仔猪副伤寒活疫苗合成培养基发酵工艺应用研究

Study on the application on the fermentation process for production of paratyphoid live vaccine in synthetic medium

关键词:  合成培养基  发酵工艺  培养菌数  安全性  免疫原性

Key words:  Synthetic medium  fermentation process  bacteria count  safety  immunogenicity

摘要:

为了确定仔猪副伤寒活疫苗合成培养基发酵参数，本研究根据发酵过程中的关键技术，设计3种不同工艺，分别发酵培养21h，每隔3h取样进行活菌计数表明，培养15～21h均可达细菌稳定期，工艺3培养菌数高于其余2种，其最适培养时间为18h；将合成培养基以1%、2%和3%的接菌量按工艺3分别发酵18h，发现3者培养菌数基本一致。进一步比较4批合成培养基和普通肉汤发酵18h的培养效果，期间15及18h抽样的合成培养基培养菌数分别高普通肉汤12%和25%；发酵18h的菌液对小鼠安全性及对兔的免疫原性，两者基本一致，接种小鼠均10/10健活，免疫攻毒兔均达4/5～5/5保护，对照攻毒兔5/5死亡。因此，发酵培养工艺3可行，可实现仔猪副伤寒活疫苗合成培养基高密度培养，且发酵菌体安全性及免疫原性良好。

Abstract:

Abstract：This study was carried out to identify the fermentation parameters for production of paratyphoid live vaccine in the synthetic medium. According to the key techniques of fermentation, three different fermentation processes were designed to produce Salmonella enterica serovar Choleraesuis (S. Choleraesuis) strain CVCC79500, and the samples were taken out for live bacteria counting every 3 h. The growth of strain CVCC79500 could reach its stationary phase after fermentation for 15-21 h. The obtained bacteria count was higher using the No. 3 process than using the other two, and the optimal fermentation time was 18 h. The strain CVCC79500 was produced in synthetic medium via the No. 3 fermentation process for 18 h with different inoculation amount as 1%, 2% or 3%. The obtained bacteria count was similar with different inoculation amount at 15 h and 18 h. Further, we compared the production for thestrain CVCC79500 for 18 h in either synthetic medium or common broth. The live bacteria count was measured at 15 h and 18 h as well. The average bacteria count was 12% and 25% higher in synthetic medium compared to in common broth at 15 h and 18 h, respectively. Finally, we investigated the safety and immunogenicity of the bacteria harvested at 18 h from both medium. Both culture were safe for immunized mice as the survival ratio (number of alive species / number of vaccinated species) of 100% (10/10). Also both culture showed the protective ratio (number of protected species / number of challenged species) of 80-100% (4/5-5/5), with the mortality (number of died specied / number of challenged species) for non-vaccinated control of 5/5. Therefore, the No.3 fermentation process was workable and can achieve the high density cultivation of paratyphoid live vaccine in synthetic medium. The fermented bacteria were safe and had good immunogenicity. Keywords: Synthetic medium；fermentation process；bacteria count； safety； immunogenicity