Mycolytic enzymes produced by Streptomyces violaceusniger and their role in antagonism towards wood‐rotting fungi

Abstract

Extracellular mycolytic enzymes produced under submerged fermentation by the fungal antagonist Streptomyces violaceusniger MTCC 3959 were characterized. This streptomycete produced higher amounts of extracellular chitinase and protease during late exponential phase, whereas β-1,3-glucanase production was at peak in mid-stationary phase. Cell-free culture filtrate (CCF) exhibited a broad range of antifungal activity against both white rot and brown rot fungi. The inhibitory activity was completely lost after treatment with proteinase K and heat, indicating that extracellular antifungal metabolites are heat labile and proteinaceous in nature. Optimum pH and temperature for enzyme activity were: 9.0 and 60 °C for chitinase; 6.0 and 60 °C for β-1,3-glucanase; and 9.0 and 70 °C for protease. Mycolytic enzymes were moderately thermostable, and had a wide pH stability range extending from pH 5.0 to 10.0. The zymogram analysis of CCF revealed five chitinase isoenzymes with an apparent molecular weight of 20.8, 33.3, 45.6, 67.4, and 114.8 kDa, one β-1,3-glucanase appeared as a single band of ∼131.8 kDa and four protease isoenzymes with approximate molecular weights of 22.8, 62.52, 74.64, and 120.5 kDa. S. violaceusniger MTCC 3959 produced mycolytic enzymes that can be effectively used for suppression of phytopathogenic basidiomycetes. It has the potential to be an effective biofungicide.

Fungal cell-wall lytic enzymes, antifungal metabolite(s) production, and characterization fromStreptomyces exfoliatusMT9 for controlling fruit-rotting fungi

“…Antifungal potential of the CCF was due to heat‐sensitive proteins such as extracellular mycolytic enzymes, namely chitinase, β‐1,3‐glucanase, and protease. These results were in agreement with the study of Nagpure et al .…”

“…The occurrence of several isoenzymes of chitinase from Streptomyces sp. was also previously reported [16,43]. The optimum pH and temperature of protease was found to be 9.0 and 70°C, respectively which is similar to that of protease from antagonist S. violaceusniger MTCC 3959 [16].…”

“…The result indicates that strong inhibition showed by S. exfoliatus MT9 is probably due to the release of an extracellular diffusible metabolite(s), antifungal compounds, and other cell‐wall lytic enzymes essential for fungal cell‐wall degradation. Several previous reports also suggest that the antagonistic activity of Streptomyces to numerous phytopathogenic fungi involves the production of antifungal secondary metabolite(s) and extracellular hydrolytic enzymes .…”

Root Associated Bacillus sp. Improves Growth, Yield and Zinc Translocation for Basmati Rice (Oryza sativa) Varieties

“…These metabolites include siderophores which chelate iron and deprive the pathogen from an important source of nutrition, thereby inhibiting the pathogen by creating a competitive environment (Aznar and Dellagi, 2015 ). The strains also produce hydrolytic enzymes like glucanase, cellulase and protease which hydrolyze the various components of cell wall, thereby paralyzing the pathogen which ultimately leads to death of the pathogen (Nagpure et al, 2014 ). Thus, Zn solubilizing rhizobacteria exhibit multiple PGP traits in vitro which are similar to the earlier findings (El-Sayed et al, 2014 ; Abaid-Ullah et al, 2015 ).…”

“…Development of halo zone around the colonies indicated enzyme production. Zone of exo β-1, 3-glucanase was observed after staining with congo red (Nagpure et al, 2014 ).…”