A new headspace solid-phase microextraction coupled with gas chromatography-tandem mass spectrometry method for the simultaneous quantification of 21 microbial volatile organic compounds in urine and blood

Microbial volatile organic compounds measured in the air of a waste sorting plant and a university by thermal desorption-gas chromatography-tandem mass spectrometry

In recyclable waste management facilities, several contaminants, mainly bioaerosols and microorganisms, can be released and cause potential adverse health effects. Given that microbial volatile organic compounds (mVOCs) are metabolites developed by molds and since they can be considered as potential biomarkers of mold exposure, their concentrations in ambient air were monitored at a recyclable waste sorting plant (WSP) and a university campus (UC) serving as control environment for comparison. A recently developed analytical method was used for the detection of 21 selected mVOCs in real conditions. The impact of mVOC sampling duration, period of the day, and variability of their concentrations between different workstations at both sites was studied. At UC, only 3 mVOCs were detected in comparison with 13 mVOCs at the WSP. The sampling duration of 2 h was chosen to increase the sensitivity of the method. Statistical tests showed no significant difference in concentration for the detected mVOCs at WSP for different period of the day whereas an increase in concentrations for ethyl acetate was observed at UC. At WSP, the highest concentrations were measured at the pre-sorting room (ex. 4.04 ng/m3 for pentan-2-one), followed by the sorting room (ex. 3.46 ng/m3 for decanal), the optic sorting room (ex. 3.67 ng/m3 for pentan-2-one), and the lowest concentrations were measured at the waste reception area (ex. 0.51 ng/m3 for cyclopentanone). This study allows the optimization of the mVOC sampling method, the comparison of the mVOC profiles between contaminated and non-contaminated workplaces and the recommendation for mVOCs with better potential as biomarkers of mold exposure.

A matrix-centered view of mass spectrometry platform innovation for volatilome research

Volatile organic compounds (VOCs) are carbon-containing molecules with high vapor pressure and low water solubility that are released from biotic and abiotic matrices. Because they are in the gaseous phase, these compounds tend to remain undetected when using conventional metabolomic profiling methods. Despite this omission, efforts to profile VOCs can provide useful information related to metabolic status and identify potential signaling pathways or toxicological impacts in natural or engineered environments. Over the past several decades mass spectrometry (MS) platform innovation has instigated new opportunities for VOC detection from previously intractable matrices. In parallel, volatilome research linking VOC profiles to other forms of multi-omic information (DNA, RNA, protein, and other metabolites) has gained prominence in resolving genotype/phenotype relationships at different levels of biological organization. This review explores both on-line and off-line methods used in VOC profiling with MS from different matrices. On-line methods involve direct sample injection into the MS platform without any prior compound separation, while off-line methods involve chromatographic separation prior to sample injection and analyte detection. Attention is given to the technical evolution of platforms needed for increasingly resolved VOC profiles, tracing technical progress over time with particular emphasis on emerging microbiome and diagnostic applications.

A novel fluorescent aptasensor for sensitive and selective detection of environmental toxins fumonisin B1 based on enzyme-assisted dual recycling amplification and 2D δ-FeOOH-NH2 nanosheets

Fumonisin (FB) is a pervasive hazardous substance in the environment, presenting significant threats to human health and ecological systems. Thus, the selective and sensitive detection of fumonisin B1 (FB1) is crucial due to its high toxicity and wide distribution in corn, oats, and related products. In this work, we developed a novel and versatile fluorescent aptasensor by combining enzyme-assisted dual recycling amplification with 2D δ-FeOOH-NH2 nanosheets for the determination of FB1. The established CRISPR/Cas12a system was activated by using activator DNA (aDNA), which was released via a T7 exonuclease-assisted recycling reaction. Additionally, the activated Cas12a protein was utilized for non-specifically cleavage of the FAM-labeled single-stranded DNA (ssDNA-FAM) anchored on δ-FeOOH-NH2 nanosheets. The pre-quenched fluorescence signal was restored due to the desorption of the cleaved ssDNA-FAM. Due to the utilization of this T7 exonuclease-Cas12a-δ-FeOOH-NH2 aptasensor for signal amplification, the detection range of FB1 was expanded from 1 pg/mL to 100 ng/mL, with a limit of detection (LOD) as low as 0.45 pg/mL. This study not only provides novel insights into the development of fluorescence biosensors based on 2D nanomaterials combined with CRISPR/Cas12a, but also exhibits remarkable applicability in detecting other significant targets.

Determination of blood:air, urine:air and plasma:air partition coefficients of selected microbial volatile organic compounds

Partition coefficients (PCs) are essential parameters for understanding the toxicokinetics of chemicals in the human body since they are used in the description of different processes of absorption, distribution, and excretion in physiologically based pharmacokinetic (PBPK) models used in chemical exposure and risk assessment. The goal of this study was to determine urine:air, blood:air and plasma:air partition coefficients (PCs) of microbial volatile organic compounds (mVOCs) previously selected as having high potential as biomarkers of indoor mold exposure. To achieve this goal, the vial-equilibration technique was used, and quantification was performed using headspace gas chromatography tandem mass spectrometry (HS-GC-MS/MS) analysis. Matrix:air PCs of 19 different mVOCs have been successfully determined and their values ranged between 14 and 3586 for urine:air, 78 and 4721 for blood:air and 64 and 5604 for plasma:air PCs. Water:air PCs were also determined, and their values varied between 16 and 2210, showing a good correlation with urine:air PCs for 17 compounds of the selected mVOCs (R2 = 0.97, slope close to unity) indicating that water:air PCs below 103 may be a good surrogate for urine:air PCs. All studied mVOCs have high blood:air PCs (greater than 78) indicating strong pulmonary uptake. Due to their high blood:urine PCs, some mVOCs may be more easily measured in blood than in urine. This work is an important preliminary step toward the use of mVOCs as potential biomarkers of indoor mold exposure. The data obtained in this study will help to determine the most appropriate matrix to use in this biomonitoring approach and will eventually facilitate the development of PBPK models for these chemicals.

Microbial volatile organic compounds as novel indicators of anaerobic digestion instability: Potential and challenges

The wide application of anaerobic digestion (AD) technology is limited by process fluctuations. Thus, process monitoring based on screening state parameters as early warning indicators (EWI) is a top priority for AD facilities. However, predicting anaerobic digester stability based on such indicators is difficult, and their threshold values are uncertain, case-specific, and sometimes produce conflicting results. Thus, new EWI should be proposed to integrate microbial and metabolic information. These microbial volatile organic compounds (mVOCs) including alkanes, alkenes, alkynes, aromatic compounds are produced by microorganisms (bacteria, archaea and fungi), which might serve as a promising diagnostic tool for environmental monitoring. Moreover, mVOCs diffuse in both gas and liquid phases and are considered the language of intra kingdom microbial interactions. Herein, we highlight the potential of mVOCs as EWI for AD process instability, including discussions regarding characteristics and sources of mVOCs as well as sampling and determination methods. Furthermore, existing challenges must be addressed, before mVOCs profiling can be used as an early warning system for diagnosing AD process instability, such as mVOCs sampling, analysis and identification. Finally, we discuss the potential biotechnology applications of mVOCs and approaches to overcome the challenges regarding their application.

From salty to thriving: plant growth promoting bacteria as nature's allies in overcoming salinity stress in plants

Soil salinity is one of the main problems that affects global crop yield. Researchers have attempted to alleviate the effects of salt stress on plant growth using a variety of approaches, including genetic modification of salt-tolerant plants, screening the higher salt-tolerant genotypes, and the inoculation of beneficial plant microbiome, such as plant growth-promoting bacteria (PGPB). PGPB mainly exists in the rhizosphere soil, plant tissues and on the surfaces of leaves or stems, and can promote plant growth and increase plant tolerance to abiotic stress. Many halophytes recruit salt-resistant microorganisms, and therefore endophytic bacteria isolated from halophytes can help enhance plant stress responses. Beneficial plant-microbe interactions are widespread in nature, and microbial communities provide an opportunity to understand these beneficial interactions. In this study, we provide a brief overview of the current state of plant microbiomes and give particular emphasis on its influence factors and discuss various mechanisms used by PGPB in alleviating salt stress for plants. Then, we also describe the relationship between bacterial Type VI secretion system and plant growth promotion.