Microbial and enzymatic hydrolysis of poly(aspartic acid)

The microbial and enzymatic hydrolysis of poly(aspartic acid) (PAA) has been reviewed. Two PAA-degrading bacteria (Pedobacter sp. KP-2 and Sphingomonas sp. KT-1) were isolated from flesh river water. Pedobacter sp. KP-2 hydrolyzed PAA of high molecular weights over 5000. Sphingomonas sp. KT-1 hydrolyzed only PAA of low molecular weights (<5000), while the cell extract could hydrolyze high-molecular-weights PAA to yield aspartic acid monomer. PAA hydrolase was purified from the cell extract of Sphingomonas sp. KT-1 and characterized. The molecular cloning results indicate that the structure of this enzyme is similar to those of PHB depolymerases and conserves the lipase box as an active center. The results of NMR and GPC analyses showed that this enzyme hydrolyzed the amide bond between aspartic acid units in PAA to yield aspartic acid oligomers.