Isolation of Lysinibacillus sp. LL4-1 from plant rhizosphere and synergistic application with plants for formaldehyde indoors removal.

The plant rhizosphere harbors diverse microorganisms, including strains capable of volatile organic compound (VOC) uptake and air purification. This study isolated Lysinibacillus sp. LL4-1, a high-efficiency formaldehyde-degrading bacterium, from the root system of Epipremnum aureum (E. aureum) pre-treated with formaldehyde solution. The Gram-positive, rod-shaped, non-sporulating strain (1000 × 310 nm) demonstrated optimal degradation at pH 7.0, 35 °C, and 150 rpm agitation. Under these conditions, LL4-1 completely metabolized formaldehyde (50-1200 mg/L) in aqueous solutions, with biomass (OD600) increasing proportionally to formaldehyde concentration, peaking at 1.4 for 1200 mg/L at 22 h. When applied as a suspension (OD600 = 0.8) to potted plants E. aureum, Chlorophytum comosum (C. comosum), and Dracaena trifasciata (D. trifasciata), gaseous formaldehyde (5 ppm) removal efficiency significantly improved, particularly in C. comosum (daytime: 27.8 ± 2.03%; nighttime: 16.67% ± 2.52% enhancement). These findings indicate LL4-1's dual capacity for efficient formaldehyde degradation in both aqueous and atmospheric phases, with successful application to phylloplane in host and non-host plants, suggesting promising applications for microbe-plant integrated air remediation systems.