Actinobacillus pleuropneumoniae is a highly infectious and fatal respiratory disease,which has caused seri-ous losses in the pig industry.Apx Ⅱ is one of the main antigens of porcine contagious pleuropneumonia(PCP),which can be used as an effective component of porcine pleuropneumonia vaccine.Corynebacterium glutamicum has the advantages of endotoxin-free and more developed secretion system,and is a very promising recombinant bacterial vaccine protein ex-pression system.The expression system of C.glutamicum was used to produce Apx Ⅱ and achieve its efficient and stable expression,which could provide a research basis for vaccine production.Apx Ⅱ secretory expression strains were constructed in previous studies.In order to further improve the expression yield of Apx Ⅱ,the fermentation in 24-well plates was optimized.The optimal medium was CGXII-YT,and the optimal expression temperature was 30℃.The concentration of IPTG was 1.0 mmol/L,the cul-ture time was 6 h before adding IPTG,and the fermentation culture time was 24 h.The results were the same as those of 24-well plate fermentation.Finally,ApxⅡ was expressed in a 5 L fermentor.Compared with the basic fermentation medi-um,the ApxⅡexpression yield was significantly increased by using CGXⅡ-YT fermentation medium,and the ApxⅡex-pression yield reached 114.60 mg/L under the optimized fermentation conditions.In this study,the secretory expression of Apx Ⅱ in Corynebacterium glutamicum was realized,which provided a basis for its further expansion of production.
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