Production of Thermostable Alkaline Protease from <i>Streptomyces</i> sp-A54

Abstract

Bacterial extracellular alkaline proteases have been found to have broad spectrum industrial applications because of their stability characteristics among the bacteria. The Actinomyces are of enormous importance as they can be recovered easier than other bacteria after fermentation. Thus, the study was aimed at sourcing for potential protease producers among the Actinomycetes species and determining the cultural conditions for their optimal protease yields. Among 67% of the recovered soil isolates that demonstrated potentials for protease production on skimmed milk agar, only Norcardia sp-A2², Micromonospora sp-A2³, Streptosporangium A-5², and Streptomyces sp-A5⁴ produced protease with higher activity(18.5-20.5mm) than the others (8.5-16.5mm). Preliminary protease assay in submerged shake-flask fermentation confirmed Streptomyces sp-A5⁴ as the highest producer. Further studies on protease production by Streptomyces sp-A5⁴ showed that maximum protease yield was achieved within 72h at 0.4% inoculum concentration. All the test organic carbon and nitrogen substrates supported protease yield (> 1.5/2.0 u/ml) but soybean and sweet potato meal gave the highest support (> 2.5/2.53 u/ml). However, their protease yields were significantly (p< 0.05) less than that of refined glucose and peptone when substituted as the carbon and nitrogen sources. The produced crude enzyme demonstrated optimal activity at pH 8.0 and temperature of 50⁰C. Therefore, the ability of Streptomyces sp-A5⁴ to produce thermostable protease at a relatively low concentration indicated its potential as a good source for industrial applications.

Keywords-Streptomyces-spA5⁴,Protease-Fermentation, Optimization, Cultural Condition.