A method of obtaining 7-aminodesacetoxycephalosporanic acid (7-ADCA). The method is based on the use of desacetoxycephalosporin C (DAOC) produced directly by fermentation of Acremonium chrysogenum (also called Cephalosporium acremonium) and catalysed by the enzymatic activities D-amino-acid oxidase (DAO) and glutaryl-7-ACA acylase (GLA). The method of production of DAOC by fermentation of A. chrysogenum is based on inactivation of the cefEF gene and subsequent expression of the cefE gene giving rise to the strain A. chrysogenum △cefEF-cefE. The invention includes the following sections: (I) inactivation of the cefEF gene of A. chrysogenum, which codes for the enzymatic activities desacetoxycephalosporin C synthase (DAOCS or expandase) and desacetylcephalosporin C synthase (DACS or hydroxylase), (II) expression of the cefE gene, which codes for the enzymatic activity DAOCS, derived from an actinomycete in the transformant of A. chrysogenum inactivated in the cefEF gene, (III) development of a method of fermentation of the recombinant strain for the production of DAOC and (IV) enzymatic conversion of DAOC to 7-ADCA catalysed by the enzymes DAO and GLA. Alternatively, it would be possible to produce 7-ADCA directly by fermentation of A. chrysogenum by combined expression of the genes that code for DAO and GLA in the DAOC-producing strain A. chrysogenum △cefEF-cefE or by expression of a gene that codes for the enzyme cephalosporin acylase in A. chrysogenum △cefEF-cefE.