Process Biochemistry, Vol.57, 9-15, 2017
Microbial levan from Brachybacterium phenoliresistens: Characterization and enhancement of production
Levan producing bacteria was isolated from rhizosphere soil. The molecular identification"of this isolate was conducted using 16S rRNA, which resulted in a sequenced region of 1298 base pairs. The sequence alignment in the gene bank indicated that this isolate has a high percentage of similarity (99%) to the retrieved consensus sequence of Brachybacterium phenoliresistens strain phenol-A. The produced levan was characterized using TLC, FTIR, 1H NMR and 13C NMR spectroscopy techniques. The effects of nutritional and physical factors on this isolate's levan production were investigated. The results demonstrated that the optimal sources for carbon and casein during levan production were sucrose and casein, yielding 7.88 g/l and 8.12 g/l of levan, respectively. The highest levan yield (7.97 g/l) was obtained at a sucrose concentration of 300 g/l. At an initial pH of 7.8, this bacterium yielded their highest levan production of 7.88 g/l. The optimal incubation period was 72 h with a yield of 8.58 g/l, the optimal temperature was 30 degrees C and resulted in 7.87 g/l, and the highest levan production yield was obtained at 150 rpm and yielded 8.12 g/l. (C) 2017 Elsevier Ltd. All rights reserved.
Keywords:Levan;Brachybacterium phenoliresistens;Rhizosphere soil;Nutritional factors;Physical factors