BIOPRODUCTION OF γ-POLY(GLUTAMIC ACID) USING FEATHER HYDROLYSATE AS A FERMENTATION SUBSTRATE

Abstract

Polyglutamic acid (PGA) is water-soluble and biodegradable polymer with high production cost. For feasible PGA production, feather hydrolysate (FH) was used as fermentation substrate. 30L fermentation of native feather was realized to obtain keratinase enzyme using Streptomyces pactum DSM 40530. Fermentation broth was concentrated by cross-flow filtration where the enzyme activity increased by 8.75-fold and 8x10(3)UL(-1)d(-1) of enzyme activity was the optimum for achieving 75% degradation per gram of feather. 40g/L of FH was used with different media compositions to produce PGA using Bacillus licheniformis 9945a. Among four different cultivation where L-glutamate, tri-sodium citrate and glycerol were used as the constituents of Medium E, highest yields of gamma-PGA and cell dry matter (CDM) were obtained from cultivation-1, at 5.4 +/- 0.4 and 8.6 +/- 0.5g/L, respectively, despite the culture media did not contain glutamic acid. In cultivation-2, which was not only missing glutamate but also citrate, the gamma-PGA and CDM yielded 3.2 +/- 0.2 and 7.8 +/- 0.4g/L, respectively whereas it was only 1.9 +/- 0.2 and 4.2+0.4g/L when FH was used as the sole substrate in cultivation-3. When cultivation-4 was adopted where only glycerol was missing, the gamma-PGA and CDM yields slightly increased to 2.3 +/- 0.2 and 5.5 +/- 0.3g/L, respectively. This is the first study that achieved the production of gamma-PGA from FH.