[Study on the fermentation conditions of recombinant Streptococcus mutans surface protein].

Purpose: To develop the best fermentation process on pET20b(+)-AP/BL21(DE3)plysS expressing recombinant Streptococcus mutans surface protein(rPAc).
Methods: The strains were activated and then cultured in orbital shakers. Pilot test of flask shaking culture was done to get optimized culture conditions, including pH value for culture, type of culture medium, range of culture volume and type of feeding medium. According to the optimal fermentation condition of flask shaking culture, fermentation was carried out with 5L fermentor. The fermentation products were analyzed by SDS-PAGE and Western blot.
Results: The optimum conditions of fermentations were as follows:initial pH 7.2,LB-2 culture medium,the dissolved oxygen concentration maintained at over 30% and feeding medium 10% glycerol+5% yeast extract+5% tryptone.Recombinant protein rPAc could be expressed in the soluble protein formation in flask. The expression of rPAc was about 45% of the total bacterial protein and the final cell density(A600) was 44 in the 5L fermentor. Western blot analysis showed that the fermentation products of rPAc was able to bind anti-PAc antibodies.
Conclusion: The established fermentative procedure provides a basis for further large-scale production of rPAc.