Abstract
This study was conducted to identify a new alkaline and thermophilic protease (Ba.St.Pr) produced from Bacillus stearothermophilus isolated from olive oil mill sols and to evaluate its culture conditions, including temperature, pH, carbon and nitrogen sources, and incubation time. The optimum culture conditions for cell growth (10 g/L) and protease production (5050 U/mL) were as follows: temperature 55 °C, pH 10, inoculation density 8 × 108 CFU/mL, and incubation time 24 h. The use of 3% yeast extract as the nitrogen sources and galactose (7.5 g/L) as the carbon sources enhanced both cell growth and protease production. Using reversed-phase analytical HPLC on C-8 column, the new protease was purified with a molecular mass of approximately 28 kDa. The N-terminal sequence of Ba.St.Pr exhibited a high level of identity of approximately 95% with those of Bacillus strains. Characterization under extreme conditions revealed a novel thermostable and alkaline protease with a half-life time of 187 min when incubated with combined Ca2+/mannitol. Ba.St.Pr demonstrated a higher stability in the presence of surfactant, solvent, and Ca2+ ions. Consequently, all the evaluated activity parameters highlighted the promising properties of this bacterium for industrial and biotechnological applications.
Highlights
Proteases are proteolytic enzymes that decompose proteins by hydrolyzing their peptide bonds
We demonstrate the optimization of culture conditions, purification, and biochemical characterization of a novel thermostable and alkaline protease from Bacillus stearothermophilus isolated from olive oil mill sols and suitable to industrial biotechnology
It is well established that carbon and nitrogen sources significantly affect the cell growth and protease production from bacterial strains
Summary
Proteases are proteolytic enzymes that decompose proteins by hydrolyzing their peptide bonds. Proteases are derived from different sources such as animals, plants, and microorganisms, microbial enzymes are characterized with simple and rapid production, independently of climatic conditions or seasonal changes [1,2,3]. Production of extracellular proteases by microorganisms is more interesting than their intracellular production because this process simplifies the downstream processing, thereby further lowering the costs [4]. The genus Bacillus is the most prominent source among all the investigated bacteria. This finding is related to the high capacity for protein secretion with more than 20 g/L protein [8] and to the production of neutral and alkaline proteases [9,10], which is an interesting aspect for enzyme use in industries [11,12]
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