治疗性双质粒HBV DNA疫苗工程菌的中试发酵工艺研究

Pilot Fermentation Procedure of Recombinant E. coli Strain Containing Two Plasmids as Therapeutic HBV DNA Vaccine

目的研究双质粒HBV DNA疫苗工程菌的中试发酵工艺。方法首先通过计算质粒拷贝数，检测工程菌DH5α/pS2．S和DH5α/pFP在传代过程中的遗传稳定性，通过摇瓶培养确定培养基组成，再在30L发酵罐内，通过改变培养基成分、培养时间、补料方式，确定最佳发酵参数。并将确定的最佳发酵参数应用于50L发酵罐连续3批中试规模的发酵，同时考察在发酵培养过程中质粒稳定性和超螺旋质粒DNA的比例。结果工程菌DH5α/pS2．S和DH5α/pFP在连续传代30次后，质粒拷贝数保持稳定。确定最佳发酵参数为以甘油为碳源的培养基培养，梯度恒速流加方式补料，培养时间为10h。通过3批稳定发酵，最终可获得湿菌58．0～71．8g／L，质粒含量可达到1．11～1．58mg／g菌，超螺旋质粒DNA的比例达93％以上。结论已建立了稳定的双质粒HBV DNA疫苗工程菌中试发酵工艺，为进一步规模化生产奠定了基础。

Objective To explore the pilot fermentation procedure of recombinant E. coli strain containing two plasmids as therapeutic HBV DNA vaccine. Methods Transform the recombinant plasmids pcDNAS2. S（pS2. S） and pcDNAIIF（pFP） constructed by the authors to E. coli DHSot to obtain recombinant E. co/i strains DH5α/pS2. S and DH5α/pFP respectively. Test the genetic stabilitias of the two strains during subculture by calculating the copy number of plasmids. Determine the composition of medium by shakeflask culture. Optimize the fermentation parameters of the two strains in 30 L fermentor by altering medium, culture time and the mode of fed-batch. Ferment 3 consecutive batches of recombinant strains in 50 L fermentor by the optimal fermentation procedure. Meanwhile, explore the plasmid losing rate and the proportion of supertwisted plasmid DNA during fermentation. Results The copy number of plasraids of recombinant strains DH5α/pS2. S and DH5α/pFP were stable during subculture for 30 passages. The optimal medium for fermentation was that using glycerol as a carbon source;the optimal culture time was 10 h;the optimal mode of fed-batch was gradient feeding at a constant rate. By using the procedure, the wet weight, plasmid content and proportion of supertwisted plasmid DNA of fermentation product reached 58.0-71.8 g/L, 1.11-1.58 mg/g bacteria and more than 93% respectively. Conclusion A stable pilot fermentation procedure of recombinant strains DH5α/pS2. S and DH5α/pFP was developed. It laid a foundation of large-scale production of therapeutic HBV DNA vaccine.