Abstract
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.
Highlights
Proteases, variously called peptidases or proteinases, are hydrolytic enzymes belonging to the group of hydrolases (EC 3.4.21-24) which catalyze the hydrolytic cleavage of peptide bonds in proteins and polypeptides releasing peptides of shorter lengths and monomeric amino acid units
We report the potential of Stenotrophomonas acidaminiphila strain BPE4 to elaborate protease and the nutritional and environmental conditions required for production and activity of the enzyme
If the protease was to catalyze the breakdown of a proteolytic substrate to generate simple amino products which would serve as nitrogen source, cellular metabolism would have been delayed in the organism except there was a readily available inorganic nitrogen source in the medium
Summary
Variously called peptidases or proteinases, are hydrolytic enzymes belonging to the group of hydrolases (EC 3.4.21-24) which catalyze the hydrolytic cleavage of peptide bonds in proteins and polypeptides releasing peptides of shorter lengths and monomeric amino acid units. They are synthesized by all life forms including plants (papain, bromelain and ficin), animals (chymosin, trypsin and pepsin) and microorganisms (subtilisin, bacillopeptidases and aspergillopepsin) [12, 15]. We report the potential of Stenotrophomonas acidaminiphila strain BPE4 to elaborate protease and the nutritional and environmental conditions required for production and activity of the enzyme
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