Alkaline Protease Production by an Alkaliphilic Bacterial Isolate Under Solid State Fermentation
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Date
2009-08
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Addis Ababa University
Abstract
A 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).
Description
Keywords
Alkaline protease, isolate C45, solid state fermentation (SSF).