Research On The Fermentation Process Optimization And Pilot Production Of A Mutation L-threonine Production Strain 1905#

At present,L-Threonine produced by fermentation is being wide-spread used in this latest ten years development,China has become the largest country of threonine production all over the world,however,the capacity expansion speed of global threonine is even faster than the growth rate of market demand,which shows a serious overcapacity status,in the global threonine production,market competition is fierce.In order to improve enterprise competitive capability,we focused our researches on the optimization of fermentation process with the Genetic engineering bacteria Escherichia coli THR6 1905# strain provided by Star Lake bioscience co.,Inc.Zhaoqing Guangdong,the relative research contents and results are as follows:1.As compared with original strain,The fermentation level of the 1905# strain was validated in 50 L fermentor tank relative parameters for 1905# strain have been basically figured out.The studies showed that the acid yield of 1905# reached 130 g/L,the conversion rate reached 53%,as compared with the original strains whose acid yield 110 g/L and sugar acid conversion rate 50%,the acid yield and the conversion rate was increased by about 18.2% and 6% respectively.On the other hand,the Optical density(OD)of the fermentation broth with 1905# strain was also improved,under the condition that the dissolved oxygen was met the value greater than 20%,the stirring speed and ventilation rate was lower than the original strain,which is much more energy conservation.2.Brown sugar was added in the initial fermentation culture as part of carbon source and the growth promoting agent,and nitrogen source we used ammonium sulfate and yeast extract,through the contrast test,the cheaper molasses was used instead of red sugar,corn syrup was used instead of yeast extract,the amount of molasses and corn syrup were 2 g/L and 8 g/L respectively.And optimize the amount of ammonium sulphate to 0.5 g/L,under the above condition,the acid yield of threonine in 50 L fermentation tank scale fermentation raised to 140 g/L,and the sugar acid conversion rate increased to 55%.3.According to the fermentation optimization result in 50 L fermentor tank,we furthermake trials in pilot plant with 1905# strain in a 12 m3 fermentor tank,according to the results of the fermentation process and combined with pilot equipment to determine material protocol,that is 0.15% of sugarcane molasses,8 g/L of corn steep liquor,0.15 g/L of ammonium sulfate,with this formula,the acid yield was 135 g/L,the sugar acid conversion rate was 57%.The researches on threonine fermentation in China are mainly in shake flask and small fermentation tank scale,there are few reports of more than 10 t fermentation tank,and most of the fermentation level is low,which doesn’t comply with the situation of domestic threonine fermentation level,this paper has certain research value in improving the fermentation level of threonine commercial process,at the same time,it provides a certain help to understand the domestic threonine industry development.