High yield and cost‐effective production of poly(γ‐glutamic acid) with Bacillus subtilis

Abstract

AbstractPoly(γ‐glutamic acid) (γ‐PGA) is a promising biopolymer with many potential industrial and pharmaceutical applications. To reduce the production costs, the effects of yeast extract and L‐glutamate in the substrate for γ‐PGA production were investigated systematically at shake flask scale. The results showed that lower concentrations of yeast extract (40 g/L) and L‐glutamate (30 g/L) were beneficial for the cost‐effective production of γ‐PGA in the formulated medium. By maintaining the glucose concentration in the range of 3–10 g/L via a fed‐batch strategy in a 10‐L fermentor, the production of γ‐PGA was greatly improved with the highest γ‐PGA concentration of 101.1 g/L, a productivity of 2.19 g/L·h and a yield of 0.57 g/g total substrate, which is about 1.4‐ to 3.2‐fold higher than those in the batch fermentation. Finally, this high‐density fermentation process was successfully scaled up in a 100‐L fermentor. The present work provides a powerful approach to produce this biopolymer as a bulk chemical in large scale.