Evaluation of the Effects of Nutritional and Environmental Parameters on Extracellular Protease Production by Stenotrophomonas acidaminiphila Strain BPE4

Author(s): Philomena Edet, Atim David Asitok, Maurice George Ekpenyong, Sylvester Peter Antai

An aerobic mesophilic Gram-negative rod-shaped bacterium isolated from fermenting bean processing effluent (BPE) and identified as Stenotrophomonas acidaminiphila strain BPE4, produced an extracellular protease on skimmed-milk minimal medium. Time-course of enzyme production revealed peak productivity at 12 h but enzyme concentration gradually increased till 36 h beyond which both concentration and productivity gradually decreased. Evaluation of the influences of major nutritional sources on enzyme concentration revealed significant (P < 0.05) effects of fermentation time and nutrient sources, with corn steep liquor and NH4Cl emerging as best carbon and nitrogen sources respectively. The study also selected K2HPO4/KH2PO4 (2:1) and 108 cfu/mL as most appropriate phosphate combination and inoculum size respectively for maximum release of protease within the fermentation time of 36 h. One unit of proteolytic activity was defined as the amount of crude enzyme that digested 1 mg of azocasein in one minute under the assay conditions. Assessment of optimum conditions of temperature and pH for test enzyme activity revealed optimum enzyme activity of 158.83 U/mL (2647.70 nkatal) at 40°C and pH 9.0 suggesting protease of the alkaline kind. The enzyme was specific for casein as a protein substrate. Stenotrophomonas acidaminiphila strain BPE4 could be exploited for commercial production of extracellular protease on corn steep liquor as a waste management option and industrial applications.

Stenotrophomonas acidaminiphila, Caseinolytic protease, Production, Corn steep liquor, Environmental factors

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