What is claimed is:
1. A mutant strain, named Lactococcus lactis WH101, with higher acid tolerance than that of its parent strain, which was deposited on Apr. 29, 2016 in the Chinese Type Culture Collection with the accession CCTCC NO: M 2016233, which is located Wuhan University, Wuhan, China.
CROSS-REFERENCES AND RELATED APPLICATIONS
This application claims the benefit of priority to Chinese Application No. 201610652096.9, entitled “A mutant strain of Lactococcus lactis and its application”, filed Aug. 10, 2016 and is a continuation application of international application No. PCT/CN2016/108476, filed Dec. 5, 2016, which are herein incorporated by reference in their entirety.