[The diploid of genetically engineered yeast for expression of hybrid HBsAg gene SA-28].

By mating a yeast haploid expressing hybrid HBsAg gene SA-28, Y19/YFD158, with another hapolid Y95, the diploid Y95xY19/YFD158 was constructed. The experiments showed that the cell density of the diploid in fermentation was three time higher than that of the haploid, the stability of expression vector in the diploid was much higher than in the haploid, the xpression level of hybrid HBsAg gene of the diploid was more than three time higher than that of the haploid and the average cope number in diploid cell was a little lower than that in the haploid.