Characterization and antifungal activity of extracellular β-1,3-glucanase from Paenibacillus polymyxa AT4

Beta-1,3-glucanase is a pivotal enzyme involved in controlling plant pathogens by its contribution to the hydrolytic degradation of β-glucan, one of the major constituents of the fungal cell wall. The objective of this study is to investigate the enzymatic attributes and antifungal efficacy of extracellular β-1,3-glucanase from Paenibacillus polymyxa AT4. The results show that following an 18-hour growth period of the AT4 strain the extracellular β-1,3-glucanase activity reached a maximum value of approximately 2.027 U/mL. Moreover, the optimal activity conditions for the enzyme were determined to be 40°C and 6.0 whereas thermal and pH stability ranged from 30°C to 55°C and 5.0 to 7.0, respectively. The presence of metal ions at 5 mM such as Co2+, Mn2+ and Fe3+ significantly increased β-1,3-glucanase activity up to 118%, 129% and 141% respectively. The inhibitory effects of various compounds including ethylene diamine tetra acetic acid (EDTA), sodium dodecyl sulfate (SDS), urea and triton X-100, on β-1,3-glucanase activity were inhibited. In a controlled in vitro environment, β-1,3-glucanase applied at 0.200 U/mL had a suppressive effect on the growth of Colletotrichum spp., with inhibition levels of approximately 93% for C. scovillei HUD1 and C. fructicola HUCL5, 95% for C. scovillei HUCL1 and C. siamense HUCL3. Besides, β-1,3-glucanase from P. polymyxa AT4 demonstrated a notable ability to mitigate anthracnose development induced by Colletotrichum spp. on chilli fruits for an extended duration of up to 144 h following enzyme pretreatment at 2 U/mL.