Production of amylases from Bacillus amyloliquefaciens under submerged fermentation using some agro-industrial by-products

Abstract

Thirty-one bacterial isolates out of 133 isolates, were obtained from rhizosphere of Egyptian clover plants, and had variant capability for starch degradation on starch agar medium. The isolate E109 was the most potent being 72.5 U ml 1 and 2.5 for amylase activity and starch hydrolysis ratio (SHR), respectively, at 50 C. The potent isolate E109 was identified based on phenotypic characteristics, phylogenetic positions based on 16S rRNA gene analysis and base sequences (submitted to NCBI Gen Bank). 16S rRNA gene analysis confirmed that this isolate belonged to the genus Bacillus and it was most closely related to B. amyloliquefaciens (95% similarity). For the production of amylases, nine agro-industrial residues were added as carbon sources to the basal medium. The medium supplemented with potato starchy waste as the sole carbon source enhanced the enzyme activity more than soluble starch as control for a, b and c amylases activity, as it increased by B. amyloliquefaciens about 1.26 & 4 and 8-fold, respectively after 48 h at 50 C using rotary shaker at 150 rpm. B. amyloliquefaciens gave the maximum values of a, b and c amylases activity on medium supplemented with 2% potato starchy waste after 30, 30 & 36 h of fermentation periods at 50 C using shake flasks technique as a batch culture. These values were 155.2 U ml 1 (R2 =0.93), 1.0 U ml 1 (R2= 0.94) and 2.4 U ml 1 (R2 =0.95), respectively. It could be stated that productive medium supplemented with 2% potato starchy waste as a low price substrate could be more favorable than basal medium containing 1% starch for amylases production in submerged fermentation, as it increased a, b and c amylase activity by 1.98, 7.69 and 12-fold than that produced in basal medium (control), respectively.