optimizing medium and improving nitrogen source, production cost of L-lysine was greatly decreased.