Abstract
Chitinases which degrade chitin have attracted attention as biological antifungal agents. The purpose of this study is to isolate Streptomyces from Fadama soil and assess its chitinolytic and antagonist potential against phytopathogenic fungi for application as biocontrol agent. Streptomyces were isolated from Fadama soil. The selected isolate CT02 exhibited chitinolytic characteristics. Chitinase production was performed under different temperatures, pH and varying incubation period. The highest chitinase production by CT02 isolate was observed after five days of cultivation. The highest chitinase activity was observed at 35°C and pH 7. The crude extracellular enzyme exhibited a specific activity of 4.20 U/μg whereas partially purified extracellular enzyme exhibited a specific activity of 6.19 U/μg with purification fold of 1.47. The selected isolate CT02 and its extracellular crude chitinase showed in vitro antifungal antagonist potential by inhibiting the growth of Aspergillus niger and Aspergillus oryzae. This indicates that Streptomyces derived chitinases are potential biocontrol agents against phytopathogenic fungi.
Highlights
The Gram-positive actinomycetes are aerobic bacteria that have high GC content in their genome and are good sources of secondary metabolites (Berdy 2005)
Streptomyces were screened for chitinolytic activity and the strain that exhibited the highest chitinase production was identified based on the clear zone of hydrolysis of chitin on colloidal chitin plates [Fig. 1(C)], this strain was selected for further studies
Isolation of chitinase producing actinobacteria from these ecosystems is interesting in order to identify bacteria with a unique metabolism that arise as a result of adaptation to changes in the condition of temperatures in those climates
Summary
The Gram-positive actinomycetes are aerobic bacteria that have high GC content in their genome and are good sources of secondary metabolites (Berdy 2005). Streptomyces in particular is the major producer of commercially important biomolecules (Aggarwal et al 2016). Streptomyces are diverse, they have high rate of metabolic production and play an important role in organic matter recycling as well as being capable of degrading chitin and lignocelluloses (Khanna et al 2011). Chitin is a polymer of N-acetyl glucosamine and one of the most abundant biomaterials in nature. It is the common structural polysaccharide in exo-skeleton of insects and crustaceans and as the major component of fungal cell wall (Shinya & Fukamizo 2017). More attention is given to chitinases due to their potential as eco-friendly and safe biocontrol agents (Gupta et al 1995; Cletus et al 2013; Hammami et al 2013; Awad et al 2014; Nagpure et al 2014)
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