Alkaline Protease Production By An Alkaliphilic Bacterial Isolate Under Solid State Fermentation

A total of 240 alkaliphilic microorganisms isolated from samples collected from alkaline soda lakes ofrnEthiopia were screened for the production of alkaline proteases. Of these, 30% were protease positivernindicating the abundance of protease producing microorganisms in these habitats. This again is arnreflection of the abundance of protein substrates in the form of bird`s feather and left over from deadrncells of spirulina and other microorganisms. Out of the 80 protease positive isolates, 20 (25%) grewrnwell and produce appreciable level of enzyme activity when grown in solid state culture. Of these, onernisolate designated as C45 was selected for further study. The protease produced by isolate C45 wasrncharacterized to determine its potential industrial application. The enzyme was active in the pH range ofrn6.5-11.5, with optimum activity at pH 8-9; and stable at alkaline pH. The optimum temperature forrnactivity was 40°C and 50°C in absence and presence of 5mM of Ca+2, respectively. The enzymerndisplayed appreciable activity and stability at low temperature. These properties suggest that proteasernC45 could find potential application for dehairing and detergent at moderate temperature. Whenrnprotease C45 was added to raw hide enabled dehairing, suggesting the potential usefulness of thernenzyme in the leather industry. The commercial application of enzymes greatly depends on the cost ofrnthe enzyme which again is determined by the production cost of the enzyme. Currently mostrncommercially available enzymes are produced through capital intensive submerged fermentation (SmF).rnAn alternative method for the growth of microorgianims which is currently receiving significantrnattention is solid state fermentation (SSF). In this study, isolate C45 was grown under solid staternfermentation using wheat bran as the growth substrate. Maximum protease secretion was achieved atrninoculum size of 20% (v/w), bran to moistening agent ratio of 1:2 when incubated at 30°C for 144 hr.rnAddition of inorganic nitrogen sources and organic carbon sources as a supplement of SSF mediumrnrepressed protease induction. These results indicate that the microbial isolate shows a good potential forrnproduction of low cost alkaline protease by using inexpensive substrate such as wheat bran alone and/orrnlow cost complex nitrogen source such as Millettia ferruginea (Berbra) seed flour as supplement inrnSSF.rnKey words: Alkaline protease, isolate C45, solid state fermentation (SSF).

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