Toxicity treatment of tobacco wastes using experimental design by filamentous fungi

Biochar loaded with nicotine-degrading bacteria works synergistically with native microorganisms to efficiently degrade nicotine

Nicotine, a potential environmental pollutant that has raised increasing concerns, accumulates to significant levels in soils under long-term tobacco monoculture, posing substantial risks to both local ecosystems and human health. Addressing this challenge, the screening and utilization of nicotine-degrading bacteria have emerged as a central remediation strategy. In this study, we isolated nicotine-degrading bacteria from tobacco-cultivated soils and subsequently immobilized them onto biochar to optimize degradation efficiency. A systematic investigation was conducted to examine the synergistic effects and underlying degradation mechanisms of the biochar-bacteria complex. Notably, we successfully isolated Paenarthrobacter ureafaciens N21 (N21), a bacterial strain capable of degrading nicotine through the pyridine pathway. When immobilized on biochar (BN21), the composite maintained robust degradation capabilities in both culture media and soil environments. Compared with free N21, BN21 demonstrated a 1.4 times enhancement in nicotine degradation efficiency and significantly improved colonization capacity by the degrading bacteria (P < 0.0001). Stability assessment tests further confirmed BN21's consistent degradation performance under diverse environmental conditions. Integrated microbiomic and metabolomic analyses revealed that BN21 induced significant alterations in soil microbial community structure and metabolic profiles, while enhancing the soil's resistance to repeated nicotine disturbances. Importantly, BN21 facilitated synergistic interactions between nicotine-degrading bacteria and indigenous microorganisms, collectively mediating nicotine decomposition through coordinated pyridine and pyrrolidine pathways. The novel discovery of bacteria-loaded biochar synergistically enhancing nicotine removal highlights the potential of biochar-microbe composites for targeted pollutant elimination. This approach shows promising prospects for future applications in ecological remediation of various organic contaminants, providing innovative perspectives for developing microbiome-based green remediation strategies.

Toxicity and physicochemical parameters of composts including distinct residues from agribusiness and slaughterhouse sludge

Composting is useful for treatment of residues from agribusiness, but the potential toxicity of the final compost should be evaluated before its agricultural destination. The objective of this study was to evaluate the physicochemical characteristics and the toxicity of agribusiness residues using onion seeds as bioindicators. All tested treatments were composed by sludge from a swine slaughterhouse and sawdust. Besides the control, which included no additional materials, the other treatments included aviary bedding, rice husk and residue from tobacco industries as structuring materials. After 120 days of composting, for all treatments, the temperature inside the composting piles approached the environmental temperature, the physicochemical parameters indicated that the composts were stabilized and, except for the treatment including tobacco residues, that could be used for agriculture without impairing plant germination. Although the treatments including tobacco residues and rice husk showed evidence of cytotoxicity and genotoxicity at the beginning of the composting period, that was not observed for the treatment including aviary bedding. Such potential toxicity was not observed at the end of composting for any of the tested treatments.