This invention provides novel strains of microorganisms (e.g., Pseudomonas putida Biotype A) which are capable of converting toluene to muconic acid quantitatively by the ortho(β-ketoadipate) pathway. Muconate lactonising enzyme is not induced in the microorganism, thereby permitting the muconic acid to be produced and accumulated in a quantity greater than one gram of muconic acid per litre of growth medium.