Temperature versus Relative Humidity: Which Is More Important for Indoor Mold Prevention?

Temperature is known as one of the abiotic factors that can affect mold growth. Many mold growth prediction models consider temperature as one of the parameters that can significantly impact mold growth indoors, and hence temperature has been targeted by different indoor mold prevention strategies on different premises. For example, European guidelines for libraries suggest a temperature of 19 °C to preserve books. However, running low temperature air-conditioning (AC) costs substantially more energy, and thus a higher temperature (e.g., 25.5 °C) has been regularly proposed as the recommended indoor temperature for general indoor environments in Hong Kong. It is, therefore, needed to understand whether or not the reduction of indoor temperature would lead to better effectiveness of mold prevention. Using Cladosporium cladosporioides (C. cladosporioides) as the model, its germinating spores were challenged in C. cladosporioides to wet-dry cycles with different combinations of relative humidity (RH, 40%, 60% and 80%) and temperature (19 °C and 28 °C) levels. The survival, lipid peroxidation and catalase (CAT) activity of the treated spores were monitored and compared. C. cladosporioides spores showed similar levels of viability, lipid peroxidation and CAT activity when they were exposed to 19 °C and 28 °C at the same RH, but substantially lower survival and higher oxidative stress were observed under the wet-dry cycles with 40% RH dry periods compared with 60% and 80% RH at both temperatures, suggesting that indoor temperature does not tend to affect the resistance of C. cladosporioides to wet-dry cycles as significantly as the RH level of the dry period. Collectively, this study suggests a more important role for moisture over temperature in indoor mold prevention. The outcome of this study may facilitate the sustainable management of indoor mold problems in buildings.

Self-cleaning MnZn ferrite/biochar adsorbents for effective removal of tetracycline.

A renewable tri-metallic spinel decorated biochar adsorbent (MZF-BC) was fabricated by a facile hydrothermal method and to remove tetracycline. The physicochemical properties of MZF-BC were well studied. MZF-BC with a hybrid pore structure of mesopores (~7.6 nm) and macropores (~50 nm) has the maximum tetracycline adsorption capacity reaching 142.4 mg g-1. Through the study of adsorption kinetics, isotherms and key influencing factors, it was found that MZF-BC adsorption on tetracycline was primarily multi-layer effect with the initial adsorption behavior of pore filling associated with hydrogen bonding and π-π stacking. Furthermore, the MZF-BC performs excellent regeneration ability by driving Fenton-like catalysis as the self-cleaning process in the liquid phase. This study contributes to a new insight into the in-situ regeneration of biochar-based adsorbents after adsorbing organic pollutants in pharmaceutical wastewater treatment.

Mechanisms of indoor mold survival under moisture dynamics, a special water treatment approach within the indoor context.

Mold contamination is one of the most important causes for indoor air pollution. Previous studies have indicated the feasibility of employing wet-dry cycles, a special water treatment approach in indoor environments, to control indoor mold contamination. However, the underlying mechanisms regulating the responses of indoor molds to changing moisture conditions remains to be elucidated. Here, we studied the mechanisms regulating the responses to wet-dry cycles (termed as moisture dynamics) in Aspergillus penicillioides, Cladosporium cladosporioides, and Aspergillus niger. First, the dormant spores of each mold species were grown to the swollen stage. Next, swollen spores were incubated at different water activity (aw) levels (0.4, 0.6 and 0.8 aw) for up to 15 days. Afterward, the viability, lipid peroxidation and antioxidant activities (both enzymatic and non-enzymatic) of treated molds were determined. Our results show that the mold species that survived better under moisture dynamics also encountered less oxidative damage and exhibited stronger antioxidant activities. Moreover, lower RH imposed severer oxidative stress to C. cladosporioides and A. niger. Pearson correlation coefficient indicate significant correlations between oxidative stress and aw of dry periods, oxidative damage and mold survival, as well as oxidative responses and mold survival. Collectively, these results imply that oxidative stress adaptation regulates the viability of A. penicillioides, C. cladosporioides, and A. niger in response to moisture dynamics. Our findings facilitate the development of novel engineering solutions for indoor air pollution.

A Review of the Use of Carbon Nanotubes and Graphene-Based Sensors for the Detection of Aflatoxin M1 Compounds in Milk.

This paper presents a comprehensive review of the detection of aflatoxin compounds using carbon allotrope-based sensors. Although aflatoxin M1 and its derivative aflatoxin B1 compounds have been primarily found in milk and other food products, their presence above a threshold concentration causes disastrous health-related anomalies in human beings, such as growth impairment, underweight and even carcinogenic and immunosuppressive effects. Among the many sensors developed to detect the presence of these compounds, the employment of certain carbon allotropes, such as carbon nanotubes (CNTs) and graphene, has been highly preferred due to their enhanced electromechanical properties. These conductive nanomaterials have shown excellent quantitative performance in terms of sensitivity and selectivity for the chosen aflatoxin compounds. This paper elucidates some of the significant examples of the CNTs and graphene-based sensors measuring Aflatoxin M1 (ATM1) and Aflatoxin B1 (AFB1) compounds at low concentrations. The fabrication technique and performance of each of the sensors are shown here, as well as some of the challenges existing with the current sensors.

On-site CO2 bio-sequestration in anaerobic digestion: Current status and prospects.

The advantages of anaerobic digestion (AD) technology in organic solid waste treatment for bioenergy recovery are evidenced in worldwide. Recently, more attention has been paid to on-site biogas research, as well as biogenic CO2 sequestration from AD plant, to promote "carbon neutral". Single-phase and two-phase AD system can be incorporated with various CO2 bioconversion technologies through H2 mediated CO2 bioconversion (in-situ and ex-situ biogas upgrading), or other emerging strategies for CO2 fixation without exogenous H2 injection; these include in-situ direct interspecies electron transfer reinforcement, electromethanogenesis, and off-gas reutilization. The existing and potential scenarios for on-site CO2 bio-sequestration within the AD framework are reviewed from the perspectives of metabolic pathways, functional microorganisms, the limitations on reaction kinetics. This review concluded that on-site CO2 bio-sequestration is a promising solution to reduce greenhouse gas emissions and increase renewable energy recovery.

Assessing the stability of co-digesting sewage sludge with pig manure under different mixing ratios.

This study assessed the digester stability and overall methane production of co-digestion of sewage sludge (SS) and pig manure (PM). Four different ratios of PM were mixed with SS to reach different final concentrations of total solids (TS), i.e. 4%, 6%, 8% and 10%. Volatile solids (VS) reduction rate decreased along with an increase in TS%, and the maximum cumulative methane yield of 342 mL/g VSrem was obtained in treatment with TS of 6%. When TS was ≥ 8%, accumulation of volatile fatty acids (VFAs), free ammonium nitrogen (FAN) and total ammonium nitrogen (TAN) were observed. At a TS content of 10%, VFAs accumulated to > 20000 mg/L and the highest FAN was 481 mg/L. The suppression of methanogenesis was negatively correlated with FAN and VFA/TIC (P < 0.05). Co-digestion demonstrated to be an effective way to improve the methane yield from SS due to the enriched biodegradable organic substance and more balanced C/N ratio by incorporating PM.

Impact of pyrochar and hydrochar derived from digestate on the co-digestion of sewage sludge and swine manure.

Four kinds of biochar were obtained by pyrolysis carbonization and hydrothermal carbonization from swine manure digestate, i.e. pyrochar (HC, HC-Fe) and hydrochar (HTC, HTC-Fe). Batch fermentation was conducted to compare their effects on the co-digestion of sewage sludge and swine manure. Both pyrochar and hydrochar present positive effect on methane production, nevertheless the higher methane yields were obtained in HTC and HTC-Fe digesters. No advantage was observed for the iron impregnation. The maximum methane yield was 308.4 mL/g VS in HTC digester, which was 27% and 49% higher than HC and Control, respectively. The surface functional groups of hydrochar are more abundant than pyrochar, which is favorable for promoting the syntrophic anaerobic metabolism, as revealed by the promoted substrate hydrolysis and VFAs consumption rate. Thus, it is proposed to convert swine manure digestate to hydrochar, which can be recirculated back to the AD reactor to increase the digestion efficiency.

The role of oxidative stress in the growth of the indoor mold Cladosporium cladosporioides under water dynamics.

Moisture is one of the critical abiotic factors that can affect mold growth. Indoor humidity is typically fluctuating, which renders a transient water supply for mold growth. Understanding mold growth under water dynamics and its underlying mechanisms can help in the development of novel and sustainable mold prevention strategies. In this study, pre-germination and germinated spores of Cladosporium cladosporioides were exposed to daily wet-dry cycles with different combinations of wetting and drying duration. Afterward, growth delay, cellular H2 O2 concentration, and catalase (CAT) activity were measured and compared. We found that under daily wet-dry cycles, the longer the growth delay was observed, the higher the cellular H2 O2 concentration was detected, with the 12-12 wet-dry cycle (12-hour wet and 12-hour dry) showing the longest growth delay and highest cellular H2 O2 production. A positive correlation between cellular H2 O2 concentration and growth delay was suggested by Pearson correlation coefficient and linear regression analysis (P < .0001, R2  = 0.85). Furthermore, under daily wet-dry cycles, molds derived from pre-germination spores generally exhibited shorter growth delay, lower cellular H2 O2 concentration, and higher CAT activity than molds developed from germinated spores. These results together suggest that the growth delay of C. cladosporioides under water dynamics is associated with oxidative stress.

Crucifera sulforaphane (SFN) inhibits the growth of nasopharyngeal carcinoma through DNA methyltransferase 1 (DNMT1)/Wnt inhibitory factor 1 (WIF1) axis.

BACKGROUND: Sulforaphane (SFN), a natural compound present in cruciferous vegetable, has been shown to possess anti-cancer activities. Cancer stem cell (CSC) in bulk tumor is generally considered as treatment resistant cell and involved in cancer recurrence. The effects of SFN on nasopharyngeal carcinoma (NPC) CSCs have not yet been explored. PURPOSE: The present study aims to examine the anti-tumor activities of SFN on NPC cells with CSC-like properties and the underlying mechanisms. METHODS: NPC cells growing in monolayer culture, CSCs-enriched NPC tumor spheres, and also the NPC nude mice xenograft were used to study the anti-tumor activities of SFN on NPC. The population of cells expressing CSC-associated markers was evaluated using flow cytometry and aldehyde dehydrogenase (ALDH) activity assay. The effect of DNA methyltransferase 1 (DNMT1) on the growth of NPC cells was analyzed by using small interfering RNA (siRNA)-mediated silencing method. RESULTS: SFN was found to inhibit the formation of CSC-enriched NPC tumor spheres and reduce the population of cells with CSC-associated properties (SRY (Sex determining Region Y)-box 2 (SOX2) and ALDH). In the functional study, SFN was found to restore the expression of Wnt inhibitory factor 1 (WIF1) and the effect was accompanied with the downregulation of DNMT1. The functional activities of WIF1 and DNMT1 were confirmed using exogenously added recombinant WIF1 and siRNA knockdown of DNMT1. Moreover, SFN was found to inhibit the in vivo growth of C666-1 cells and enhance the anti-tumor effects of cisplatin. CONCLUSION: Taken together, we demonstrated that SFN could suppress the growth of NPC cells via the DNMT1/WIF1 axis.

Evaluation of integrated ammonia recovery technology and nutrient status with an in-vessel composting process for swine manure.

The study investigated the effect of different initial moisture (IM) content (55, 60, 65, and 70%) of composting mixtures (swine manure and sawdust) for the production of nutrient rich manure, and the recovery of ammonia through a condensation process using a vertical cylindrical in-vessel composter for 56days. The composting resulted in a significant reduction in C:N ratio and electrical conductivity (EC), with a slight increase in pH in all products. The NH3 were emitted notably, and at the same time the NO3--N concentration gradually increased with the reduction of NH4+-N in the composting mixtures. The overall results confirmed, the 65% IM showed the maximum nutritional yield, maturity and non-phytotoxic effects (Lycopersicon esculentum L.), with the results of ideal compost product in the following order of IM: 65%>60%>70%>55%. Finally, the recovered condensed ammonia contained considerable ammonium nitrogen concentrations and could be used as fertilizer.

Evaluation of pilot-scale in-vessel composting for Hanwoo manure management.

The study investigated the effect of in-vessel composting process on Hanwoo manure in two different South Korea regions (Pyeongchang and Goechang) with sawdust using vertical cylindrical in-vessel bioreactor for 42days. The stability and quality of Hanwoo manure in both regions were improved and confirmed through the positive changes in physico-chemical and phytotoxic properties using different commercial seed crops. The pH and electrical conductivity (EC, ds/m) of composted manure in both regions were slightly increased. At the same time, carbon:nitrogen (C:N) ratio and ammonium nitrogen:nitrate nitrogen (NH4+-N:NO3--N) ratio decreased to 13.4-16.1 and 0.36-0.37, respectively. The germination index (GI, %) index was recorded in the range of 67.6-120.9%, which was greater than 50%, indicating phytotoxin-free compost. Although, composted manure values in Goechang region were better in significant parameters, overall results confirmed that the composting process could lead to complete maturation of the composted product in both regions.

Application of recombinant Pediococcus acidilactici BD16 (fcs +/ech +) for bioconversion of agrowaste to vanillin.

Biotechnological production of vanillin is gaining momentum as the natural synthesis of vanillin that is very expensive. Ferulic acid (FA), a costly compound, is used as the substrate to produce vanillin biotechnologically and the making process is still expensive. Therefore, this study investigated the practical use of an agrobiomass waste, rice bran, and provides the first evidence of a cost-effective production of vanillin within 24 h of incubation using recombinant Pediococcus acidilactici BD16 (fcs +/ech +). Introduction of two genes encoding feruloyl CoA synthetase and enoyl CoA hydratase into the native strain increased vanillin yield to 4.01 g L-1. Bioconversion was monitored through the transformation of phenolic compounds. A hypothetical metabolic pathway of rice bran during the vanillin bioconversion was proposed with the inserted pathway from ferulic acid to vanillin and compared with that of other metabolic engineered strains. These results could be a gateway of using recombinant lactic acid bacteria for industrial production of vanillin from agricultural waste.

Effect of composites based nickel foam anode in microbial fuel cell using Acetobacter aceti and Gluconobacter roseus as a biocatalysts.

This study explores the use of materials such as chitosan (chit), polyaniline (PANI) and titanium carbide (TC) as anode materials for microbial fuel cells. Nickel foam (NF) was used as the base anode substrate. Four different types of anodes (NF, NF/PANI, NF/PANI/TC, NF/PANI/TC/Chit) are thus prepared and used in batch type microbial fuel cells operated with a mixed consortium of Acetobacter aceti and Gluconobacter roseus as the biocatalysts and bad wine as a feedstock. A maximum power density of 18.8Wm(-3) (≈2.3 times higher than NF) was obtained in the case of the anode modified with a composite of PANI/TC/Chit. The MFCs running under a constant external resistance of (50Ω) yielded 14.7% coulombic efficiency with a maximum chemical oxygen demand (COD) removal of 87-93%. The overall results suggest that the catalytic materials embedded in the chitosan matrix show the best performance and have potentials for further development.

Influence of ionic conductivity in bioelectricity production from saline domestic sewage sludge in microbial fuel cells.

This study aimed at manipulating ionic conductivity (EC) to harvest the maximum electrical energy from seawater-based domestic wastewater sewage sludge (SWS), unique to only a few cities, through microbial fuel cell (MFC). SWS has never been investigated as a MFC substrate before, and thus the influence of high in-situ EC on the energy recovery was unknown. In this study, the EC of the SWS was reduced through mixing it with fresh water-based domestic wastewater sewage sludge (FWS) or diluted 50% using deionized water while FWS and SWS were individually served as reference treatments. SWS:FWS mix (1:1) exhibited a maximum Coulombic efficiency of 28.6±0.5% at a COD removal of 59±3% while the peak power density was 20-fold higher than FWS. The improved performance was due to the lower ohmic internal resistance (36.8±4.2Ω) and optimal conductivity (12.8±0.2mScm(-1)). Therefore, dilution with FWS could enhance energy recovery from SWS.

Preliminary occurrence studies of antibiotic residues in Hong Kong and Pearl River Delta.

An improved liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to investigate the occurrence of selected antibiotic residues in Hong Kong and Pearl River Delta. LC and MS parameters were optimized to produce the maximum analytical responses for each compound. The established method targeted five groups of antibiotics, namely, macrolides, sulfonamides, tetracyclines, quinolones, and amphenicols. The method was validated for three types of environmental water matrices, namely, reservoir, river, and estuarine waters. Low detection limits of 0.17-0.18 ng/L for macrolides, 0.22-0.34 ng/L for quinolones, 0.67-1.65 ng/L for tetracyclines, and 0.27-0.56 ng/L for sulfonamides were obtained. No apparent interferences were observed in the chromatograms of all antibiotics groups. The developed method was preliminarily used to analyze water samples collected from Yuen Long River in New Territories, Hong Kong and four sites along the Pearl River Delta. Results showed that high level of tetracycline was found among the groups tested in the local river samples. In Pearl River Delta, we identified significant levels of erythromycin, roxithromycin, and sulfadiazine in Shenzhen Reservoir.

Synergistic effect of thermophilic temperature and biosurfactant produced by Acinetobacter calcoaceticus BU03 on the biodegradation of phenanthrene in bioslurry system.

This study aimed at investigating the synergistic effect of temperature and biosurfactant on the biodegradation of phenanthrene in bioslurry. Bench-scale bioslurry experiments were conducted at 25 and 55°C. The desorption rate coefficients of phenanthrene (K(des)) obtained using the pseudo-first order model were 0.0026 and 0.0035 kg mg(-1)h(-1) at 25 and 55°C, respectively. Addition of 1500 mg L(-1) biosurfactant, produced by Acinetobacter calcoaceticus BU03, marginally increased the K(des) at 25°C since most of biosurfactant was sorbed onto soil; however, significantly increased the K(des) to 0.0087 kg mg(-1)h(-1) at 55°C as the thermophilic temperature reduced the adsorption of the biosurfactant onto soil and subsequently enhanced the desorption of phenanthrene. The biodegradation of phenanthrene well fitted pseudo-first order kinetics based on the assumption that biodegradation was limited by the desorption. About 78.7% of phenanthrene was degraded in 30 days at 25°C; and addition of biosurfactant did not affect the biodegradation. However, addition of the biosurfactant or inoculation of A. calcoaceticus BU03 at 55°C significantly enhanced the biodegradation by increasing the K(des). Results indicate that synergistic application of thermophilic temperature and biosurfactant or inoculation of biosurfactant producing microorganisms is an effective and innovative method to enhance the efficiency of PAH degradation in bioslurry system.

Effects of rhamnolipids on cell surface hydrophobicity of PAH degrading bacteria and the biodegradation of phenanthrene.

The effects of rhamnolipids produced by Pseudomonas aeruginosa ATCC9027 on the cell surface hydrophobicity (CSH) and the biodegradation of phenanthrene by two thermophilic bacteria, Bacillus subtilis BUM and P. aeruginosa P-CG3, and mixed inoculation of these two strains were investigated. Rhamnolipids significantly reduced the CSH of the hydrophobic BUM and resulted in a noticeable lag period in the biodegradation. However, they significantly increased the CSH and enhanced the biodegradation for the hydrophilic P-CG3. In the absence of rhamnolipids, a mixed inoculation of BUM and P-CG3 removed 82.2% of phenanthrene within 30 days and the major contributor of the biodegradation was BUM (rapid degrader) while the growth of P-CG3 (slow degrader) was suppressed. Addition of rhamnolipids promoted the surfactant-mediated-uptake of phenanthrene by P-CG3 but inhibited the uptake through direct contact by BUM. This resulted in the domination of P-CG3 during the initial stage of biodegradation and enhanced the biodegradation to 92.7%.

Cadmium uptake potential of Brassica napus cocropped with Brassica parachinensis and Zea mays.

Cadmium uptake potential of Brassica napus co-cropped with B. parachinensis or Zea mays plants in split pot (allow the solutes to pass but prevent the interaction of roots between compartments) experiments was evaluated. Plants were grown in split pots filled with soil spiked at 0, 3, 6, 12, 25 and 50 mg Cd/kg soil. Biomass and Cd uptake were determined after 6 weeks, and rhizospheric soil solutions, extracted using soil probes, were analyzed for pH and water soluble Cd at weekly intervals. Cadmium treatments affected the biomass. Cadmium concentration in the shoots of B. napus was higher when co-cropped with B. parachinensis and significantly higher with Z. mays; however, the biomass was negatively affected implying the higher nutrient apportionment to the crop plants than B. napus. Concentration of Cd in B. napus was higher in shoots than in roots as revealed by shoot/root Cd quotient and was always >1; the quotient for B. parachinensis was approximately 1 and that of Z. mays was <1, indicating the potential of Brassicaceae members to translocate the Cd to aboveground tissue. Results indicate the feasibility of co-cropping method to clean the Cd contaminated soils.