Implementation of a botanical bioscrubber for the treatment of indoor ambient air.

This study explores the effectiveness of a botanical bioscrubber system using Golden Pothos (Epipremnum aureum) in hydroponic setups to mitigate common indoor atmospheric pollutants. Over a 100-day operation, levels of SO2, NO2, O3, TVOC, CO, CO2, PM10, and PM2.5 were monitored, with a significant reduction in carbon-based compounds and particulate matter-. Notably, CO2 and PM2.5 removal efficiencies were significantly correlated with the foliar area, suggesting that the interaction between pollutants and plant leaves plays a crucial role in the phytoremediation process. In contrast, CO, PM10, and TVOC exhibited varied removal efficiencies, hinting the involvement of mechanisms beyond leaf interaction, such as adsorption in irrigation water or root system capture. The absence of significant correlations for PM10 emphasized the need for further investigation into alternative removal processes, potentially mediated by the root system. Overall, our findings suggest that botanical bioscrubbers, particularly those utilizing Golden Pothos, hold promise for indoor air purification through plant-based systems.

Growth of Leucoagaricus gongylophorus Möller (Singer) and production of key enzymes in submerged and solid-state cultures with lignocellulosic substrates.

The aim of this study was to characterize the growth of the fungus Leucoagaricus gongylophorus LEU18496, isolated from the fungus garden of the nest of leaf cutter ants Atta mexicana. The fungus garden was cultivated in an artificial laboratory nest and the fungus further grown in submerged (SmC) and solid state (SSC) cultures with sugarcane bagasse, grass or model substrates containing CM-cellulose, xylan or lignin. The CO2 production rate with grass in SmC (Vmax 34.76 mg CO2 Lgas-1 day- 1) was almost four times than SSC (Vmax 9.49 mg CO2 Lgas-1 day- 1), while the production rate obtained in sugarcane bagasse in SmC (Vmax 16.02 mg CO2 Lgas-1 day- 1) was almost three times than that for SSC (Vmax 5.42 mg CO2 Lgas-1 day- 1). In addition, the fungus grew with defined carbon substrates mixtures in SmC, but at different rates, first xylan, followed by CM-cellulose and lignin. Endoglucanase and xylanase activities (U mgprotein-1) were detected in all cultures, the specific activity was higher in the fungus-garden, 5.2 and 1.8; followed by SSC-grass, 1.5 and 0.8, and SSC-bagasse, 0.9 and 0.8, respectively. Laccase activity in the fungus-garden was 44.8 U L- 1 and 10.9 U L- 1 in the SSC-grass. The gongylidia structures observed by environmental scanning electron microscopy were ca. 40 µm and the hyphae width ca. 5 µm. The results show that L. gongylophorus from A. mexicana have promising applications for the treatment of plant residues to release fermentable sugars and the production of high value lignocellulolytic enzymes such as endoglucanase, xylanase or laccases.

A systematic comparison of two empirical gas-liquid mass transfer determination methodologies to characterize methane biodegradation in stirred tank bioreactors.

This study aimed at systematically comparing the potential of two empirical methods for the estimation of the volumetric CH4 mass transfer coefficient (klaCH4), namely gassing-out and oxygen transfer rate (OTR), to describe CH4 biodegradation in a fermenter operated with a methanotrophic consortium at 400, 600 and 800 rpm. The klaCH4 estimated from the OTR methodology accurately predicted the CH4 elimination capacity (EC) under CH4 mass transfer limiting conditions regardless of the stirring rate (∼9% of average error between empirical and estimated ECs). Thus, empirical CH4-ECs of 37.8 ±â€¯5.8, 42.5 ±â€¯5.4 and 62.3 ±â€¯5.2 g CH4 m-3 h-1vs predicted CH4-ECs of 35.6 ±â€¯2.2, 50.1 ±â€¯2.3 and 59.6 ±â€¯3.4 g CH4 m-3 h-1 were recorded at 400, 600 and 800 rpm, respectively. The rapid Co2+-catalyzed reaction of O2 with SO3-2 in the vicinity of the gas-liquid interphase during OTR determinations, mimicking microbial CH4 uptake in the biotic experiments, was central to accurately describe the klaCH4.

Ozone and hydrogen peroxide as strategies to control biomass in a trickling filter to treat methanol and hydrogen sulfide under acidic conditions.

The operation and performance of a biotrickling filter for methanol (MeOH) and hydrogen sulfide (H2S) removal at acid pH was studied. Excess biomass in the filter bed, causing performance loss and high pressure drop, was controlled by intermittent addition, of ozone (O3) and hydrogen peroxide (H2O2). The results showed that after adaptation to acid pH, the maximum elimination capacity (EC) reached for MeOH was 565 g m-3 h -1 (97 % RE). High MeOH loads resulted in increased biomass concentration within the support, triggering reductions in the removal efficiency (RE) for both compounds close to 50 %, and high pressure drop. At this stage, an inlet load of 150.2 ± 16.7 g m-3 h-1 of O3 was fed by 38 days favoring biomass detachment, and EC recovery and lower pressure dropped with a maximum elimination capacity of 587 g m-3 h-1 (81 % RE) and 15.8 g m-3 h-1 (97 % RE) for MeOH and H2S, respectively. After O3 addition, a rapid increase in biomass content and higher fluctuations in pressure drop were observed reducing the system performance. A second treatment with oxidants was implemented feeding a O3 load of 4.8 ± 0.1 g m-3 h-1 for 7 days, followed by H2O2 addition for 23 days, registering 607.5 gbiomass L-1packing before and 367.5 gbiomass L-1packing after the oxidant addition. PCR-DGGE analysis of different operating stages showed a clear change in the bacterial populations when O3 was present while the fungal population was less affected.

Modeling the effects of biomass accumulation on the performance of a biotrickling filter packed with PUF support for the alkaline biotreatment of dimethyl disulfide vapors in air.

Excess biomass buildup in biotrickling filters leads to low performance. The effect of biomass accumulation in a biotrickling filter (BTF) packed with polyurethane foam (PUF) was assessed in terms of hydrodynamics and void space availability in a system treating dimethyl disulfide (DMDS) vapors with an alkaliphilic consortium. A sample of colonized support from a BTF having been operating for over a year was analyzed, and it was found that the BTF void bed fraction was reduced to almost half of that calculated initially without biomass. Liquid flow through the examined BTF yielded dispersion coefficient values of 0.30 and 0.72 m(2) h(-1), for clean or colonized PUF, respectively. 3D images of attached biomass obtained with magnetic resonance imaging allowed to calculate the superficial area and the biofilm volume percentage and depth as 650 m(2) m(-3), 35%, and 0.6 mm respectively. A simplified geometric approximation of the complex PUF structure was proposed using an orthogonal 3D mesh that predicted 600 m(2) m(-3) for the same biomass content. With this simplified model, it is suggested that the optimum biomass content would be around 20% of bed volume. The activity of the microorganisms was evaluated by respirometry and the kinetics represented with a Haldane equation type. Experimentally determined parameters were used in a mathematical model to simulate the DMDS elimination capacity (EC), and better description was found when the removal experimental data were matched with a model including liquid axial dispersion in contrast to an ideal plug flow model.

Assessment of Culture Systems to Produce Bacterial Cellulose with a Kombucha Consortium.

Bacterial cellulose (BC) is an emerging material for high-end applications due to its biocompatibility and physicochemical characteristics. However, the scale-up production of this material is still expensive, with the culture medium constituting one-third of the total cost. Herein, four different media (yeast nitrogen base, YNB; Murashige and Skoog, MSO; black tea; and NPK fertilizer solution) were compared while using sucrose as an additional carbon source. The yields of BC were best for YNB and fertilizer with 0.37 and 0.34 gBC/gC respectively. These two were then compared using glucose as a carbon source, with improvements in the production of 29% for the fertilizer, while only an 8% increase for YNB was seen; however, as the carbon concentration increased with a fixed N concentration, the yield was lower but the rate of production of BC increased. The obtained BC films were sanitized and showed low molecular weight and all the expected cellulose characteristic FT-IR bands while SEM showed nanofibers around 0.1 µm. Compared to traditional methods for lab-scale production, the use of the fertilizer and the consortium represent benefits compared to traditional lab-scale BC culture methods such as a competitive cost (two times lower) while posing resilience and tolerance to stress conditions given that it is produced by microbial communities and not with a single strain. Additionally, the low molecular weight of the films could be of interest for certain coating formulations.

Biodegradation of DDT by stimulation of indigenous microbial populations in soil with cosubstrates.

Stimulation of native microbial populations in soil by the addition of small amounts of secondary carbon sources (cosubstrates) and its effect on the degradation and theoretical mineralization of DDT [l,l,l-trichloro-2,2-bis(p-chlorophenyl)ethane] and its main metabolites, DDD and DDE, were evaluated. Microbial activity in soil polluted with DDT, DDE and DDD was increased by the presence of phenol, hexane and toluene as cosubstrates. The consumption of DDT was increased from 23 % in a control (without cosubstrate) to 67, 59 and 56 % in the presence of phenol, hexane and toluene, respectively. DDE was completely removed in all cases, and DDD removal was enhanced from 67 % in the control to ~86 % with all substrates tested, except for acetic acid and glucose substrates. In the latter cases, DDD removal was either inhibited or unchanged from the control. The optimal amount of added cosubstrate was observed to be between 0.64 and 2.6 mg C [Formula: see text]. The CO2 produced was higher than the theoretical amount for complete cosubstrate mineralization indicating possible mineralization of DDT and its metabolites. Bacterial communities were evaluated by denaturing gradient gel electrophoresis, which indicated that native soil and the untreated control presented a low bacterial diversity. The detected bacteria were related to soil microorganisms and microorganisms with known biodegradative potential. In the presence of toluene a bacterium related to Azoarcus, a genus that includes species capable of growing at the expense of aromatic compounds such as toluene and halobenzoates under denitrifying conditions, was detected.

Morphological changes, chitinolytic enzymes and hydrophobin-like proteins as responses of Lecanicillium lecanii during growth with hydrocarbon.

Lecanicillium lecanii, Verticillium chlamydosporium, V. fungicola var flavidum and Beauveria bassiana were evaluated on their growth with pure n-hexane, toluene and n-hexane:toluene 17:83 (v:v) mixture. Another set of treatments were conducted with colloidal chitin as additional carbon source. All the strains of Lecanicillium were able to grow using hydrocarbons with or without the addition of chitin, although the presence of hydrocarbons showed significant inhibition evidenced by measured biomass, radial growth and microscopic analyses. Degradation of n-hexane ranged within 43 and 62 % and it was higher than that with toluene. The strains L460, L157 and L2149, which presented the highest growth, were further selected for determinations of hydrocarbon consumptions in microcosms. Strain L157 showed the highest consumption of n-hexane (55.6 %) and toluene (52.9 %) as sole carbon source and it also displayed activities of endochitinases, N-acetylhexosaminidase and production of hydrophobins class I and II.

Characterization of artificially dried biofilms for air biofiltration studies.

One of the main problems associated with the operation of air biofilters is the loss of performance caused by drying of the bioactive support, as the removal capacity of contaminants by the microorganisms is dependent on their water content. In this work, biofilms from a microbial consortium adapted to toluene were grown on stainless steel slides. The biofilms were dried in stoppered flasks with saturated saline solutions to obtain final water activities of 97.4 %, 83.9 %, 74.8 % and 32 %. The biofilms were characterized by a sorption isotherm Type III with toluene; the water desorption isotherm was fitted to the BET model and the biofilm hydrophobicity was also determined. Specific oxygen consumption rates decreased at lower Aw from 60 µg O(2)/mg protein/h to zero activity. Biofilm activity, represented by a toluene consumption rate, and others physical properties presented a critical point between Aw 0.84 and 0.97. Biological activity of dried biofilms was restored either partially or completely, depending on the extent of drying and rewetting method.

Biodegradation of methyl tert-butyl ether by cometabolism with hexane in biofilters inoculated with Pseudomonas aeruginosa.

Biodegradation of methyl tert-butyl ether (MTBE) vapors by cometabolism with gaseous hexane (n-hexane > 95%) was investigated using Pseudomonas aeruginosa utilizing short chain aliphatic hydrocarbon (C(5)-C(8)). Kinetic batch experiments showed that MTBE was degraded even when hexane was completely exhausted with a cometabolic coefficient of 1.06 ± 0.16 mg MTBE mg hexane(-1). Intermediate tert-butyl alcohol (TBA) accumulation was observed followed by its gradual consumption. A maximum MTBE elimination capacity (EC(MAX)) of 35 g m(-3) h(-1) and removal efficiency (RE) of 70% were attained in mineral medium amended biofilters having an empty bed residence time (EBRT) of 1 min. For these experimental conditions, a maximum hexane EC of approximately 60 g m(-3) h(-1) was obtained at a load of 75 g m(-3) h(-1). Experiments under transient conditions revealed a competitive substrate interaction between MTBE and hexane. Biomass densities between 5.8 and 12.6 g L(biofilter) (-1) were obtained. Nevertheless, production of biopolymers caused non-uniform distribution flow rates that reduced the performance. Residence time distribution profiles showed an intermediate dispersion flow rate with a dispersion coefficient of 0.8 cm(2) s(-1).

Temperature and moisture effect on spore emission in the fungal biofiltration of hydrophobic VOCs.

The effect of temperature and moisture on the elimination capacity (EC), CO(2) production and spore emission by Fusarium solani was studied in biofilters packed with vermiculite and fed with n- pentane. Three temperatures (15, 25 and 35°C) were tested and the highest average EC (64 g m(-3) h(-1)) and lower emission of spores (2.0 × 10(3) CFU m(-3) air) were obtained at 25°C. The effect of moisture content of the packing material indicates that the highest EC (65 g m(-3) h(-1)) was obtained at 50 % moisture. However, lowest emission (1.3 × 10(3) CFU m(-3) air) was obtained at 80 % moisture. Furthermore, the results show that a slight decrease in spore emission was found with increasing moisture content. In all cases, the depletion of the nitrogen source in the biofilter induced the sporulation, a decay of the EC and increased spore emission.

Elimination of hydrophobic volatile organic compounds in fungal biofilters: reducing start-up time using different carbon sources.

Fungal biofilters have been recently studied as an alternative to the bacterial systems for the elimination of hydrophobic volatile organic compounds (VOC). Fungi foster reduced transport limitation of hydrophobic VOCs due to their hydrophobic surface and extended gas exchange area associated to the hyphal growth. Nevertheless, one of their principal drawbacks is their slow growth, which is critical in the start-up of fungal biofilters. This work compares the use of different carbon sources (glycerol, 1-hexanol, wheat bran, and n-hexane) to reduce the start-up period and sustain high n-hexane elimination capacities (EC) in biofilters inoculated with Fusarium solani. Four parallel experiments were performed with the different media and the EC, the n-hexane partition coefficient, the biomass production and the specific consumption rate were evaluated. Biofilters were operated with a residence time of 1.3 min and an inlet n-hexane load of 325 g m(-3) (reactor) h(-1). The time to attain maximum EC once gaseous n-hexane was fed was reduced in the three experiments with alternate substrates, as compared to the 36 days needed with the control where only n-hexane was added. The shortest adaptation period was 7 days when wheat bran was initially used obtaining a maximum EC of 160 g m(-3) (reactor) h(-1) and a critical load of 55 g m(-3) (reactor) h(-1). The results were also consistent with the pressure drop, the amount of biomass produced and its affinity for the gaseous n-hexane, as represented by its partition coefficient.

Operational parameters in H2S biofiltration under extreme acid conditions: performance, biomass control, and CO2 consumption.

This paper reports the treatment of gaseous hydrogen sulfide, H2S, in a biotrickling filter (BTF) under extreme acidic pH conditions (≈ 1.2). The effect of adding thiosulfate (Na2S2O3.5H2O) to promote biomass growth, feeding low concentrations of ozone to control excess biomass, and the carbon dioxide, CO2, consumption by the chemolithoautotrophic consortium were evaluated. The results showed a global removal efficiency over 98.0% with loads of H2S > 50 g m-3 h-1 (at 639 ppmv) and a linear relation between H2S elimination capacity with the CO2 consumption rate of around 0.1 gCO2/gH2S. Supplementing sulfur in the medium with 2 g L-1 thiosulfate resulted in negative effect performance. Respirometry tests proved that the consortium could not utilize this sulfur form at this pH. Additionally, continuous and intermittent O3 feeding to the BTF in gaseous concentrations of 98 ± 5.4 mg m-3 caused a slight decreased in the performance but the biomass activity in the BTF was only slightly affected allowing a quick performance recovery once O3 addition was suspended.

Methanotroph-microalgae co-culture for greenhouse gas mitigation: Effect of initial biomass ratio and methane concentration.

This work evaluated the effect of different initial biomass ratios in a co-culture of an alkaliphilic methanotrophic bacteria consortium (AMB) and the green microalga Scenedesmus obtusiusculus (GM) on the maximum CH4 specific biodegradation rate and global carbon uptake. The highest maximum specific biodegradation rate was 589 ± 0.01 mgCH4 gbiomass-1 d-1 obtained for a proportion of 3:1 AMB-GM (w w-1) and 8% of initial CH4 in the headspace. The methane degradation rate was 1.5 times lower than the value obtained solely by the AMB consortium, and it was associated with pH increases due to the evolved CO2 consumption by the microalga. Increased activity of the AMB consortium along the experiments was due to progressive adaptation. Massive sequencing revealed the presence of methanotrophic/methylotrophic species such as Methylocystis sp., Methylomicrobium sp., Methylophaga sp., and Hyphomicrobium sp. Successful complete methane and carbon dioxide uptake was obtained with the 3:1, 4:1, and 5:1 AMB-GM biomass ratios, while for the rest of the ratios tested, more than 70% of the initial methane was transformed into biomass and inorganic carbon. This study showed that methanotrophic-microalgal co-cultures lead to a promising strategy for greenhouse gases mitigation in one step.

Hydrophobic response of the fungus Rhinocladiella similis in the biofiltration with volatile organic compounds with different polarity.

Rhinocladiella similis biodegraded volatile organic compounds (VOCs) of different polarity in gas-phase biofilters. Elimination capacities, (EC) of 74 g(hexane) m(-3) h(-1), 230 g(ethanol) m(-3) h(-1), 85 g(toluene) m(-3) h(-1) and 30 g(phenol) m(-3) h(-1) were obtained. EC values correlated with the solubility of the VOCs. R. similis grown with n-hexane or ethanol in biofilters packed with Perlite showed that the surface hydrophobicity was higher with n-hexane than ethanol. The hydrophobin-like proteins extracted from the mycelium produced with n-hexane (15 kDa) were different from those in the ethanol biofilter (8.5 kDa and 7 kDa).

Mineralization of methyl tert-butyl ether and other gasoline oxygenates by Pseudomonads using short n-alkanes as growth source.

Biodegradation of methyl tert-butyl ether (MTBE) by cometabolism has shown to produce recalcitrant metabolic intermediates that often accumulate. In this work, a consortium containing Pseudomonads was studied for its ability to fully degrade oxygenates by cometabolism. This consortium mineralized MTBE and TBA with C3-C7 n-alkanes. The highest degradation rates for MTBE (75 +/- 5 mg g(protein) (-1) h(-1)) and TBA (86.9 +/- 7.3 mg g(protein) (-1) h(-1)) were obtained with n-pentane and n-propane, respectively. When incubated with radiolabeled MTBE and n-pentane, it converted more than 96% of the added MTBE to (14)C-CO(2). Furthermore, the consortium degraded tert-amyl methyl ether, tert-butyl alcohol (TBA), tert-amyl alcohol, ethyl tert-butyl ether (ETBE) when n-pentane was used as growth source. Three Pseudomonads were isolated but only two showed independent MTBE degradation activity. The maximum degradation rates were 101 and 182 mg g(protein) (-1) h(-1) for Pseudomonas aeruginosa and Pseudomonas citronellolis, respectively. The highest specific affinity (a degrees (MTBE)) value of 4.39 l g(protein) (-1) h(-1) was obtained for Pseudomonas aeruginosa and complete mineralization was attained with a MTBE: n-pentane ratio (w/w) of 0.7. This is the first time that Pseudomonads have been reported to fully mineralize MTBE by cometabolic degradation.

Estimating CO2 and VOCs production of Colletotrichum fragariae and Rhizopus stolonifer grown in cold stored strawberry fruit.

The aim of this work was to investigate the early detection of anthracnose and soft rot diseases in cold stored strawberry fruit by evaluating the CO2 and volatile organic compounds (VOCs) released by the fungi Colletotrichum fragariae and Rhizopus stolonifer. Strawberries were stored at 5, 10 and 21 °C (control group) and the VOCs and CO2 production of inoculated and non-inoculated strawberries were followed by gas chromatography. To evaluate and estimate the growth of both fungi, the CO2 data were fitted to the Gompertz model. Data of the VOCs released at the end of the fungal growth were analyzed using principal components analysis (PCA) to discriminate between infected and non-infected strawberries. The results showed that fungal growth was affected by temperature and C. fragariae had a maximum growth after 14.6 h at 5 °C and R. stolonifer at 21 °C after 45.2 h. On the other hand, through VOCs released by C. fragariae and R. stolonifer and PCA, four groups were obtained: a) strawberry infected with C. fragariae, stored at 10 °C, b) strawberry infected with R. stolonifer, stored at 21 °C, c) control group kept at 10 °C and, d) strawberry infected with C. fragariae and control group (5 and 21 °C), and strawberry infected with R. stolonifer at 5 and 10 °C. In conclusion, CO2 and VOCs released by C. fragariae and R. stolonifer on strawberries could infer the presence of anthracnose and soft rot during storage of the fruit at low temperature.

Biological treatment of indoor air for VOC removal: potential and challenges.

There is nowadays no single fully satisfactory method for VOC removal from indoor air due to the difficulties linked to the very low concentration (microg m(-3) range), diversity, and variability at which VOCs are typically found in the indoor environment. Although biological methods have shown a certain potential for this purpose, the specific characteristic of indoor air and the indoor air environment brings numerous challenges. In particular, new methods must be developed to inoculate, express, and maintain a suitable and diverse catabolic ability under conditions of trace substrate concentration which might not sustain microbial growth. In addition, the biological treatment of indoor air must be able to purify large amounts of air in confined environments with minimal nuisances and release of microorganisms. This requires technical innovations, the development of specific testing protocols and a deep understanding of microbial activities and the mechanisms of substrate uptake at trace concentrations.

Phenomenological model of fungal biofilters for the abatement of hydrophobic VOCs.

This work describes the growth of filamentous fungi in biofilters for the degradation of hydrophobic VOCs. The study system was n-hexane and Fusarium solani B1. The system is mathematically described and the main physical, kinetic data and morphological parameters were obtained by independent experiments and validated with data from laboratory experiments. The model describes the increase in the transport area by the growth of the filamentous cylindrical mycelia and its relation with n-hexane elimination in quasi-stationary state in a biofilter. The model describing fungal growth includes Monod-Haldane kinetic and hyphal elongation and ramification. A specific surface area of transport (SSAT) of 1.91 x 10(5) m(2) m(-3) and a maximum elimination capacity (EC) of 248 g m(-3) h(-1) were obtained by the mathematical model simulation, with a 10% of error with respect to the experimental EC.