Gessesse, Amare(PhD)Haile, Gizachew2018-07-022023-11-182018-07-022023-11-182009-08http://etd.aau.edu.et/handle/12345678/5253A total of 240 alkaliphilic microorganisms isolated from samples collected from alkaline soda lakes of Ethiopia were screened for the production of alkaline proteases. Of these, 30% were protease positive indicating the abundance of protease producing microorganisms in these habitats. This again is a reflection of the abundance of protein substrates in the form of bird`s feather and left over from dead cells of spirulina and other microorganisms. Out of the 80 protease positive isolates, 20 (25%) grew well and produce appreciable level of enzyme activity when grown in solid state culture. Of these, one isolate designated as C45 was selected for further study. The protease produced by isolate C45 was characterized to determine its potential industrial application. The enzyme was active in the pH range of 6.5-11.5, with optimum activity at pH 8-9; and stable at alkaline pH. The optimum temperature for activity was 40°C and 50°C in absence and presence of 5mM of Ca+2, respectively. The enzyme displayed appreciable activity and stability at low temperature. These properties suggest that protease C45 could find potential application for dehairing and detergent at moderate temperature. When protease C45 was added to raw hide enabled dehairing, suggesting the potential usefulness of the enzyme in the leather industry. The commercial application of enzymes greatly depends on the cost of the enzyme which again is determined by the production cost of the enzyme. Currently most commercially available enzymes are produced through capital intensive submerged fermentation (SmF). An alternative method for the growth of microorgianims which is currently receiving significant attention is solid state fermentation (SSF). In this study, isolate C45 was grown under solid state fermentation using wheat bran as the growth substrate. Maximum protease secretion was achieved at inoculum size of 20% (v/w), bran to moistening agent ratio of 1:2 when incubated at 30°C for 144 hr. Addition of inorganic nitrogen sources and organic carbon sources as a supplement of SSF medium repressed protease induction. These results indicate that the microbial isolate shows a good potential for production of low cost alkaline protease by using inexpensive substrate such as wheat bran alone and/or low cost complex nitrogen source such as Millettia ferruginea (Berbra) seed flour as supplement in SSF. Key words: Alkaline protease, isolate C45, solid state fermentation (SSF).enAlkaline proteaseisolate C45solid state fermentation (SSF).Thesis