Optimization of the fermentation media and growth conditions of Bacillus velezensis BHZ-29 using a Plackett-Burman design experiment combined with response surface methodology.

Introduction: Bacillus velezensis occurs extensively in the soil environment. It produces a range of antimicrobial compounds that play an important role in the field of biological control. However, during the actual application process it is often affected by factors such as the medium formulation and fermentation conditions, and therefore biocontrol measures often do not achieve their expected outcomes. Methods: In this study, the B. velezensis BHZ-29 strain was used as the research object. The carbon and nitrogen sources, and inorganic salts that affect the number of viable bacteria and antibacterial potency of B. velezensis BHZ-29, were screened by a single factor test. A Plackett-Burman design experiment was conducted to determine the significant factors affecting the number of viable bacteria and antibacterial potency, and a Box-Behnken design experiment was used to obtain the optimal growth of B. velezensis BHZ-29. The medium formula that produced the highest number of viable bacteria and most antibacterial substances was determined. The initial pH, temperature, amount of inoculant, liquid volume, shaking speed, and culture time were determined by a single factor test. The factors that had a significant influence on the number of viable bacteria of B. velezensis BHZ-29 were selected by an orthogonal test. A Box-Behnken design experiment was conducted to obtain the optimal fermentation conditions, and highest number of viable bacteria and antibacterial titer. Results: Molasses, peptone, and magnesium sulfate had significant effects on the viable count and antibacterial titer of B. velezensis BHZ-29. The viable count of B. velezensis BHZ-29 increased from 7.83 × 109 to 2.17 × 1010 CFU/mL, and the antibacterial titer increased from 111.67 to 153.13 mm/mL when the optimal media were used. The optimal fermentation conditions for B. velezensis BHZ-29 were as follows: temperature 25.57°C, pH 7.23, culture time 95.90 h, rotation speed 160 rpm, amount of inoculant 2%, and liquid volume 100 ml. After the optimization of fermentation conditions, the number of viable bacteria increased to 3.39 × 1010 CFU/mL, and the bacteriostatic titer increased to 158.85 mm/ml.The plant height and leaf number of cotton plants treated with BHZ-29 fermentation broth were higher than those of cotton inoculated with Verticillium dahliae. The number of bacteria was 1.15 × 107 CFU/g, and the number of fungi was 1.60 × 105 spores/g. The disease index of the cotton seedlings treated with the optimized fermentation broth was 2.2, and a control effect of 93.8% was achieved. B. velezensis BHZ-29 could reduce the disease index of cotton Verticillium wilt and had a controlling effect on the disease. The best effect was achieved in the treatment group with an inoculation concentration of 2 × 108 CFU/ml, the disease index was 14.50, and a control effect of 84.18% was achieved. Discussion: The fermentation process parameters of the number of viable bacteria and antibacterial titer by strain B. velezensis BHZ-29 were optimized to lay a foundation for the practical production and application of strain B. velezensis BHZ-29 in agriculture.

Analysis of the virulence, infection process, and extracellular enzyme activities of Aspergillus nomius against the Asian corn borer, Ostrinia furnacalis guenée (Lepidoptera: Crambidae).

The control of Ostrinia furnacalis, a major pest of maize in Xinjiang, is challenging owing to the occurrence of resistant individuals. Entomopathogenic fungi (EPF) are natural insect regulators used as substitutes for synthetic chemical insecticides. The fungus Aspergillus nomius is highly pathogenic to O. furnacalis; however, its virulence characteristics have not been identified. This study aimed to analyse the lethal efficacy, mode of infection on the cuticle, and extracellular enzyme activity of A. nomius against O. furnacalis. We found that the mortality and mycosis of O. furnacalis were dose-dependent when exposed to A. nomius and varied at different life stages. The egg-hatching and adult emergence rates decreased with an increase in conidial suspension. The highest mortality (83.33%, 7 d post-infection [DPI]) and mycosis (74.33%, 7 DPI) and the lowest mortality response (8.52 × 103 conidia mL-1) and median lethal time (4.91 d) occurred in the 3rd instar larvae of O. furnacalis. Scanning electron microscopy indicated that numerous conidia germination and infection structure formation may have contributed to the high pathogenicity of A. nomius against O. furnacalis. There were significant correlations between O. furnacalis mortality and the activities of extracellular protease, lipase, and chitinase of A. nomius. This study revealed the infection process of the highly pathogenic A. nomius against O. furnacalis, providing a theoretical basis and reference for strain improvement and field application of EPF.

Sources and environmental fate of halomethoxybenzenes.

Halomethoxybenzenes are pervasive in the atmosphere at concentration levels that exceed, often by an order of magnitude, those of the persistent organic pollutants with which they share the attributes of persistence and potential for long-range transport, bioaccumulation, and toxic effects. Long ignored by environmental chemists because of their predominantly natural origin-namely, synthesis by terrestrial wood-rotting fungi, marine algae, and invertebrates-knowledge of their environmental pathways remains limited. Through measuring the spatial and seasonal variability of four halomethoxybenzenes in air and precipitation and performing complementary environmental fate simulations, we present evidence that these compounds undergo continental-scale transport in the atmosphere, which they enter largely by evaporation from water. This also applies to halomethoxybenzenes originating in terrestrial environments, such as drosophilin A methyl ether, which reach aquatic environments with runoff, possibly in the form of their phenolic precursors. Our findings contribute substantially to the comprehension of sources and fate of halomethoxybenzenes, illuminating their widespread atmospheric dispersal.

Field Calibration and PAS-SIM Model Evaluation of the XAD-Based Passive Air Sampler for Semi-Volatile Organic Compounds.

The use of passive air samplers (PAS) for semi-volatile organic compounds (SVOCs) continues to expand. To advance quantitative understanding of uptake kinetics, we calibrated the XAD-PAS, using a styrene-divinylbenzene sorbent, through a year-long side-by-side deployment with an active sampler. Twelve XAD-PASs, deployed in June 2020, were retrieved at 4-week intervals, while gas phase SVOCs were quantified in 48 consecutive week-long active samples taken from June 2020 to May 2021. Consistent with XAD's high uptake capacity, even relatively volatile SVOCs, such as hexachlorobutadiene, displayed linear uptake throughout the entire deployment. Sampling rates (SRs) range between 0.1 and 0.6 m3 day-1 for 26 SVOCs, including brominated flame retardants, organophosphate esters, and halogenated methoxylated benzenes. SRs are compared with experimental SRs reported previously. The ability of the existing mechanistic uptake model PAS-SIM to reproduce the observed uptake and SRs was evaluated. Agreement between simulated and measured uptake curves was reasonable but varied with compound volatility and the assumed stagnant air layer boundary thickness. Even though PAS-SIM succeeds in predicting the SR range for the studied SVOCs, it fails to capture the volatility dependence of the SR by underestimating the length of the linear uptake period and by failing to consider the kinetics of sorption.

A multi-pathway exposure assessment for polycyclic aromatic hydrocarbons among residents in the Athabasca oil sands region, Canada.

Due to increasing emissions from ongoing development of the oil sands in Northern Alberta, Canada, there is concern that local residents and organisms are experiencing elevated exposures to hazardous contaminants. We modified an existing human bioaccumulation model (ACC-Human) to represent the local food chain in the Athabasca oil sands region (AOSR), the focus of oil sands development in Alberta. We used the model to assess the potential exposure to three polycyclic aromatic hydrocarbons (PAHs) among local residents that have a high intake of locally sourced traditional foods. To place these estimates into context, we complemented them with estimated PAH intake through market foods and smoking. Our approach was able to produce realistic body burdens of the PAHs in aquatic and terrestrial wildlife and in humans, both in magnitude and with respect to the relative difference between smokers and non-smokers. Over the model simulation period (1967-2009), market food was the dominant dietary exposure route for phenanthrene and pyrene, while local food, and in particular local fish, dominated the intake of benzo[a]pyrene. Exposure to benzo[a]pyrene therefore was also predicted to increase over time in concert with expanding oil sands operations. Those smoking at the average rate of Northern Albertans take in an additional amount of all three PAHs that is at least as large as dietary intake. Estimated daily intake rates are below toxicological reference thresholds for all three PAHs. However, daily intake of BaP in adults is only ∼20 fold below those thresholds and is predicted to increase. Key uncertainties in the assessment included the effect of food preparation on the PAH content in food (e.g., smoking of fish), the limited availability of market food contamination data specific to Canada, and the PAH content of the vapor phase of first-hand cigarette smoke. Considering the satisfactory model evaluation, ACC-Human AOSR should be suited to making predictions of future contaminant exposure based on development scenarios in the AOSR or in response to potential emission reduction efforts. It should also be applicable to other organic contaminants of concern released by oil sands operations.

Release Mechanism of Short- and Medium-Chain Chlorinated Paraffins from PVC Materials under Thermal Treatment.

Chlorinated paraffins (CPs) as plasticizers are massively added to polyvinyl chloride (PVC) products, during whose life cycle CPs can be continuously released especially under thermal stress. In this study, a PVC cable sheath was adopted as a representative kind of PVC material to investigate the release behaviors of short- and medium-chain CPs (SCCPs and MCCPs) under thermal treatment. Release percentages of CPs with increasing temperature followed a Gaussian-like curve. At the unmolten stage of 80 °C, heating for 10 min caused 0.051% of added SCCPs and 0.029% of added MCCPs to be released. At the molten stage of 270 °C, accumulative release rates of SCCPs and MCCPs within 10 min were up to 30 and 14%, respectively. The developed emission model indicated that material-gas partitioning and internal diffusion simultaneously governed the release of CPs. During thermal treatment, the release of CPs could be remarkably affected by the thermal expansion of the PVC material and the formation of breakage and micropores. Congener group profiles of released CPs indicated a slight fractionation effect for SCCPs during the release process. Furthermore, the release risk of CPs from the whole life cycle of PVC products was preliminarily evaluated.

Molecular identification and efficacy of entomopathogenic fungi isolates against larvae of the Asian corn borer Ostrinia furnacalis (Lepidoptera: Crambidae) in Xinjiang, China.

AIMS: This study aimed to isolate and identify entomopathogenic fungi (EPF) from fungus-infected Ostrinia furnacalis larvae, screen their bio-efficacy against O. furnacalis, and select the most suitable virulent native EPF for biocontrol agent development. METHODS AND RESULTS: The occurrence of EPF isolated from various maize production regions in Xinjiang was investigated. Of 13,864 O. furnacalis cadavers surveyed, 536 were selected, and of 136 fungal specimens collected, 14 species were identified. Four fungal isolates were highly pathogenic to O. furnacalis: Aspergillus sp., Lecanicillium attenuatum, Beauveria bassiana and Penicillium polonicum. The Aspergillus sp. was the most abundant (42.25% distribution frequency). Bioassay results revealed that it was as pathogenic as B. bassiana (positive control), with 96.58% lethality against O. furnacalis (LC50 : 1.40 × 104 conidia ml-1 , LT50 : 3.41 days). Through morphological examination and rDNA-benA and rDNA-CaM homogeneity analyses, the isolate was identified as Aspergillus nomius. CONCLUSIONS: Four EPF species were highly pathogenic, with A. nomius being the most prevalent in Xinjiang. A. nomius is a potential biocontrol agent. SIGNIFICANCE AND IMPACT OF STUDY: For sustainable prevention and control of O. furnacalis infestation, identifying biocontrol agents with high virulence against O. furnacalis is crucial. The findings of this study support the development of EPF-based biocontrol approaches.

Global Historical Production, Use, In-Use Stocks, and Emissions of Short-, Medium-, and Long-Chain Chlorinated Paraffins.

The last few decades have seen ubiquitous and increasing contamination of chlorinated paraffins (CPs) worldwide. Here, we develop the first global inventories of production, use, in-use stocks, and emissions of total CPs, including the short-, medium- and long-chain components (SCCPs, MCCPs, and LCCPs) during 1930-2020 using a dynamic substance flow analysis model named Chemical in Products Comprehensive Anthroposhpheric Fate Estimation. The model estimates that a total of ∼33 million metric tons of CPs have been produced and used globally, ∼40% of which still resided in in-use products by 2020 and is available for long-term emissions in the next decades. Global cumulative emissions of CPs have increased to ∼5.2 million metric tons by 2020, with SCCPs, MCCPs, and LCCPs accounting for ∼30, 40, and 30%, respectively. While the production, use, and emissions of CPs started declining in regions such as Western Europe, they remain high in China. The model also suggests that homologues with 10, 14, and 22-23 carbons were predominant in the cumulatively produced and emitted SCCPs, MCCPs, and LCCPs, respectively. The emission estimates were evaluated by generating environmental concentrations that are comparable to literature-reported environmental monitoring data. Our estimates provide opportunities to link the environmental fate and occurrence of CPs to emission sources and lay the basis for future risk-reduction strategies of CPs around the world.

Mechanistic aspects of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) formation from chlorine bleaching of non-wood pulp.

Chlorine bleaching of non-wood pulp can produce and release polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) into environment. In this study, a series of chlorination experiments were conducted to explore the source, formation pathway and formation kinetics of Cl1-8DD/Fs during the chlorine bleaching of wheat straw pulp. The 13C isotope-labeling experiment verified that PCDD/Fs could not be formed from the chlorination of phenols in pulp. Above 80% of the observed PCDFs originated from the direct chlorination of dibenzofuran (DBF) in unbleached wheat straw pulp, while approximately 60% of the observed PCDDs came from the chlorination of nonextractable precursors in the pulp. The yield of total PCDFs was 2 orders of magnitude higher than that of total PCDDs. The kinetic study indicated that DBF was more easily chlorinated than dibenzo-p-dioxin (DBD) in the pulp solution. Pseudo-first-order reaction kinetic equations fitted the formation and degradation of PCDD/Fs well. The direct chlorination of DBD/F primarily preferred a selective pattern at the 2 position, followed by the 8, 7 and 3 positions. A higher content of DBF in unbleached pulp led to a higher yield of 2,3,7,8-Cl4DF. Finally, the practical implication for dioxin formation control was discussed.

Release and Transformation of BTBPE During the Thermal Treatment of Flame Retardant ABS Plastics.

Thermal scenarios inevitably occur during the lifecycle of engineering plastics laden with brominated flame retardants (BFRs). However, little information on the fate of embedded BFRs during the thermal processes is available. In this study, we measured the release and transformation of a typical BFR, 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), during the thermal treatment of acrylonitrile butadiene styrene (ABS) plastics. The possible thermal scenarios were simulated by varying the heating temperature and atmosphere. The maximum release rate of BTBPE was observed at 350 °C. A release kinetic model was developed to explore the mechanism of BTBPE release while heating ABS. Material-phase diffusion was found to be the rate-determining step during release. According to the developed release model, it was estimated that 0.04-0.17% of embedded BTBPE could be released to air during the industrial processing of ABS plastics. When the heating temperature was ≥350 °C, approximately 15-56% of embedded BTBPE decomposed to bromophenols (BPs) and 1,3,5-tribromo-2-(vinyloxy) benzene (TBVOB), and the decomposition followed a first-order kinetics at 350 °C. Polybrominated dibenzo- p-dioxins and dibenzofurans (PBDD/Fs) were also significantly formed at ≥350 °C from BPs and TBVOB via a precursor mechanism. A higher temperature (≥450 °C) was favorable for the formation of PBDFs.

Pontibacter brevis sp. nov., isolated from rhizosphere soil of Tamarix ramosissima.

A Gram-stain-negative, oval-shaped and light pink pigmented bacterium, designated XAAS-2T, was isolated from rhizosphere soil of Tamarix ramosissima. The sole respiratory quinone of the type strain XAAS-2T was MK-7, and the principal cellular fatty acids were summed feature 4 (iso-C17 : 1 I and/or anteiso-C17 : 1 B) and iso-C15 : 0. The major polar lipids were phosphatidylethanolamine and two unidentified lipids. 16S rRNA gene sequence analysis indicated that strain XAAS-2T belonged to the genus Pontibacter within the family Cytophagaceae with sequence similarities of 93.9-97.1 % to other type species of the genus Pontibacter and to Pontibacter xinjiangensis CCTCC AB 207200T as the closest neighbour. The DNA G+C content of strain XAAS-2T was 50.6 mol%. The level of DNA-DNA relatedness of XAAS-2T and P. xinjiangensis CCTCC AB 207200T was 47.5 % (sd=3.27). Phenotypic and genotypic data suggested that strain XAAS-2T represents a novel species of the genus Pontibacter, for which the name Pontibacterbrevis sp. nov. is proposed, with the type strain XAAS-2T (=CCTCC AB 2016135T=JCM 31443T).

Release and Gas-Particle Partitioning Behaviors of Short-Chain Chlorinated Paraffins (SCCPs) During the Thermal Treatment of Polyvinyl Chloride Flooring.

Chlorinated paraffin (CP) mixture is a common additive in polyvinyl chloride (PVC) products as a plasticizer and flame retardant. During the PVC plastic life cycle, intentional or incidental thermal processes inevitably cause an abrupt release of short-chain CPs (SCCPs). In this study, the thermal processing of PVC plastics was simulated by heating PVC flooring at 100-200 °C in a chamber. The 1 h thermal treatment caused the release of 1.9-10.7% of the embedded SCCPs. A developed emission model indicated that SCCP release was mainly controlled by material-gas partitioning at 100 °C. However, release control tended to be subjected to material-phase diffusion above 150 °C, especially for SCCP congeners with shorter carbon-chain lengths. A cascade impactor (NanoMoudi) was used to collect particles of different sizes and gas-phase SCCPs. The elevated temperature resulted in a higher partition of SCCPs from the gas-phase to particle-phase. SCCPs were not strongly inclined to form aerosol particles by nucleation, and less present in the Aitken mode particles. Junge-Pankow adsorption model well fitted the partitioning of SCCPs between the gas-phase and accumulation mode particles. Inhalation exposure estimation indicated that PVC processing and recycling workers could face a considerably high risk for exposure to SCCPs.

Concentrations of short- and medium-chain chlorinated paraffins in indoor dusts from malls in China: Implications for human exposure.

Levels and distribution of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) were measured in indoor dusts from malls in China. The concentrations of SCCPs and MCCPs in dustfalls from a building material mall ranged from 6.0 to 361.4 µg g-1 and from 5.0 to 285.9 µg g-1, respectively. Much heavier contamination was found in central air conditioner filter (CACF) dusts from a newly opened shopping mall, with SCCP concentrations of 114.7-707.0 µg g-1 and MCCP concentrations of 89.0-1082.9 µg g-1. The C13- and C14-CPs were the dominant congeners, while the Cl7 and Cl8 groups were the major chlorine congeners in both kinds of dust samples. Significant correlation relationships (p ≤ 0.05) were found between ∑SCCPs and ∑MCCPs in CACF dusts and dustfalls. Varied exposure pathways including dust ingestion and dermal permeation have been evaluated. The average daily exposure doses of SCCPs and MCCPs for the adult in CACF dusts and dustfalls were estimated to be 0.394 and 0.150 µg kg-1 day-1, respectively. The toddler had higher exposure risks with 5.918 and 2.658 µg kg-1 day-1 in the shopping and building material malls, respectively. Dermal permeation was the predominated exposure pathway for the adult, while dust ingestion was suggested to be more important for the toddler due to hand-to-mouth contact.

Dispersion of Short- and Medium-Chain Chlorinated Paraffins (CPs) from a CP Production Plant to the Surrounding Surface Soils and Coniferous Leaves.

Chlorinated paraffin (CP) production is one important emission source for short- and medium-chain CPs (SCCPs and MCCPs) in the environment. In this study, 48 CP congener groups were measured in the surface soils and coniferous leaves collected from the inner and surrounding environment of a CP production plant that has been in operation for more than 30 years to investigate the dispersion and deposition behavior of SCCPs and MCCPs. The average concentrations of the sum of SCCPs and MCCPs in the in-plant coniferous leaves and surface soils were 4548.7 ng g-1 dry weight (dw) and 3481.8 ng g-1 dw, which were 2-fold and 10-fold higher than those in the surrounding environment, respectively. The Gaussian air pollution model explained the spatial distribution of CPs in the coniferous leaves, whereas the dispersion of CPs to the surrounding surface soils fits the Boltzmann equation well. Significant fractionation effect was observed for the atmospheric dispersion of CPs from the production plant. CP congener groups with higher octanol-air partitioning coefficients (KOA) were more predominant in the in-plant environment, whereas the ones with lower KOA values had the elevated proportion in the surrounding environment. A radius of approximately 4 km from the CP production plant was influenced by the atmospheric dispersion and deposition of CPs.

[Bacteria diversity of soil of Populus Euphratica forest in the hinterland of Taklimakan desert].

OBJECTIVE: The aim of study was to investigate bacterial diversity of Populus Euphratica forest in the hinterland of Taklimakan desert. All the isolateds were be used as inoculants for silage and biofertilizer. METHODS: Strains were isolated by culture-dependent method. Gram staining, NaCl tolerance,enzyme activity (including amylase, esterase, cellulase) were determined by strand methods. Phylogenetic trees based on 16S rRNA gene sequences were constructed by using the neighbour-joining. RESULTS: A total of 27 strains were obtained. Phylogenetic analysis of the bacterial 16S rRNA gene showed that all isolates fell into one of the following four bacterial lineages: Actinobacteria (16 strains), Proteobacteria (4 strains), Firmicutes (6 strains) and Bacteroidetes (1 strains). Gram staining indicated that 5 strains were gram-negative and the others were gram-positive. Among these, 15 strains showed amylase activity, 9 strains showed esterase activity and 9 strains showed cellulase activity. All strains growth occurred at in presence of 2% NaCl, 22 strains growth occurred at in presence of 5% NaCl and only 1 strain tolerated up to 15% NaCl. CONCLUSION: The bacterial population diversity is abundant in soil of Populus Euphratica Forest in the hinterland of Taklimakan Desert, which is worthy of further investigation.