Bioinspired Green Synthesis of Chitosan and Zinc Oxide Nanoparticles with Strong Antibacterial Activity against Rice Pathogen Xanthomonas oryzae pv. oryzae

Abstract

Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most devastating diseases, resulting in significant yield losses in rice. The extensive use of chemical antibacterial agents has led to an increase the environmental toxicity. Nanotechnology products are being developed as a promising alternative to control plant disease with low environmental impact. In the present study, we investigated the antibacterial activity of biosynthesized chitosan nanoparticles (CSNPs) and zinc oxide nanoparticles (ZnONPs) against rice pathogen Xoo. The formation of CSNPs and ZnONPs in the reaction mixture was confirmed by using UV-vis spectroscopy at 300–550 nm. Moreover, CSNPs and ZnONPs with strong antibacterial activity against Xoo were further characterized by scanning and transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Compared with the corresponding chitosan and ZnO alone, CSNPs and ZnONPs showed greater inhibition in the growth of Xoo, which may be mainly attributed to the reduction in biofilm formation and swimming, cell membrane damage, reactive oxygen species production, and apoptosis of bacterial cells. Overall, this study revealed that the two biosynthesized nanoparticles, particularly CSNPs, are a promising alternative to control rice bacterial disease.

The Bio-Synthesis of Three Metal Oxide Nanoparticles (ZnO, MnO2, and MgO) and Their Antibacterial Activity Against the Bacterial Leaf Blight Pathogen

“…The SEM-EDS shows the elemental analysis of the nanoparticles contained only the element and oxygen which confirms the presence of the nanoparticles in the samples and its high purity. The elemental percentage of ZnONPs in this study is consistent with the reports of Abdallah et al (2020), while those of MnO 2 NPs and MgONPs are in agreement with the report of Ogunyemi et al (2019a). Upon the treatment with ZnO, MgO, or MnO 2 , the characteristic cell damage and leakage of cell content observed using TEM agrees with the reports of Stoimenov et al (2002), who reported the loss of distinctive cell membrane of Escherichia coli.…”

“…The absence of peaks in the bulk solutions of ZnO, MgO, and MnO 2 indicates the absence of nanoparticles in the bulk solutions which is consistent with the reports of Abdallah et al (2020). The UV peak of 385, 230, and 230 nm, respectively, for ZnO, MgO, and MnO 2 nanoparticles recorded in this study is consistent with our previous study of biosynthesis of MgO and MnO 2 nanoparticles (Ogunyemi et al, 2019a), while Abdallah et al (2019bAbdallah et al ( , 2020 recorded a different peak for ZnO and MgO nanoparticles. In the study of Salunke et al (2015), a peak of 365 nm was observed for MnO 2 nanoparticles.…”

“…The average dominant crystallite sizes by the XRD calculated from the diffraction peaks by Scherrer's equation were 62.8, 18.8, and 10.9 nm for ZnONPs, MnO 2 NPs, and MgONPs, respectively, thus, the SEM results are similar with that of XRD. Similar average crystallite size results were reported by Abdallah et al (2020), who synthesized ZnONPs by using green tomato fruits. Also, the results in this study are in agreement with previous study of Ogunyemi et al (2019a), who reported similar average size of 16.5 and 18.2 nm, respectively, for MnO 2 NPs and MgONPs when synthesized by Chamomile flower extract, whereas Salunke et al (2015) reported an higher average size of 34.4 nm for MnO 2 NPs.…”

“…Metabolite lipopeptides from P. polymyxa, which are natural surfactants, acted as a stabilizing agent in silver nanoparticles synthesis and reduced the formation of aggregates due to the electrostatic force of attraction thereby, facilitating uniform morphology of nanoparticles (Kiran et al, 2010;Rangarajan et al, 2018). Diverse shapes of mixed population containing hexagonal, spherical, and disc-shaped have been reported for ZnO, MgO, and MnO 2 nanoparticles (Omid et al, 2014;Sharma P. et al, 2017;Abdallah et al, 2020), while in this study a uniformity in the shapes of the synthesized nanoparticles were reported.…”

“…The synthesis protocol used in this study was adopted because it is cheap and eco-friendly. In addition, the protocol used enhanced the uniformity of shapes of the synthesized nanoparticles as opposed the findings of Abdallah et al (2020), who reported diverse polymorphic shapes. Ogunyemi et al (2019b) assert that the small size of ZnO nanoparticles synthesized by Olive leaves played an important role in the strong antibacterial activity recorded against rice pathogen.…”