This paper was completed under the careful guidance and strong support of teacher XX. Teacher X's rigorous and realistic learning attitude, high professionalism, serious and diligent work style and enterprising spirit of bold innovation have had an important impact on me.

Her profound knowledge, broad vision and keen thinking deeply touched me. At the same time, during the graduation project, I also learned a lot about microbial fermentation, and my experimental skills have been greatly improved.

In addition, I would like to thank my senior sister for her guidance in my experiment and thesis writing. She helped me finish this paper. I would also like to thank XX and XX for their selfless help, which enabled me to finish my thesis smoothly. At the same time, Mr. XX often helps me in the laboratory, and I also sincerely thank him here.

Finally, thank you again for your concern and help.