Bioproduction of poly-γ-glutamic acid with diverse molecular weights in Bacillus subtilis

Abstract:

[Background] Poly-γ-glutamic acids (γ-PGAs) with different molecular weights are of high application value in agriculture, cosmetics, and medicine, and biosynthesis of γ-PGA with specific molecular weights has attracted the interest of scholars. [Objective] To synthesize γ-PGAs of different molecular weights in a γ-PGA producer, Bacillus subtilis KH2. [Methods] Three γ-PGA hydrolases of B.subtilis PgdS, B.subtilis YwtE, and B.licheniformis SGH, were heterologously expressed and their hydrolytic capacities were investigated. γ-PGAs with different molecular weights were yielded in B.subtilis KH2 through the modification of enzymatic degradation conditions. [Results] All the three hydrolases can cleave high-molecular-weight γ-PGA into low-molecular-weight γ-PGA, particularly PgdS. The molecular weight of γ-PGA decreased from 1 600 kDa to 180 kDa with the addition of PgdS. Finally, the addition amount and time of PgdS were optimized to yield γ-PGA with the molecular weight of 210-600 kDa in KH2. [Conclusion] γ-PGAs with diverse molecular weights were synthesized in B.subtilis KH2 through the controllable treatment with hydrolase. This study provided a promising approach for the sustainable production of γ-PGA with different molecular weights in a wide range under mild synthesis conditions.

Key words:γ-PGA;molecular weight;hydrolase;Bacillus subtilis