Optimization of Some Nutritional Conditions and α- Ketoglutaric Acid Concentration as PGA Precursor for Maximizing PGA Production from Bacillus sp. 42 and Bacillus sonorensis 44
Rania F. Ahmed *
Department of Agricultural Microbiology, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Cairo 11241, Egypt.
*Author to whom correspondence should be addressed.
Abstract
Poly gamma glutamic acid is a biodegradable, water soluble and non-toxic edible biopolymer, PGA has nylon back bone similar structure and expressed as bio-nylon. Various bacterial strains produced PGA on of them Bacillus sp. such as B. subtilis, B. lichanformans and B. sonorensis. Polymer yield was affected with medium composition as nitrogen and carbon sources. The current experimental was carried out using shake flask technique for PGA production during 72 of fermentation. The highest biomass was achieved at glycerol media and glucose media for PGA yield and productivity being 2.31, 9.65 gl-1 and 0.134 gl-1h-1, respectively of B. sonorensis 44. Of nitrogen source, organic source (yeast extract) was higher PGA yield and productivity than inorganic sources (NH4NO3) which reduced PGA yield about 28.7 and 36.02% of Bacillus sp. 42 and B. sonorensis 44, respectively. Production media supple- mented with 0.5 and 0.75 gl-1 α-keto-glutaric acid increased PGA yield about 1.24fold for both Bacillus strains. Osmotic pressure of 2.55 MPa (3% NaCl) enhanced PGA yield about 1.18 and 1.24fold of Bacillus sp. 42 and B. sonorensis 44, respectively. Furthermore, the highest PGA was received using medium containing glucose and yeast extract (as C and N2 sources). α-keto-glutaric acid and osmotic potential has an induction effect for polymer accumulation.
Keywords: γ-PGA, carbon sources, nitrogen sources, α-Keto-glutaric acid, NaCl osmotic stress, Bacillus sp.42 and B. sonorensis 44