Stability studies of cuticle degrading and mycolytic enzymes of <em>Myrothecium verrucaria</em> for control of insect pests and fungal phytopathogens

Abstract

<em>Myrothecium verrucaria</em> produced extracellularly hydrolytic enzymes which can hydrolyse the insect cuticle as well as fungal cell wall. The addition of polyols, such as glycerol, sorbitol, xylitol (1 M) during ultra-filtration or freeze- drying of enzyme mixture increased the recovery of the enzymes in a concentrated form. Polyols (5 M) increased the temperature and pH stability of the enzymes, in the presence of glycerol chitinase , β-1,3-glucanase, lipase and protease retained 50-60% of initial activities at 40°C after 3 h. While xylitol (5 M) was effective in stabilizing activities at pH 5.0 and 7.5 at 25°C for 7 d. In the freeze-dried powder form, > 90% at 4°C for 1 year and 80-85% at 25°C for 2 months enzyme activities were retained. The addition of glycerol (1 M) to the enzyme mixture protected enzyme activities under sunlight (60-65% activity at RT) for 5 d. Because of glycerol (1 M), the efficacy of <em>M. verrucaria </em> enzyme preparation to control <em>Helicoverpa armigera</em> infestation in chick pea was increased to 70 ± 19%. While without glycerol the efficacy was 55 ± 23%. The germination of peanut seeds infected with <em>Sclerotium rolfsii</em> was observed to be increased (70 ± 5%) in a pot irrigated with enzyme mixture.