Knockout of pgdS and ggt genes improves ?-PGA yield in B. subtilis

One of the emerging biopolymers that are currently under active investigation is bacterial poly (?-glutamic acid) (?-PGA). However, before its full industrial exploitation, a substantial increase in microbial productivity is required. ?-PGA obtained from the Bacillus subtilis laboratory strain 168 offers the advantage of a producer characterized by a well defined genetic framework and simple manipulation techniques. In this strain, the knockout of genes for the major ?-PGA degrading enzymes, pgdS and ggt, leads to a considerable improvement in polymer yield, which attains levels analogous to the top wild ?-PGA producer strains. This study highlights the convenience of using the laboratory strain of B. subtilis over wild isolates in designing strain improvement strategies aimed at increasing ?-PGA productivity.