Genetically engineered bacterium for producing muconic acid by taking lignin as raw material

The invention discloses a genetically engineered bacterium for producing muconic acid by taking lignin as a raw material. The genetically engineered bacterium is a genetically engineered bacterium obtained by knocking out three genes including a muconate cycloisomerase gene, a catechol 2,3-dioxygenase gene and a protocatechuate 3,4-dioxygenase gene in rhodococcus, and inserting a protocatechuate decarboxylase gene and a protocatechuate codecarboxylase gene. According to the genetically engineered bacterium, a muconic acid degradation pathway in microorganisms is knocked out, so that the straincan utilize the lignin to produce the muconic acid; then a metabolic branch pathway of a muconic acid precursor substance-catechol is knocked out, so that more metabolic flux flows to the muconic acid, and a protocatechuate degradation pathway of the strain is knocked out so as to block the metabolic pathway of protocatechuate; and finally, an exogenous protocatechuate decarboxylase gene and an isoprene cofactor enzyme g