Provided herein are penicillin expandase mutants, DNA coding the mutants, reagent kit containing the mutants and the application. The penicillin expandase mutants using SEQ ID NO.: 2 in the Sequence Listing as a reference sequence, have at least one amino acid mutation at residue positions corresponding to threonine at position 42 and glutamine at position 126, wherein, amino acid at position 42 is substituted by any other natural amino acid except threonine, amino acid at position 126 is substituted by any other natural amino acid except glutamine. The penicillin expandase mutants of present invention have increased its thermostability and catalytic activity; it is more suitable for commercial and industrial applications.

Provided herein are compositions and methods for stabilizing enzymes. Also provided are systems, compositions and methods for using the stabilized enzymes to produce a desired compound.

Disclosed herein are a microorganism with excellent deacetoxycephalosporin C (DAOC) productivity and a use thereof. A mutant microorganism with improved DAOC productivity and a use thereof for producing 7-aminodeacetoxycephalosporanic acid (7-ADCA) are provided.

Provided herein are penicillin expandase mutants, DNA coding the mutants, reagent kit containing the mutants and the application. The penicillin expandase mutants using SEQ ID NO.: 2 in the Sequence Listing as a reference sequence, have at least one amino acid mutation at residue positions corresponding to threonine at position 42 and glutamine at position 126, wherein, amino acid at position 42 is substituted by any other natural amino acid except threonine, amino acid at position 126 is substituted by any other natural amino acid except glutamine. The penicillin expandase mutants of present invention have increased its thermostability and catalytic activity; it is more suitable for commercial and industrial applications.