Characterization of modified rice straw biochar in immobilizing Bacillus subtilis 168 and evaluation on its role as a novel agent for zearalenone-removal delivery

Microbial remediation of environmental pollutants can be advanced by carrier based cells immobilization. Whereas the effects of microorganisms immobilized on biochar for removal of zearalenone (ZEN) still remain unknown. Herein, this work presented the characterization of rice straw biochar (RSB) around modification in immobilizing Bacillus subtilis 168 and the role in fighting ZEN in vitro. Specifically, 10% of RSB with pH 5 condition were optimal for bearing cells, where majority of cells loaded inside the pore and minority on surface with agglomeration or scattering status. Octadecyl trimethyl ammonium chloride-inclusion RSB showed better performances including over 93% of ZEN detoxification rate (32.48% in free cells), cells preservation, and stability of detoxification in simulated gastrointestinal environment. RSB treated with sulphuric acid made nutrients adsorption generally less than 6.5%. No residues of α-ZEL and α-ZAL were found in ZEN biotransformation process whether by free cells or composites. Mechanism discussion implied that predominant monolayer chemisorption by RSB and subsequent biodegradation by extracellular enzymes from microorganism involved in ZEN-removal process. Collectively, these findings contribute to provide an applying strategy for coordination of biochar and microorganisms as potentially mycotoxin detoxifying agent in agricultural feed bioremediation and environmental decontamination processes.