Long-term biofiltration of gaseous N,N-dimethylformamide: Operational performance and microbial diversity analysis at different conditions

NLRP3 inflammasome activation triggers severe inflammatory liver injury in N, N-dimethylformamide-exposed mice

N,N-dimethylformamide (DMF) is a widely utilized chemical solvent with various industrial applications. Previous studies have indicated that the liver is the most susceptible target to DMF exposure, whereas the underlying mechanisms remain to be elucidated. This study aimed to investigate the role of NLRP3 inflammasome in DMF-induced liver injury in mice by using two NLRP3 inflammasome inhibitors, Nlrp3-/- mice, Nfe2l2-/- mice, and a macrophage-depleting agent. RNA sequencing revealed that endoplasmic reticulum (ER) stress and NLRP3 inflammasome-associated pathways were activated in the mouse liver after acute DMF exposure, which was validated by Western blotting. Interestingly, DMF-induced liver injury was effectively suppressed by two inflammasome inhibitors, MCC950 and Dapansutrile. In addition, knockout of Nlrp3 markedly attenuated DMF-induced liver injury without affecting the metabolism of DMF. Furthermore, silencing Nfe2l2 aggravated the liver injury and the NLRP3 inflammasome activation in mouse liver. Finally, the depletion of hepatic macrophages by clodronate liposomes significantly reduced the liver damage caused by DMF. These results suggest that NLRP3 inflammasome activation is the upstream molecular event in the development of acute liver injury induced by DMF.

Addition of (bio)surfactants in the biofiltration of hydrophobic volatile organic compounds in air

The removal of volatile organic compounds (VOCs) in air is of utmost importance to safeguard both environmental quality and human well-being. However, the low aqueous solubility of hydrophobic VOCs results in poor removal in waste gas biofilters (BFs). In this study, we evaluated the addition of (bio)surfactants in three BFs (BF1 and BF2 mixture of compost and wood chips (C + WC), and BF3 filled with expanded perlite) to enhance the removal of cyclohexane and hexane from a polluted gas stream. Experiments were carried out to select two (bio)surfactants (i.e., Tween 80 and saponin) out of five (sodium dodecyl sulfate (SDS), Tween 80, surfactin, rhamnolipid and saponin) from a physical-chemical (i.e., decreasing VOC gas-liquid partitioning) and biological (i.e., the ability of the microbial consortium to grow on the (bio)surfactants) point of view. The results show that adding Tween 80 at 1 critical micelle concentration (CMC) had a slight positive effect on the removal of both VOCs, in BF1 (e.g., 7.0 ± 0.6 g cyclohexane m-3 h-1, 85 ± 2% at 163 s; compared to 6.7 ± 0.4 g cyclohexane m-3 h-1, 76 ± 2% at 163 s and 0 CMC) and BF2 (e.g., 4.3 ± 0.4 g hexane m-3 h-1, 27 ± 2% at 82 s; compared to 3.1 ± 0.7 g hexane m-3 h-1, 16 ± 4% at 82 s and 0 CMC), but a negative effect in BF3 at either 1, 3 and 9 CMC (e.g., 2.4 ± 0.4 g hexane m-3 h-1, 30 ± 4% at 163 s and 1 CMC; compared to 4.6 ± 1.0 g hexane m-3 h-1, 43 ± 8% at 163 s and 0 CMC). In contrast, the performance of all BFs improved with the addition of saponin, particularly at 3 CMC. Notably, in BF3, the elimination capacity (EC) and removal efficiency (RE) doubled for both VOCs (i.e., 9.1 ± 0.6 g cyclohexane m-3 h-1, 49 ± 3%; 4.3 ± 0.3 g hexane m-3 h-1, 25 ± 3%) compared to no biosurfactant addition (i.e., 4.5 ± 0.4 g cyclohexane m-3 h-1, 23 ± 3%; hexane 2.2 ± 0.5 g m-3 h-1, 10 ± 2%) at 82 s. Moreover, the addition of the (bio)surfactants led to a shift in the microbial consortia, with a different response in BF1-BF2 compared to BF3. This study evaluates for the first time the use of saponin in BFs, it demonstrates that cyclohexane and hexane RE can be improved by (bio)surfactant addition, and it provides recommendations for future studies in this field.

Effect of inoculum type, packing material and operational conditions on the biofiltration of a mixture of hydrophobic volatile organic compounds in air

The emission of volatile organic compounds (VOCs) into the atmosphere causes negative environmental and health effects. Biofiltration is known to be an efficient and cost-effective treatment technology for the removal of VOCs in waste gas streams. However, little is known on the removal of VOC mixtures and the effect of operational conditions, particularly for hydrophobic VOCs, and on the microbial populations governing the biofiltration process. In this study, we evaluated the effect of inoculum type (acclimated activated sludge (A-AS) versus Rhodococcus erythropolis) and packing material (mixture of compost and wood chips (C + WC) versus expanded perlite) on the removal of a mixture of hydrophobic VOCs (toluene, cyclohexane and hexane) in three biofilters (BFs), i.e., BF1: C + WC and R. erythropolis; BF2: C + WC and A-AS; and BF3: expanded perlite and R. erythropolis. The BFs were operated for 374 days at varying inlet loads (ILs) and empty bed residence times (EBRTs). The results showed that the VOCs were removed in the following order: toluene > cyclohexane > hexane, which corresponds to their air-water partitioning coefficient and thus bioavailability of each VOC. Toluene is the most hydrophilic VOC, while hexane is the most hydrophobic. BF2 outperformed BF1 and BF3 in each operational phase, with average maximum elimination capacities (ECmax) of 21 ± 3 g toluene m-3 h-1 (removal efficiency (RE): 100 %; EBRT: 82 s), 11 ± 2 g cyclohexane m-3 h-1 (RE: 86 ± 6 %; EBRT: 163 s) and 6.2 ± 0.9 g hexane m-3 h-1 (RE: 96 ± 4 %; EBRT: 245 s). Microbial analysis showed that despite having different inocula, the genera Rhodococcus, Mycobacterium and/or Pseudonocardia dominated in all BFs but at different relative abundances. This study provides new insights into the removal of difficult-to-degrade VOC mixtures with limited research to date on biofiltration.

Allyl methyl disulfide (AMDS) prevents N,N-dimethyl formamide-induced liver damage by suppressing oxidative stress and NLRP3 inflammasome activation

N,N-dimethylformamide (DMF), a widely consumed industrial solvent with persistent characteristics, can induce occupational liver damage and pose threats to the general population due to the enormous DMF-containing industrial efflux and emission from indoor facilities. This study was performed to explore the roles of allyl methyl disulfide (AMDS) in liver damage induced by DMF and the underlying mechanisms. AMDS was found to effectively suppress the elevation in the liver weight/body weight ratio and serum aminotransferase activities, and reduce the mortality of mice induced by DMF. In addition, AMDS abrogated DMF-elicited increases in malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) levels and decreases in glutathione (GSH) levels in mouse livers. The increase in macrophage number, mRNA expression of M1 macrophage biomarkers, and protein expression of key components in the NF-κB pathway and NLRP3 inflammasome induced by DMF exposure were all suppressed by AMDS in mouse livers. Furthermore, AMDS inhibited DMF-induced cell damage and NF-κB activation in cocultured AML12 hepatocytes and J774A.1 macrophages. However, AMDS per se did not significantly affect the protein level and activity of CYP2E1. Collectively, these results demonstrate that AMDS effectively ameliorates DMF-induced acute liver damage possibly by suppressing oxidative stress and inactivating the NF-κB pathway and NLRP3 inflammasome.