Preparation of composites based on herbicide-degrading bacteria and their effects on soil bacterial communities

Abstract

The microbial degradation of atrazine and nicosulfuron residues in soil serves as an effective bioremediation method. In this experiment, three strains capable of degrading atrazine or nicosulfuron were chosen to create a compound microbial inoculant. Chitosan spheres were prepared through acid-base titration for encapsulation, ensuring that the strains can exert a consistent effect during the subsequent crop planting. The verification process confirmed that the encapsulated chitosan-microbial composite retained substantial degradation efficacy on the seventh day, with degradation rates of 82.62 % for atrazine and 65.28 % for nicosulfuron, respectively. Utilizing a neural network-based ANN (artificial neural network) model, it was revealed that the BC composite attained the highest degradation rates, reaching 88.18 % for atrazine and 69.90 % for nicosulfuron. The composite potentially possesses a more robust capability to enhance crop growth. The auxin (IAA) production of the chitosan-microbial composite was measured and found to reach 43.30 mg/L. The introduction of the composite led to an 11.02 % increase in the relative abundance of Proteobacteria. Additionally, the relative abundances of Gemmatimonadota, Chloroflexi, Bacteroidota, Actinobacteriota, and Acidobacteriota exhibited varying degrees of increase. Simultaneously, through the combined action of chitosan and inoculant, there is an enhancement in the microbial community's functions related to energy production and conversion, translation, ribosomal structure, and biogenesis in the soil. This enhancement effectively elevates soil fertility and stimulates crop growth. The findings imply that the chitosan-microbial composite holds promise as a resource for mitigating harmful substances in soil and enhancing soil quality.