Proteolytic activity of alkaliphilic, salt-tolerant actinomycetes from various regions in Saudi Arabia

Actinomycetes were isolated from various desert soil samples of Saudi Arabia using alkaline and normal pH media. A total of 42 akaliphilic actinomycetes isolated from yeast extract-soluble starch (YS) agar media (pH 11.0 ± 1) and 102 actinomycetes were isolated from tap water agar media (pH 7.0 ± 1) for comparison. Aerial mycelium colours of actinomycetes were observed for the detection of strain varieties in the different soil samples from different areas. Colour types were more abundant in isolates grown tap water agar (TWA) than in isolates grown on YS agar medium (pH 11.0). On the TWA medium, there were 18 colour types of actinomycetes and on YS agar medium (pH 11.0) there were 10 colour types. The number of neutrophilic actinomycetes isolated in this study is higher than the alkaliphilic actinomycetes. Among the 42 alkaliphilic actinomycetes isolates, 30 isolates were salt tolerant alkaliphilic. Later about 16 alkaliphilic actinomycetes were screened on skim milk agar for preliminary proteolytic activity. A total of 10 isolates showed proteolytic activity. Of the 10 isolates, three isolates were alkaliphilic and seven isolates were salt-tolerant alkaliphilic. All the isolates need to be further studied for the ability of their potential protease enzyme production.