Xinlei Wang

Qualitative and quantitative analysis on aroma characteristics of ginseng at different ages using E-nose and GC-MS combined with chemometrics

Aroma profiles of ginseng samples at different ages were investigated using electronic nose (E-nose) and GC-MS techniques combined with chemometrics analysis. The bioactive ginsenoside and volatile oil content increased with age. E-nose performed well in the qualitative analyses. Both Principal Component Analysis (PCA) and Discriminant Functions Analysis (DFA) performed well when used to analyze ginseng samples, with the first two principal components (PCs) explaining 85.51% and the first two factors explaining 95.51% of the variations. Hierarchical Cluster Analysis (HCA) successfully clustered the different types of ginsengs into four groups. A total of 91 volatile constituents were identified. 50 of them were calculated and compared using GC-MS. The main fragrance ingredients were terpenes and alcohols, followed by aromatics and ester. The changes in terpenes, alcohols, aromatics, esters, and acids during the growth year once again confirmed the dominant role of terpenes. The Partial Least Squares (PLS) loading plot of gas sensors and aroma ingredients indicated that particular sensors were closely related to terpenes. The scores plot indicated that terpenes and its corresponding sensors contributed the most in grouping. As regards to quantitative analyze, 7 constituent of terpenes could be accurately explained and predicted by using gas sensors in PLS models. In predicting ginseng age using Back Propagation-Artificial Neural Networks (BP-ANN), E-nose data was found to predict more accurately than GC-MS data. E-nose measurement may be a potential method for determining ginseng age. The combination of GC-MS can help explain the hidden correlation between sensors and fragrance ingredients from two different viewpoints.

Monitoring airborne biotic contaminants in the indoor environment of pig and poultry confinement buildings

Given the growing concerns over human and animal health issues related to confined animal feeding operations, an in-depth examination is required to monitor for airborne bacteria and associated antibiotic resistance genes. Our 16S rRNA-based pyrosequencing revealed that the airborne microbial community skewed towards a higher abundance of Firmicutes (> 59.2%) and Bacteroidetes (4.2-31.4%) within the confinement buildings, while the office environment was predominated by Proteobacteria (55.2%). Furthermore, bioaerosols in the confinement buildings were sporadically associated with genera of potential pathogens, and these genera were more frequently observed in the bioaerosols of pig and layer hen confinement than the turkey confinement buildings and office environment. High abundances of tetracycline resistance genes (9.55 × 10(2) to 1.69 × 10(6) copies ng(-1) DNA) were also detected in the bioaerosols sampled from confinement buildings. Bacterial lineages present in the poultry bioaerosols clustered apart from those present in the pig bioaerosols and among the different phases of pig production, suggesting that different livestock as well as production phase were associated with a distinct airborne microbial community. By understanding the diversity of biotic contaminants associated with the different confinement buildings, this study facilitates the implementation of better management strategies to minimize potential health impacts on both livestock and humans working in this environment.

Dynamic profiling of double-stranded RNA binding proteins

Double-stranded (ds) RNA is a key player in numerous biological activities in cells, including RNA interference, anti-viral immunity and mRNA transport. The class of proteins responsible for recognizing dsRNA is termed double-stranded RNA binding proteins (dsRBP). However, little is known about the molecular mechanisms underlying the interaction between dsRBPs and dsRNA. Here we examined four human dsRBPs, ADAD2, TRBP, Staufen 1 and ADAR1 on six dsRNA substrates that vary in length and secondary structure. We combined single molecule pull-down (SiMPull), single molecule protein-induced fluorescence enhancement (smPIFE) and molecular dynamics (MD) simulations to investigate the dsRNA-dsRBP interactions. Our results demonstrate that despite the highly conserved dsRNA binding domains, the dsRBPs exhibit diverse substrate specificities and dynamic properties when in contact with different RNA substrates. While TRBP and ADAR1 have a preference for binding simple duplex RNA, ADAD2 and Staufen1 display higher affinity to highly structured RNA substrates. Upon interaction with RNA substrates, TRBP and Staufen1 exhibit dynamic sliding whereas two deaminases ADAR1 and ADAD2 mostly remain immobile when bound. MD simulations provide a detailed atomic interaction map that is largely consistent with the affinity differences observed experimentally. Collectively, our study highlights the diverse nature of substrate specificity and mobility exhibited by dsRBPs that may be critical for their cellular function.

Strong influence of medium pH condition on gas-phase biofilter ammonia removal, nitrous oxide generation and microbial communities

Effects of pH on gas-phase biofilter performance including NH3 removal efficiency (RE), N2O generation, and microbial communities of ammonia oxidizers and denitrifies, are examined. A two-step experiment was carried out on four biofilters for 130 days. In step 1 with pH 8.0, NH3 REs were 85-95% and N2O concentrations were 0.1-0.4 ppm. In step 2, pH was adjusted to 4.5, 6.0, 8.0, and 9.5 in four biofilters, respectively. The acidified biofilters showed higher NH3 REs than the alkalized biofilters. N2O concentration in biofilters with pH 4.5 and 6.0 was increased to 1.5 and 0.5 ppm, respectively, while no change in the alkalized biofilters. Comparing to communities in step 1, the amoA and nosZ structures were altered when pH was changed to 4.5 and 6.0, but not at 9.5. Abundance of amoA was reduced at pH 4.5, while nosZ abundance was increased with considerably less changes in acidified biofilters compared to alkalized biofilters.

EFFECT OF VENTILATION RATE ON DUST SPATIAL DISTRIBUTION IN A MECHANICALLY VENTILATED AIRSPACE

Dust spatial distribution is an important variable to understand the nature of dust transportation and to implement appropriate control strategies. There is a lack of data on dust spatial distribution in mechanically ventilated airspaces because of lack of adequate sampling techniques. In this project, a multi-point sampler was used to measure the dust spatial distribution at different ventilation rates in a mechanically ventilated airspace, which was an isothermal and two-dimensional flow empty room. Dust mass concentration varied as much as 30-fold between the lowest and the highest within the mechanically ventilated airspace. Ventilation rate had a large effect on the dust spatial distribution. Increasing the ventilation rate reduced the overall mean dust concentration when ventilation rates were lower than 56 air changes/h (ACH). When ventilation rates were higher than 56 ACH in this study, the overall mean dust concentration did not change much (<4%) as the ventilation rate increased by 18%. The spatial gradients of dust concentration become relatively lower as the ventilation rate increases. There is a high dust concentration zone in the ventilated airspace, which is important for selecting proper locations for air cleaning devices.

Fabrication and design of a toxic gas sensor based on polyaniline/titanium dioxide nanocomposite film by layer-by-layer self-assembly

A sensitive polyaniline (PANI)/titanium dioxide (TiO2) based toxic gas sensor deposited on a quartz crystal microbalance (QCM) chip was fabricated and developed through electrostatic layer-by-layer (LbL) self-assembly (SA) with polyaniline and titanium dioxide sol as original materials. The synthesis process and the obtained nanocomposite were confirmed through a home-made measurement set-up, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopic (FTIR) and X-ray diffraction (XRD), which demonstrates that a thin PANI/TiO2 nanocomposite sensing film was successfully achieved by LbL self-assembly. The sensor response was found to be greatly influenced by the number of deposited layers. The resulting PANI/TiO2 based gas sensor exhibited good sensitivity and smooth shift in terms of responses based on frequency data compared to responses based on resistance data. It exhibited high sensitivity toward 10 ppm of three different toxic gases (ammonia, hydrogen sulfide and trimethylamine) with an evident frequency shift and a fast response and recovery time. The sensor showed excellent reversibility and long-term stability as well as good selectivity towards NH3. In real-time application, the obtained PANI/TiO2 based gas sensor exhibited excellent performance and accurate evaluation of three typical foodstuffs. The PANI/TiO2 nanocomposite based gas sensor coated on QCM substrate via LbL self-assembly provides a promising efficient sensor to detect toxic gases in relatively low concentrations.

QUANTIFYING VENTILATION EFFECTIVENESS FOR AIR QUALITY CONTROL

The term “ventilation effectiveness” has been widely used to evaluate ventilation systems for air quality control. The application of the term is often either qualitative, rather than quantitative, or difficult for field application. This paper presents the results of quantification of ventilation effectiveness for specific ventilation systems by using a ventilation effectiveness factor (VEF) and a ventilation effectiveness map (VEM). The VEF and VEM are defined mathematically so they can be used to quantify the ventilation effectiveness of a ventilation system. The application of the VEF and VEM was illustrated using a full–scale room case study, which involves comparison of two different ventilation systems: one had a slot air outlet at the opposite wall to the air inlet (Case A), and the other had a air outlet at the same wall as the air inlet (Case B). It is commonly assumed that the locations of air outlets or exhaust fans have little effect on the ventilation effectiveness for livestock buildings. The case studies show that the outlet location had a substantial effect on the ventilation effectiveness for the room airspace as a whole and for specific locations in the room. The differences in ventilation effectiveness for these two systems were quantified in terms of VEF. Ventilation in Case B is three times as effective at dust removal as in Case A. Ventilation effectiveness factors at specific locations within the airspace were also plotted on a VEM. One of advantages of VEF is that a ventilation system can be its own control for comparison of ventilation effectiveness, instead of requiring a control and a treatment. This feature is particularly useful in system evaluation or troubleshooting because it is often very difficult and expensive to have an identical system to compare.

Product Distribution and Implication of Hydrothermal Conversion of Swine Manure at Low Temperatures

With the goal of utilization of agricultural wastes to produce valuable products, hydrothermal conversion of swine manure at 20% solids content was performed in a 2 L batch reactor at temperatures of 240°C to 280°C, 10 to 120 min reaction time, and 0.7 MPa initial pressure of nitrogen gas. Basically, four types of products (i.e., oil, aqueous product, solid, and gas) were collected from hydrothermal conversion of swine manure with primary material balance. Meanwhile, the raw oil product was distilled and extracted with toluene for accurately quantifying its oil, moisture, and solids content based on ASTM Standards. Results showed that oil yields from swine manure did not vary with reaction temperature and time used in this study, whereas the solid residue, aqueous product, and gas produced from swine manure changed as the temperature and reaction time increased. The results suggested that the hydrothermal conversion of swine manure to oil was a decarboxylation process with an oil yield of 33% by weight at 240°C, which was mainly attributed to the presence of other components in the swine manure, such as lipids, rather than direct hydrothermal conversion of cellulose to oil.

EFFECTS OF ROOM OZONATION ON AIR QUALITY AND PIG PERFORMANCE

Reducing odor emissions from swine farms to avoid complaints about odor nuisance is a major issue. Ozonation has been used to reduce odor in swine buildings, but little research exists on its benefits. A swine-finishing building was divided into two identical rooms and two treatments, ozonation and the control, were applied in a cross-over design. The treatments were switched between rooms every three weeks. The overall experimental period was 12 weeks, during which there were four trials. Pig growth performance, dust mass and size concentration, odor intensity, total sulfur compounds, hydrogen sulfide concentration, ammonia concentration, and total heterotrophic bacterial counts were measured and analyzed during the test period. Sulfur-containing compounds detected included dimethyldisulfide, dimethylsulfide (methanethiol), and dimethyltrisulfide. Ozone application to a swine building at the maximum safe concentration of 0.1 ppm did not have any statistically significant effects on dust mass concentration, odor concentration and emission rate, sulfur compound concentrations, and bacteria counts. However, it did increase ammonia concentration and decrease pig average daily gain. The ozonation effects on hydrogen sulfide concentration could not be evaluated by the gas tube method used during this study.

Discrimination of American ginseng and Asian ginseng using electronic nose and gas chromatography–mass spectrometry coupled with chemometrics

Background American ginseng (Panax quinquefolius L.) and Asian ginseng (Panax ginseng Meyer) products, such as slices, have a similar appearance, but they have significantly different prices, leading to widespread adulteration in the commercial market. Their aroma characteristics are attracting increasing attention and are supposed to be effective and nondestructive markers to determine adulteration. Methods The aroma characteristics of American and Asian ginseng were investigated using gas chromatography–mass spectrometry(GC-MS) and an electronic nose (E-nose). Their volatile organic compounds were separated, classified, compared, and analyzed with different pattern recognition. Results The E-nose showed a good performance in grouping with a principle component analysis explaining 94.45% of variance. A total of 69 aroma components were identified by GC-MS, with 35.6% common components and 64.6% special ingredients between the two ginsengs. It was observed that the components and the number of terpenes and alcohols were markedly different, indicating possible reasons for their difference. The results of pattern recognition confirmed that the E-nose processing result is similar to that of GC-MS. The interrelation between aroma constituents and sensors indicated that special sensors were highly related to some terpenes and alcohols. Accordingly, the contents of selected constituents were accurately predicted by corresponding sensors with most R2 reaching 90%. Conclusion Combined with advanced chemometrics, the E-nose is capable of discriminating between American and Asian ginseng in both qualitative and quantitative angles, presenting an accurate, rapid, and nondestructive reference approach.