Abstract: Lysozyme is a natural antibacterial agent,which could directly hydrolyze the bacterial cell wall to generate antibacterial activity,however,the property that lysozyme only has antibacterial activity against Gram-positive bacteria limits its application in the field of food and breeding.Lysozyme is a protein with small molecule,more and more studies have modified lysozyme to improve its antibacterial activity and expand its antibacterial spectrum.This paper mainly reviewed that the antibacterial activity of lysozyme had been greatly improved after modification using high temperature,pH,metal ions,chemical modification,combination with nanomaterials or other solutions,and genetic engineering technology,especially for Gram-negative bacteria.The bacteriostatic activity of lysozyme can be improved by the following ways:①Destroying the non-covalent binding within the enzyme molecule by raising the temperature;②Affecting the molecular space structure of the enzyme by reducing pH;③Adding metal ions;④Chemical modification of side chain group or chemical group of enzyme molecule;⑤Lysozyme is loaded on nano materials and fixed into nanocomposites to destroy cell walls;⑥The lysozyme and other solutions inhibiting the growth of bacteria are mixed to obtain a composite solution;⑦Construction of new lysozyme expression vector using gene recombination technology.The research and transformation of lysozyme has important guiding significance for the development of basic science,the application of lysozyme in aquaculture and livestock breeding instead of antibiotics,and the development of green natural food preservatives.

Key words: lysozyme; hen egg-white lysozyme; antibacterial activity; protein modification