Evaluation of enzyme production and biocontrol agent of zinc nanoparticles from Gonatorrhodiella parasitica

Abstract

Background and objectives Biosynthesis of zinc nanoparticles (Zn NPs) is considered one of the new approaches for enzyme production and good biofertilizer and biocontrol agent for pathogenic disease of plant. The selected fungal strain Gonatorrhodiella parasitica was used for biosynthesis of Zn NPs. Determination of enzyme activity in fermentation medium containing olive mill wastes (OMW) as substrate for production of protease, pectinase, and chitinase at different pH values (6) was done to produce detailed information on the progress of reduction of zinc nitrate on the nanosecond times (6.0, 8.0, and 10.0). Absorbance ultraviolet–visible spectra of Zn NPs at pH 6.0 were at λmax 280 nm. Transmission electron spectroscopy measurements indicate that extracellular biosynthesis of Zn NPs by G. parasitica was in the size of 16 nm. Composting of OMW inoculated with G. parasitica for 15–30 days led to decrease in total phenol, flavonoids, 2,2 diphenyl-1-picrylhydrazyl (DPPH), and aflatoxins found in OMW. Comparison of G. parasitica free and nano zinc particles as biocontrol agent of soil-borne fungi causing preemergence and postemergence damping off of green bean plants (seed treatment) under field conditions measured from 7 to 60 days and its effect of growth parameters confirm the use of Zn NPs for enzymes production and biocontrol application. Materials and methods The local fungal strain G. parasitica used in this study was isolated from soil and identified at the Department of Chemistry of Natural and Microbial Products at the National Research Center. Determination of enzymes activity (pectinase, chitinase and protease) was done. Determination of major phytochemicals in prepared extracts (total phenolic content, total flavonoid content, DPPH scavenging activity, and aflatoxin) was done. A field experiment was conducted during the 2018 season at Kafer-Eldawar (Behira) Governorate, in a heavily naturally infested field, to study the effect of free and Zn NPs of G. parasitica on soil-borne fungi causing preemergence and postemergence damping off of green bean plants (seed treatment) under field conditions. Results and conclusion Composting of OMW inoculated with G. parasitica for 15–30 days led to decrease in total phenol, flavonoids, DPPH, and aflatoxins found in OMW. Moreover, suppressive soil-borne fungi caused preemergence and postemergence root rot of green bean plants (seed treatment) under field conditions.