Isolation of formaldehyde-degrading bacteria and the evaluation of the degradation characteristics

Enhancing the sustainable immobilization of laccase by amino-functionalized PMMA-reinforced graphene nanomaterial

Human health and the environment are negatively affected by endocrine-disrupting chemicals (EDCs), such as bisphenol A. Therefore, developing appropriate remediation methods is essential for efficiently removing phenolic compounds from aqueous solutions. Enzymatic biodegradation is a potential biotechnological approach for responsibly addressing water pollution. With its high catalytic efficiency and few by-products, laccase is an eco-friendly biocatalyst with significant promise for biodegradation. Herein, two novel supporting materials (NH2-PMMA and NH2-PMMA-Gr) were fabricated via the functionalization of poly(methylmethacrylate) (PMMA) polymer using ethylenediamine and reinforced with graphene followed by glutaraldehyde activation. NH2-PMMA and NH2-PMMA-Gr were utilized for laccase immobilization with an immobilization yield (IY%) of 78.3% and 82.5% and an activity yield (AY%) of 81.2% and 85.9%, respectively. Scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) were used to study the characteristics of fabricated material supports. NH2-PMMA-Gr@laccase exhibited an optimal pH profile from 4.5 to 5.0, while NH2-PMMA@laccase exhibited optimum pH at 5.0 compared to a value of 4.0 for free form. A wider temperature ranges of 40-50 °C was noted for both immobilized laccases compared to a value of 40 °C for the free form. Additionally, it was reported that immobilized laccase outperformed free laccase in terms of substrate affinity and storage stability. NH2-PMMA@laccase and NH2-PMMA-Gr@laccase improved stability by up to 3.9 and 4.6-fold when stored for 30 days at 4 °C and preserved up to 80.5% and 86.7% of relative activity after ten cycles of reuse. Finally, the degradation of BPA was achieved using NH2-PMMA@laccase and NH2-PMMA-Gr@laccase. After five cycles, NH2-PMMA@laccase and NH2-PMMA-Gr@laccase showed that the residual degradation of BPA was 77% and 84.5% using 50 μm of BPA. This study introduces a novel, high-performance material for organic pollution remediation in wastewater that would inspire further progress.

Biodegradation enhancement of high concentrations formaldehyde waste gas and verification of the metabolic mechanism

The enhanced effects of formaldehyde biodegradation in a biofilm packing tower are investigated in this study. Three experimental groups were established: a blank control group, a biochar addition group, and a lanthanum addition group. The inlet gas flow rate, the inlet gas concentration, and the structural succession characteristics of the microbial community in the tower were investigated by regular sampling. The intracellular metabolites and key enzymes of the dominant functional bacteria, Pseudomonas P1 and Methylobacterium Q1, in the tower were analyzed. The results indicated that with the biochar addition, the formaldehyde purification efficiency increased significantly from 91.67-94.67 % to 94.12 96.85 %, and the bio-elimination capacity increased with an increase in the inlet gas flow rate from 2.314 to 13.988 mg L-1h-1 to 2.697-15.051 mg L-1h-1. With the addition of lanthanum, the purification efficiency increased significantly from 90.80-93.98 % to 94.36-96.78 %, and the bio-elimination capacity increased with an increase in the inlet gas concentration from 1.099-11.284 mg L-1h-1 to 1.266-11.961 mg L-1h-1. The microbial community structure in the tower changed with system operation, and the formaldehyde degrading functional bacteria formed the dominant bacteria. It was verified that P1 and Q1 metabolized high concentrations of formaldehyde by the serine cycle and the ribulose monophosphate (RuMP) cycle.

Performance evaluation and microbial community analysis of the biofilter for removing grease and volatile organic compounds in the kitchen exhaust fume

Corncob-based activated carbon has very good adsorption performance and can provide a favourable growing environment for microorganisms. In this study, a biofilter packed with corncob-based activated carbon was constructed to remove grease and total volatile organic compounds (TVOCs) in kitchen exhaust fume. Results show that the biofilter was suitable for the biodegradation of grease and VOCs, and the maximum elimination capacities (EC_max) were 112 and 235 g/(m³·h) at an empty bed residence time of 3.24 s, respectively. When the pH of the filler dropped to 5.0 ± 0.2, the removal efficiencies (RE) of grease and TVOCs in the biofilter decreased to the minimum values (75% and 77%, respectively). The REmax were respectively 88 ± 4% (for TVOC) at 70% filler moisture content and 90 ± 3% (for grease) at 76% filler moisture content. Molecular characterization results showed Thermobacillus sp. as dominating microbial group in the packing media.

Preparation and Evaluation of a Composite Filler Micro-Embedded with Pseudomonas putida for the Biodegradation of Toluene : Preparation of composite filler with high toluene removal efficiency

The main objective of this study was to evaluate the performance of a self-developed filler micro-embedded with Pseudomonas putida (P. putida) for toluene removal in a biofilter under various loading rates. The results show that the biofilter could reach 85% removal efficiency (RE) on the eighth day and remain above 90% RE when the empty bed residence time (EBRT) was 18 s and the inlet loading was not higher than 41.4 g m−3 h−1. Moreover, the biofilter could tolerate substantial transient shock loadings. After two shut-down experiments, the removal efficiency could be restored to above 80% after a recovery period of three days and six days, respectively. Sequence analysis of the 16S rRNA gene of fillers in four operating periods revealed that the highly efficient bacterial colonies in fillers mainly included Firmicutes, Actinobacteria and Proteobacteria and that the abundance of Bacteroidetes increased significantly during the re-start period.

Construction of luffa sponge-based magnetic carbon nanocarriers for laccase immobilization and its application in the removal of bisphenol A

The raw material of resin, Bisphenol A (BPA), is an endocrine-disrupting compound that can be continuously released into the environment and directly harms health. In this study, luffa sponge was used as the raw material to prepare magnetic carbon chemicals for laccase immobilization and BPA degradation. The MLC-1 was synthesized by one-step carbonization-magnetization method, which showed good magnetic properties and a strong load capacity for laccase. Compared with free laccase, Laccase@MLC-1 showed stronger thermal stability, better acid-tolerate performance and reusability. Moreover, Laccase@MLC-1 showed higher BPA degradation efficiency than free laccase. 100 mg/L of BPA can be completely removed by Laccase@MLC-1 in 4 h, while only 62.70% of BPA was removed by the same amount of free laccase. By improving reuse strategies, a complete BPA degradation ratio was obtained in each reoperation process. All results proved that Laccase@MLC-1 might be a suitable biocatalyst candidate for BPA removal.

Biotechnology progress for removal of indoor gaseous formaldehyde

Formaldehyde is a ubiquitous carcinogenic indoor pollutant. The treatment of formaldehyde has attracted increasing social attention. Over the past few decades, an increasing number of publications have reported approaches for removing indoor formaldehyde. These potential strategies include physical adsorption, chemical catalysis, and biodegradation. Although physical adsorption is widely used, it does not really remove pollution. Chemical catalysis is very efficient but adds the risk of introducing secondary pollutants. Biological removal strategies have attracted more research attention than the first two methods, because it is more efficient, clean, and economical. Plants and bacteria are the common organisms used in formaldehyde removal. However, both have limitations and shortcomings when used alone. This review discusses the mechanisms, applications, and improvements of existing biological methods for the removal of indoor gaseous formaldehyde. A combination strategy relying on plants, bacteria, and physical adsorbents exhibits best ability to remove formaldehyde efficiently, economically, and safely. When this combination system is integrated with a heating, ventilation, air conditioning, and cooling (HVAC) system, a practical combined system can be established in formaldehyde removal. Multivariate interactions of biological and non-biological factors are needed for the future development of indoor formaldehyde removal. KEY POINTS: • Indoor gaseous formaldehyde removal is necessary especially for new residence. • Biological removal strategies have attracted increasing research attentions. • Combined system of plants, bacteria, and physical adsorbents exhibits best efficiency. • Integrated device of biological and non-biological factors will be potential practical.