Interaction of tetrahydrofuran and methyl tert-butyl ether in waste gas treatment by a biotrickling filter bioaugmented with Piscinibacter caeni MQ-18 and Pseudomonas oleovorans DT4.

Bioaugmented biotrickling filter (BTF) seeded with Piscinibacter caeni MQ-18, Pseudomonas oleovorans DT4, and activated sludge was established to investigate the treatment performance and biodegradation kinetics of the gaseous mixtures of tetrahydrofuran (THF) and methyl tert-butyl ether (MTBE). Experimental results showed an enhanced startup performance with a startup period of 9 d in bioaugmented BTF (25 d in control BTF seeded with activated sludge). The interaction parameter I2,1 of control (7.462) and bioaugmented BTF (3.267) obtained by the elimination capacity-sum kinetics with interaction parameter (EC-SKIP) model indicated that THF has a stronger inhibition of MTBE biodegradation in the control BTF than in the bioaugmented BTF. Similarly, the self-inhibition EC-SKIP model quantified the positive effects of MTBE on THF biodegradation, as well as the negative effects of THF on MTBE biodegradation and the self-inhibition of MTBE and THF. Metabolic intermediate analysis, real-time quantitative polymerase chain reaction, biofilm-biomass determination, and high-throughput sequencing revealed the possible mechanism of the enhanced treatment performance and biodegradation interactions of MTBE and THF.

Enhanced biodegradation of n-hexane in a two-phase partitioning bioreactor inoculated with Pseudomonas mendocina NX-1 under chitosan stimulation.

Two-phase partitioning bioreactors (TPPBs) have been extensively used for volatile organic compounds (VOCs) removal. To date, most studies have focused on improving the mass transfer of gas phases/non-aqueous phases (NAPs)/aqueous phases, whereas the NAP/biological phases and gas/biological phases transfer has been neglected. Herein, chitosan was introduced into a TPPB to increase cell surface hydrophobicity (CSH) and improve the n-hexane mass transfer. The performance and stability of the TPPB with chitosan for n-hexane biodegradation were investigated, and it was found out that the TPPB with chitosan achieved maximum removal efficiency and elimination capacity of 80.6% and 26.5 g m-3 h-1, thereby reaching much higher values than those obtained without chitosan (61.3% and 15.2 g m-3 h-1). Chitosan not only obvio usly increased cell surface hydrophobicity and cell dry biomass on the surface of silicone oil, but might also allow hydrophobic cells in aqueous phases to directly capture and biodegrade n-hexane, resulting in an obvious improvement of mass transfer from the gas phase to biomass. Stability enhancement was another attractive advantage from chitosan addition. This study might provide a new strategy for the development of TPPB in the hydrophobic VOCs treatment.

Removal of gaseous tetrahydrofuran via a three-phase airlift bioreactor loaded with immobilized cells of GFP-tagged Pseudomonas oleovorans GDT4.

Tetrahydrofuran (THF) is a common highly toxic cyclic aliphatic ether that frequently exists in waste gases. Removal of gaseous THF is a serious issue with important environmental ramifications. A novel three-phase airlift bioreactor (TPAB) loaded with immobilized cells was developed for efficient THF removal from gas streams. An effective THF-degrading transformant, Pseudomonas oleovorans GDT4, which contains the pTn-Mod-OTc-gfp plasmid and was tagged with a green fluorescent protein (GFP), was constructed. Continuous treatment of THF-containing waste gases was succeeded by the GFP-labelled cells immobilized with calcium alginate and activated carbon fiber in the TPAB for 60 days with >90% removal efficiency. The number of fluorescent cells in the beads reached 1.7 × 1011 cells·g-1 of bead on day 10, accounting for 83.3% of the total number of cells. The amount further increased to 3.0 × 1011 cells·g-1 of bead on day 40. However, it decreased to 2.5 × 1011 cells·g-1 of bead with a substantial increase in biomass in the liquid because of cell leakage and hydraulic shock. PCR-DGGE revealed that P. oleovorans was the dominant microorganism throughout the entire operation. The maximum elimination capacity was affected by empty bed residence time (EBRT). The capacity was only 25.9 g m-3·h-1 at EBRT of 80 s, whereas it reached 37.8 g m-3·h-1 at EBRT of 140 s. This work provides an alternative method for full-scale removal of gaseous THF and presents a useful tool for determining the biomass of a specific degrader in immobilized beads.

Enhancing Chlorobenzene Biodegradation by Delftia tsuruhatensis Using a Water-Silicone Oil Biphasic System.

In this study, a water-silicone oil biphasic system was developed to enhance the biodegradation of monochlorobenzene (CB) by Delftia tsuruhatensis LW26. Compared to the single phase, the biphasic system with a suitable silicone oil fraction (v/v) of 20% allowed a 2.5-fold increase in the maximum tolerated CB concentration. The CB inhibition on D. tsuruhatensis LW26 was reduced in the presence of silicone oil, and the electron transport system activity was maintained at high levels even under high CB stress. Adhesion of cells to the water-oil interface at the water side was observed using confocal laser scanning microscopy. Nearly 75% of cells accumulated on the interface, implying that another interfacial substrate uptake pathway prevailed besides that initiated by cells in the aqueous phase. The 8-fold increase in cell surface hydrophobicity upon the addition of 20% (v/v) silicone oil showed that silicone oil modified the surface characteristics of D. tsuruhatensis LW26. The protein/polysaccharide ratio of extracellular polymeric substances (EPS) from D. tsuruhatensis LW26 presented a 3-fold enhancement. These results suggested that silicone oil induced the increase in the protein content of EPS and rendered cells hydrophobic. The resulting hydrophobic cells could adhere on the water-oil interface, improving the mass transfer by direct CB uptake from silicone oil.

[Preparation of a Nutritional Slow-release Packing Material with Function Microorganisms and Its Characteristics Evaluation].

A nutritional slow-release packing material with function microorganisms (SC) was prepared using emulsification and the cross-linked method. Its potential as packing material in biotrickling filters (BTF) for butyl acetate removal was evaluated. The physicochemical properties show that the packing has a porosity of 92.6%, bulk density of 40.75 kg·m-3, surface area of 2.45 m2·g-1, and real density of 551.52 kg·m-3. The packing material contains hydrophilic groups (O-H, C O) on its surface and nutrient elements (N, P), which are distributed uniformly, with release rates of 22.35 and 8.36 mg·(L·d)-1, respectively. The biomass concentration of the packing (protein/packing) is 14.61 mg·g-1. After storage for 7 and 30 d, the microorganisms fixed on the packing material could still remove more than 96% of butyl acetate. The BTF using SC as packings reach stable performance within a short time (8 d) and the removal efficiency is maintained at 94% unless there nutrition is supplied or the pH is adjusted. The BTF with polyurethane as packing material need a longer time to start up and the removal efficiency decreases to 80% under the same operating conditions. High-throughput sequencing analysis shows that the fixed degrading stains are dominant during the whole operation and the microbial structure is more stable, which could sustain the stable removal of butyl acetate in BTF using SC.

Piscinibacter caeni sp. nov., isolated from activated sludge.

A yellowish-pigmented bacterial strain, designated as MQ-18T, was isolated from a sample of activated sludge collected from a pharmaceutical factory in Zhejiang, China. The strain was characterized through a polyphasic taxonomy approach. 16S rRNA gene sequence analysis demonstrated that strain MQ-18T showed high similarities to Piscinibacter defluvii SH-1T (99.7 %) and Piscinibacter aquaticus IMCC1728T (98.4 %), thereby suggesting that it belongs to the genus Piscinibacter. The DNA-DNA relatedness values of this strain to strains SH-1T and IMCC1728T were only 35.4 and 33.3 %, respectively. Cells of MQ-18T were Gram-negative, aerobic, motile, rod-shaped and non-spore forming. This strain exhibited growth at 25-37 °C (optimum: 30 °C) in the presence of 0-3.0 % (w/v) NaCl (optimum, 0 % NaCl) and at pH 5.0-8.0 (pH 7.0). The predominant fatty acids were C12 : 0 (5.5 %), C16 : 0 (33.7 %), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c; 38.5 %), and summed feature 4 (anteiso-C17 : 1 B and/or iso C17 : 1 I; 11.6 %). The main quinone type was ubiquinone-8, and the major polyamines were cadaverine and putrescine. The major polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The DNA G+C content was 70.1 mol%. On the basis of its phylogenetic, phenotypic and physiological characteristics, strain MQ-18T is considered to represent a novel species of the genus Piscinibacter, for which the name Piscinibacter caeni sp. nov. is proposed. The type strain is MQ-18T (CCTCC AB 2017223T=JCM 32138T).

A solid composite microbial inoculant for the simultaneous removal of volatile organic sulfide compounds: Preparation, characterization, and its bioaugmentation of a biotrickling filter.

Volatile organic sulfide compounds (VOSCs) are usually resistant to biodegradation, thereby limiting the performance of traditional biotechnology dealing with waste gas containing such pollutants especially in mixture. In this study, a solid composite microbial inoculant (SCMI) was prepared to remove dimethyl sulfide (DMS) and propanethiol (PT). Given that the DMS degradation activity of Alcaligenes sp. SY1 is inducible and the PT-degradation activity of Pseudomonas putida S-1 is constitutive, different strategies are designed for cell cultivation to obtain high VOSC removal rates of SCMI. Compared with the microbial suspension, the prepared SCMI exhibited better storage stability at 4 and 25°C. Inoculation of the SCMI in biotrickling filters (BTFs) could effectively shorten the start-up period and enhance the removal performance. Microbial analysis by Illumina MiSeq indicated that Alcaligenes sp. SY1 and P. putida S-1 might be dominant and persistent among the microbial communities of the BTF during the operation.

Comparative investigation on a hexane-degrading strain with different cell surface hydrophobicities mediated by starch and chitosan.

Bioremediation usually exhibits low removal efficiency toward hexane because of poor water solubility, which limits the mass transfer rate between the substrate and microorganism. This work aimed to enhance the hexane degradation rate by increasing cell surface hydrophobicity (CSH) of the degrader, Pseudomonas mendocina NX-1. The CSH of P. mendocina NX-1 was manipulated by treatment with starch and chitosan solution of varied concentrations, reaching a maximum hydrophobicity of 52%. The biodegradation of hexane conformed to the Haldane inhibition model, and the maximum degradation rate (ν max) of the cells with 52% CSH was 0.72 mg (mg cell)-1·h-1 in comparison with 0.47 mg (mg cell)-1·h-1 for cells with 15% CSH. The production of CO2 by high CSH cells was threefold higher than that by cells at 15% CSH within 30 h, and the cumulative rates of O2 consumption were 0.16 and 0.05 mL/h, respectively. High CSH was related to low negative charge carried by the cell surface and probably reduced the repulsive electrostatic interactions between hexane and microorganisms. The FT-IR spectra of cell envelopes demonstrated that the methyl chain was inversely proportional to increasing CSH values, but proteins exhibited a positive effect to CSH enhancement. The ratio of extracellular proteins and polysaccharides increased from 0.87 to 3.78 when the cells were treated with starch and chitosan, indicating their possible roles in increased CSH.

[Removal of Mixed Waste Gases by a Biotrickling Filter Packed with a Novel Combined Packing Material].

A pilot biotrickling filter (BTF) was set up for removal of a mixed waste gas containing toluene and ethanol. The packing material was composed of polyhedral sphere and polyhedral hollow column previously designed by our group. The results showed this BTF could successfully start up within only 8 d and the average eliminate capacities for toluene and ethanol were 97.14 and 113.10 g · (m³ · h)⁻¹, respectively. Empty bed residence time (EBRT) and the inlet concentration had effects on the removal of toluene. The maximum elimination capacity of toluene and ethanol was 123.34 and 206.36 g (m³ · h)⁻¹ under EBRT of 21.11 s, respectively. However, the effect of spray liquid density was not obvious, and the optimal value of solution and gas ratio was 6.82 L · m⁻³. The influence of unstable processing condition on its performance was also investigated. NaOH solution could effectively reduce the plugging of the filler layer, and the removal capability of pollutant could be recovered within 3 days. After the running was stopped for 10 d, the removal performance of this BTF could be quickly recovered.

Photocatalytic conversion of gaseous ethylbenzene on lanthanum-doped titanium dioxide nanotubes.

The photocatalytic properties of titanium dioxide (TiO2) make it an attractive material for environmental remediation. In the present study, lanthanum (La(3+))-doped TiO2 nanotubes with excellent photocatalytic activity were fabricated by a combination of sol-gel method and hydrothermal technique. The optimal preparation parameters were determined by the structural characterization using a range of methods and the photocatalytic degradation of gaseous ethylbenzene (EB). Compared with pure TiO2 nanoparticles, 1.2%-La(3+)-doped - titania nanotubes (1.2%-La(3+)-TNTs) exhibited higher activity under 254 nm UV for conversion of EB. The initial EB concentrations and relative humidity (RH) obviously influenced the photocatalytic activity of 1.2%-La(3+)-TNTs. Kinetic analysis showed that surface adsorption and surface reaction controlled the rate-determining step for RH of 40-50% and >80%, respectively. Gas chromatography and mass spectrometry were used to analyze the intermediates generated in the conversion of EB, allowing a tentative decomposition pathway to be proposed. The prepared photocatalyst exhibited enhanced EB conversion compared with undoped TiO2, and showed a promise for the decomposition of recalcitrant compounds before subsequent biopurification.