CHARACTERIZATION OF ALKALINE-AMYLASE PRODUCING BACILLI SP. FROM A KENYAN SODA LAKE OTIENO SARAH ATIENO REG.NO. H12/ 3170/ 2009 ABSTRACT Alkaline amylases have high catalytic efficiency and stability at the alkaline pH ranging from 9 to 11, and have potential applications for hydrolyzing starch under high pH conditions in the starch and textile industries and as ingredients in detergents for automatic dishwashers and laundries. While alkaline amylases have potential applications in the textile and detergent industries, relatively few efforts have been made to explore the microbial diversity of soda lakes for their novel amylases which are associated with high optima activities and stability properties at high pH. In this study, a total of seven pure microbial soda lake isolates, previously obtained from Lake Bogoria water, were used as source of alkaline amylases. The isolates were initially screened for amylase-producers and those found to be positive for the same were characterized and cultivated via submerged fermentation for amylase production. During the screening, six isolates (designated LBW 2.1 2; LBW 2.1 4; LBW 2.2 7; LBW4.3 3, LBW 4.4 7 and LBW 4.4 8) exhibited extracellular starch hydrolyzing activity and were selected by presence of clear zones or ‘halos’ around the colonies after staining with Gram’s iodine solution. Morphologically, the cells were rod-shaped, motile, formed terminal spores, and were catalase- and Gram-positive. Their colonies were circular in shape, cream in colour, mucoid in texture, opaque in terms of optical density, and had smooth surfaces with raised elevations. The screening conditions resulted in growth of microorganisms typically related to alkaliphilic Bacilli. Culturally, the microorganisms were aerobic alkaliphiles with optimum pH and temperature of growth at 10.5 and 550C, respectively. The microorganisms could also tolerate salinity up to 10% (w/v) NaCl, as well as utilize different sugars for growth. The growth properties of these isolates appear to be similar to those of B. halodurans sp., implying that they could belong to this species. When the isolates were cultured using starch as sole carbon source via submerged fermentations at pH 10.5, growth was observed. Cell-free culture supernatants from all isolates were seen to possess varying levels of starch hydrolyzing activities over the 72 h period the isolates were cultured. Although maximum amylase activity was 0.1058 IU/mL/min by isolate LBW2.1 4, it is interesting to note that isolate LBW2.2 7 secreted the most stable enzyme over the entire cultivation period. This makes it a suitable potential candidate for application in industrial processes requiring high pH e.g. de-sizing of textile and detergent formulation.