The invention provides a recombinant Escherichia coli host cell for producing an Escherichia coli-asparaginase II enzyme. The host cell includes an Escherichia coli chromosome and at least one copy of a recombinant extrachromosomal vector, wherein the recombinant extrachromosomal vector encodes the L-asparaginase II enzyme, wherein the host cell chromosome also encodes the same L-asparaginase II enzyme, and wherein the host chromosome does not encode any other isoform of L-asparaginase II.