Improved production of poly(γ‐glutamic acid) by Bacillus subtilisRKY3 and its recovery from viscous fermentation broth as a biodegradable polymer

Abstract

BACKGROUND Physiological parameters (culture pH, aeration rate, and agitation speed) were optimized to improve γ‐PGA production by batch culture of Bacillus subtilis RKY3. The optimum conditions for recovery of γ‐PGA from highly viscous culture broth were also investigated. RESULTS Enhanced γ‐PGA production (41.4 g L−1, 397 cP) was observed under optimized physiological culture parameters (no pH control, 1.5 L min−1 aeration, and 300 rpm agitation). The cells were completely removed by diluting the viscous culture broth 7.5‐, 5.0‐, and 2.5‐fold at pH 6.0, 4.0, and 2.0, respectively. Maximum recovery of γ‐PGA was observed when the volume ratio of cell‐free culture broth to cold ethanol was 1:5 at pH 6.0. γ‐PGA with a molecular weight <100 kDa was successfully excluded in an ultrafiltration system to develop more economical recovery of γ‐PGA from cell‐free culture broth, which resulted in efficient γ‐PGA concentration with a molecular weight >100 kDa. CONCLUSION The physiological parameters affecting γ‐PGA production were optimized, and the isolation and recovery of γ‐PGA from viscous culture broth was also evaluated. Cells were removed completely by diluting the culture broth, and precipitation of γ‐PGA using cold ethanol was better than that of other alcohols. Ultrafiltration was found to be an efficient recovery method for concentration of culture broth containing γ‐PGA. © 2013 Society of Chemical Industry

Poly-(γ-glutamic acid) Production and Optimization from Agro-Industrial Bioresources as Renewable Substrates by Bacillus sp. FBL-2 through Response Surface Methodology

“…Yoon et al [23] achieved only 35 g/L of γ-PGA with 1g/L/h productivity using optimized fed-batch fermentation by Bacillus licheniformis. Jeong et al [24] and Zhang et al [9] also reported similar low production of γ-PGA using Bacillus subtilis RKY3 and an optimized fermentation process. Table 3.…”

Proteomic profiling of Bacillus licheniformis reveals a stress response mechanism in the synthesis of extracellular polymeric flocculants

“…licheniformis CGMCC2876 contains an abundant amount of amino sugars (Xiong et al, ), and polysaccharides can also be used as carbon or nitrogen sources(Ferreira et al, ; Zhurina et al, ). Similarly, there are studies reporting that microorganisms secrete γ‐PGA depolymerase to degrade γ‐PGA as a nutrient source when the medium only contains γ ‐PGA (Jeong et al, ; Kunioka and Goto, ). Our research provides culture strategies for improving the production of biopolymeric flocculants by B .…”

Improvement of Bacillus subtilis for poly‐γ‐glutamic acid production by genome shuffling

“…The majority studies on γ‐PGA strains have been focused on wild‐type Bacillus species, such as B. subtilis IFO3335 (Goto and Kunioka, ), B. subtilis F‐2‐01 (Kubota et al ., ), B. subtilis NX‐2 (Xu et al ., ), B. subtilis ZJU‐7 (Shi et al ., ), B. subtilis RKY3 (Jeong et al ., ), B. licheniformis ATCC 9945a (Ko and Gross, ), B. licheniformis WX‐02 (Wei et al ., ) and B. amyloliquefaciens LL3 (Cao et al ., ), which produced γ‐PGA usually at the yields of more than 10 g l −1 . However, the yield of γ‐PGA still need to be further improved.…”