The propagation modes of yeast can be divided into sexual reproduction and asexual reproduction, with asexual reproduction as the main one. Bud propagation is the most common asexual propagation method of yeast. Some yeasts reproduce by cell division, which is called division. The sexual reproduction of yeast generally produces ascospores, and its formation process is that two cells of different sexes approach each other, each cell protrudes a small protuberance to connect, the cell wall at the junction dissolves, and the cytoplasm of the two cells fuses, which is called plasmolysis.

Then the fusion of two haploid nuclei is called nuclear matching, forming a diploid nucleus, and the original cell forms a zygote. The combined nuclei undergo meiosis to form 4 or 8 nuclei, and the protoplasm centered on the nucleus is concentrated and expanded to form spores. The initial zygote is called ascospores, and the spores in it are called ascospores. Many diploid cells of yeast can be used for vegetative growth and generation reproduction. Therefore, there are two types of haploid cells and diploid cells in the life cycle of yeast, which can live independently. Diploid yeast has large cells and strong vitality, so the fermentation industry often uses diploid yeast for production.