Production of Thermostable Alkaline Protease from &lt;i&gt;Streptomyces&lt;/i&gt; sp-A54

O B Okpukpara,U O George-Okafor

doi:10.4314/njb.v31i1.12

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-A2 2 , Micromonospora sp-A2 3 , Streptosporangium A-5 2 , and Streptomyces sp-A5 4 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-A5 4 as the highest producer. Further studies on protease production by Streptomyces sp-A5 4 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 50 0 C. Therefore, the ability of Streptomyces sp-A5 4 to produce thermostable protease at a relatively low concentration indicated its potential as a good source for industrial applications. Keywords - Streptomyces -spA5 4 ,Protease-Fermentation, Optimization, Cultural Condition.

Highlights

Proteases are enzymes that catalyze the hydrolysis of protein into amino-acid
Alkaline proteases produced by microorganisms especially Actinomycetes are of main interest from a biotechnological perspective due to their biochemical diversity and susceptibility to genetic manipulation (Giarrhizo et al, 2007)
Actinomycetes Streptomyces are known to secrete multiple proteases in culture medium which is generally regarded as safe with food and drug administration (Puri et al, 2002)

Summary

Introduction

Proteases are enzymes that catalyze the hydrolysis of protein into amino-acid. Proteases, especially alkaline type constitute about 60-65% of the global industrial enzyme market (Gupta et al, 2010). The study was aimed at selecting an Actinomycetes isolate with protease production potential and optimizing different fermentation parameters for obtaining higher protease yield. Screening for Proteolytic Activity: The identified actinomycetes were plated onto skim milk agar plates and incubated at room temperature for 24-48h. The fermentation broth was centrifuged at 1000revmin-1at 40C for 30min and the recovered clear supernatant used as crude enzyme was concentrated to 10% for protease assay.

Results

Conclusion