Research advances of SERS analysis method based on silent region molecules for food safety detection.

Food safety is a critical issue that is closely related to people's health and safety. As a simple, rapid, and sensitive detection technique, surface-enhanced Raman scattering (SERS) technology has significant potential for food safety detection. Recently, researchers have shown a growing interest in utilizing silent region molecules for SERS analysis. These molecules exhibit significant Raman scattering peaks in the cellular Raman silent region between 1800 and 2800 cm-1 avoiding overlapping with the SERS spectrum of biological matrices in the range 600-1800 cm-1, which could effectively circumvent matrix effects and improve the SERS accuracy. In this review, the application of silent region molecules-based SERS analytical technique for food safety detection is introduced, detection strategies including label-free detection and labeled detection are discussed, and recent applications of SERS analysis technology based on molecules containing alkyne and nitrile groups, as well as Prussian blue (PB) in the detection of pesticides, mycotoxins, metal ions, and foodborne pathogens are highlighted. This review aims to draw the attention to the silent region molecules-based SERS analytical technique and to provide theoretical support for its further applications in food safety detection.

Exploring the Aroma Fingerprint of Various Chinese Pear Cultivars through Qualitative and Quantitative Analysis of Volatile Compounds Using HS-SPME and GC×GC-TOFMS.

To comprehensively understand the volatile compounds and assess the aroma profiles of different types of Pyrus ussuriensis Maxim. Anli, Dongmili, Huagai, Jianbali, Jingbaili, Jinxiangshui, and Nanguoli were detected via headspace solid phase microextraction (HS-SPME) coupled with two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC-TOFMS). The aroma composition, total aroma content, proportion and number of different aroma types, and the relative quantities of each compound were analyzed and evaluated. The results showed that 174 volatile aroma compounds were detected in various cultivars, mainly including esters, alcohols, aldehydes, and alkenes: Jinxiangshui had the highest total aroma content at 2825.59 ng/g; and Nanguoli had the highest number of aroma species detected at 108. The aroma composition and content varied among pear varieties, and the pears could be divided into three groups based on principal component analysis. Twenty-four kinds of aroma scents were detected; among them, fruit and aliphatic were the main fragrance types. The proportions of aroma types also varied among different varieties, visually and quantitatively displaying changes of the whole aroma of the different varieties of pears brought by the changes in aroma composition. This study contributes to further research on volatile compound analysis, and provides useful data for the improvement of fruit sensory quality and breeding work.

A sensitive and simple competitive nanozyme-linked apta-sorbent assay for the dual-mode detection of ochratoxin A.

The enzyme-linked apta-sorbent assay (ELASA) is widely used for the detection of small-molecule compounds as a result of low cost and reagent stability of aptamers. However, enzyme labels used in ELASA still suffer from some drawbacks, such as high production cost and limited stability. To overcome the drawbacks, we reported a nanozyme-linked apta-sorbent assay (NLASA) coupled with surface-enhanced Raman scattering (SERS)-colorimetric dual-mode detection. For nanozyme labels, Pd-Pt bimetallic nanocrystals (Pd-Pt NRs) could catalyze 3,3',5,5'-tetramethylbenzidine (TMB) to blue TMB2+, whose color variation could not only be distinguished by naked eyes but also had a strong SERS signal. The NLASA method was employed to detect ochratoxin A (OTA) with a limit of detection values of 0.097 nM (0.039 ppb) and 0.042 nM (0.017 ppb) via the colorimetric and SERS methods, respectively. This method was applied for the determination of OTA in wine and grape samples, and the detection results were in a satisfied agreement with those determined by the high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method. The proposed NLASA method provided a rapid and sensitive detection for OTA and could also be broadened for other small-molecules.

Analysis of Volatile Compounds in Pears by HS-SPME-GC×GC-TOFMS.

Aroma plays an important role in fruit quality and varies among different fruit cultivars. In this study, a sensitive and accurate method based on headspace solid-phase microextraction (HS-SPME) coupled with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was developed to comprehensively compare aroma components of five pear cultivars. In total, 241 volatile compounds were identified and the predominant volatile compounds were esters (101 compounds), followed by alcohols (20 compounds) and aldehydes (28 compounds). The longyuanyangli has the highest relative concentration (838.12 ng/g), while the Packham has the lowest (208.45 ng/g). This study provides a practical method for pear aroma analysis using SPME and GC×GC-TOFMS.

Determination and risk assessment of sixteen polycyclic aromatic hydrocarbons in vegetables.

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic environmental pollutants posing a potential risk to human health. This study was constructed to investigate the presence of 16 PAHs in six commonly consumed vegetables collected from the markets in Shandong, China by a quick, easy, cheap, effective, rugged, safe (QuEChERS)-based extraction method coupled with gas chromatography-mass spectrometry (GC-MS). Our results showed that the vegetables were polluted with PAHs at an alarming level, of which celery contained the highest total concentration of PAHs (Σ16 PAH), whereas cucumbers contained the lowest Σ16 PAH. Besides, the dietary exposure of PAHs was assessed in these vegetables based on the maximum Σ16 PAH. The results showed that the populations in Shandong were exposed to 23-213 ng/d of PAHs through these six vegetables, suggesting that vegetables are the major sources of PAHs in the diet. Hence, it is necessary to monitor the PAH levels in vegetables. Our study provides guidance for future legislative actions regarding PAH levels in vegetables in China.

Residues and dissipation kinetics of carbendazim and diethofencarb in tomato (Lycopersicon esculentum Mill.) and intake risk assessment.

Dissipation behaviors and residues of carbendazim and diethofencarb in combination in tomato were investigated. The half-lives were 2.1-3.4 days for carbendazim, and 1.8-3.2 days for diethofencarb at a dose of 1.5 times of the recommended dosage. The residues of carbendazim and diethofencarb were below the maximum residue limits (MRLs) in China one day after application of the combination. The ultimate residues were significantly lower than the maximum permissible intake (MPI) in China at the recommended high dose for both child and adult. The values of the maximum dietary exposure for carbendazim and diethofencarb were 0.26 and 0.27 mg per person per day, respectively. The theoretical maximum daily intake (TMDI) values for carbendazim and diethofencarb were 1.5 and 0.5 mg/day, respectively. The dietary exposure was lower than the MPI, which indicates the harvested tomato samples under the experimental conditions (open field) are safe for human consumption at the recommended high dosage of the wettable powder.

Monitoring and probabilistic risk assessment of chlorothalonil residues in vegetables from Shandong province (China).

The aims of this study were to investigate the contamination status of chlorothalonil pesticide residues in vegetables from Shandong province, and to assess the potential risk of chlorothalonil to consumers based on vegetable consumption and body weight using an improved non-parameter probabilistic model. The results showed that Young children (8 months-6 years old) were more sensitive than General population(above 1year-old). In general, the health risk of chlorothalonil residues to 2 consumer groups via vegetable exposure was low, and the level of residual chlorothalonil was below the Acute Reference Dose (ARfD). This result would provide useful information for re-evaluating pesticides and for revising the chlorothalonil standard in vegetables.

Risk assessment of pesticide residues in dietary intake of celery in China.

OBJECTIVE: Residue risk assessment of pesticides in celery was conducted to provide a scientific basis for agricultural regulation policies and working procedures. METHODS: Three hundred samples from eight main growing regions in China were collected and pesticide residue analyses were performed using GC-MS/MS and LC-MS/MS methods. Both chronic and acute intake risk of pesticides were assessed. Furthermore, intake risk of each detected pesticide was ranked according to a predefined ranking matrix. RESULTS: (1) Out of these 300 samples, 175 were revealed to contain one or more pesticide residues. Twenty-five pesticides were identified in total, out of which, carbofuran was found to exceed the maximum residue limit. (2) Chronic and acute intake risks were evaluated and lie in between 0 and 1.80 and between 0.05 and 28.0 for these twenty-five pesticides, respectively. (3) Intake risk of individual pesticide was ranked; five pesticides, including avermectin, triazophos, chlorpyrifos, dimethoate oxygen, and carbofuran posed the highest risks. CONCLUSION: Pesticide residues were detected in more than 58% celery samples in our study. Most pesticides have a residue level lower than their maximum residue limit and pose low chronic and acute dietary intake risk. However, usage of some pesticides like carbofuran should be closely monitored and regulated in the future.

Lipidomic and transcriptomic analysis of the increase in eicosapentaenoic acid under cobalamin deficiency of Schizochytrium sp.

Schizochytrium sp. is a heterotrophic microorganism capable of accumulating polyunsaturated fatty acids and has achieved industrial production of docosahexaenoic acid (DHA). It also has the potential for eicosapentaenoic acid (EPA) production. In this study, it was found that the cell growth, lipid synthesis and fatty acid composition of Schizochytrium sp. were significantly affected by the level of cobalamin in the medium, especially with regard to the content of EPA in the fatty acids. The content of EPA in the fatty acids increased 17.91 times, reaching 12.00%, but cell growth and lipid synthesis were significantly inhibited under cobalamin deficiency. The response mechanism for this phenomenon was revealed through combined lipidomic and transcriptomic analysis. Although cell growth was inhibited under cobalamin deficiency, the genes encoding key enzymes in central carbon metabolism were still up-regulated to provide precursors (Acetyl-CoA) and reducing power (NADPH) for the synthesis and accumulation of fatty acids. Moreover, the main lipid subclasses observed during cobalamin deficiency were glycerolipids (including glycerophospholipids), with EPA primarily distributed in them. The genes involved in the biosynthesis of these lipid subclasses were significantly up-regulated, such as the key enzymes in the Kennedy pathway for the synthesis of triglycerides. Thus, this study provided insights into the specific response of Schizochytrium sp. to cobalamin deficiency and identified a subset of new genes that can be engineered for modification.

Co-expression of metabolites and sensory attributes through weighted correlation network analysis to explore flavor-contributing factors in various Pyrus spp. Cultivars.

Flavor profiles of various Pyrus spp. cultivars exhibit significant variations, yet the underlying flavor-contributing factors remain elusive. In this investigation, a comprehensive approach encompassing metabolomics analysis, volatile fingerprint analysis, and descriptive sensory analysis was employed to elucidate the flavor disparities among Nanguoli, Korla fragrant pear, and Qiuyueli cultivars and uncover potential flavor contributor. The study comprehensively characterized the categories and concentrations of nonvolatile and volatile metabolites, and 925 metabolites were identified. Flavonoids and esters dominated the highest cumulative response, respectively. Utilizing weighted correlation network analysis (WGCNA), seven highly correlated modules were identified, yielding 407 pivotal metabolites. Further correlation analysis of the differential substances provided potential flavor constituents strongly associated with various sensory attributes; taste factors had a certain association with olfactory characteristics. Our findings demonstrated the manifestation of flavor was a result of the synergistic effect of various compounds; evaluation olfactory flavor necessitated a comprehensive consideration of taste substances.

Multicolor aptasensors for pesticide multiresidues detection in agricultural products using bioorthogonal surface-enhanced Raman scattering tags.

Realizing accurate pesticide multiresidue detection in a complex matrix is still a challenge for point-of-care sensing methods. Herein, we introduced background-free and multicolor aptasensors based on bioorthogonal surface-enhanced Raman scattering (SERS) tags and successfully applied them to analyze multiple pesticide residues. The excellent anti-interference and multiplex capability are due to the application of three bioorthogonal Raman reporters involving 4-ethenylbenzenamine (4-EBZM), Prussian blue (PB) and 2-amino-4-cyanopyridine (AMCP) with alkynyl and cyano groups, which demonstrated apparent Raman shift peaks at 1993 cm-1, 2160 cm-1, and 2264 cm-1 in the biologically Raman-silent region, respectively. Ultimately, a detection range of 1-50 nM for acetamiprid, atrazine and malathion was achieved with detection limits of 0.39, 0.57 and 0.16 nM, respectively. The developed aptasensors were successfully used to determine pesticide residues in real samples. These proposed multicolor aptasensors offer an effective strategy for pesticide multiresidue detection with advantages of anti-interference, high specificity and high sensitivity.

Development of a green fermentation strategy with resource cycle for the docosahexaenoic acid production by Schizochytrium sp.

The fermentation production of docosahexaenoic acid (DHA) is an industrial process with huge consumption of freshwater resource and nutrient, such as carbon sources and nitrogen sources. In this study, seawater and fermentation wastewater were introduced into the fermentation production of DHA, which could solve the problem of fermentation industry competing with humans for freshwater. In addition, a green fermentation strategy with pH control using waste ammonia, NaOH and citric acid as well as FW recycling was proposed. It could provide a stable external environment for cell growth and lipid synthesis while alleviating the dependence on organic nitrogen sources of Schizochytrium sp. It was proved that this strategy has good industrialization potential for DHA production, and the biomass, lipid and DHA yield reached to 195.8 g/L, 74.4 g/L and 46.4 g/L in 50 L bioreactor, respectively. This study provides a green and economic bioprocess technology for DHA production by Schizochytrium sp.

An interference-free SERS-based aptasensor for chlorpyrifos detection.

In this study, we propose an interference-free SERS-based aptasensor for trace detection of chlorpyrifos (CPF) in real samples. In the aptasensor, gold nanoparticles coated with Prussian blue (Au@PB NPs) were employed as SERS tags to provide a sole and intense Raman emission at 2160 cm-1, which could avoid overlapping with the Raman spectrum of the real samples in 600-1800 cm-1 to improve the anti-matrix effect ability of the aptasensor. Under the optimum conditions, this aptasensor displayed a linear response for CPF detection in the range of 0.1-316 ng mL-1 with a low detection limit of 0.066 ng mL-1. In addition, the prepared aptasensor shows excellent application to determine CPF in cucumber, pear and river water samples. The recovery rates were highly correlated with high-performance liquid chromatography‒mass spectrometry (HPLC‒MS/MS). This aptasensor shows interference-free, specific and sensitive detection for CPF and offers an effective strategy for other pesticide residue detection.

Determination and dynamics of ethylicin residues in cotton-field ecosystem.

In this work, we developed an efficient method to determine the ethylicin content in soil, cotton plant and cotton seed, and we also studied the fate of ethylicin in the cotton field ecosystem. The residual ethylicin was analyzed by GC-ECD. The limit of quantification was 0.005 mg/kg for soil, 0.01 mg/kg for the plant and cotton seed. The kinetics study of ethylicin residue showed that the ethylicin concentration in plant and soil can be regressively quantified as C = 1.0762e(-0.2529t) and C = 0.5535e(-0.1333t), representing a half-live of 2.7 and 5.2 days, respectively. As a conclusion, a dosage of 354 g a.i. ha(-1) was recommended, which could be considered as safe to human beings and animals.

The HOPS tethering complex is required to maintain signaling endosome identity and TORC1 activity.

The endomembrane system of eukaryotic cells is essential for cellular homeostasis during growth and proliferation. Previous work showed that a central regulator of growth, namely the target of rapamycin complex 1 (TORC1), binds both membranes of vacuoles and signaling endosomes (SEs) that are distinct from multivesicular bodies (MVBs). Interestingly, the endosomal TORC1, which binds membranes in part via the EGO complex, critically defines vacuole integrity. Here, we demonstrate that SEs form at a branch point of the biosynthetic and endocytic pathways toward the vacuole and depend on MVB biogenesis. Importantly, function of the HOPS tethering complex is essential to maintain the identity of SEs and proper endosomal and vacuolar TORC1 activities. In HOPS mutants, the EGO complex redistributed to the Golgi, which resulted in a partial mislocalization of TORC1. Our study uncovers that SE function requires a functional HOPS complex and MVBs, suggesting a tight link between trafficking and signaling along the endolysosomal pathway.

Enzyme-Linked Aptamer Kits for Rapid, Visual, and Sensitive Determination of Lactoferrin in Dairy Products.

Lactoferrin (Lf), as a popular nutritional fortification in dairy products, has the ability regulate the body's immune system and function as a broad-spectrum antibacterial, which is of great significance to the growth and development of infants and children. Herein, an indirect competitive enzyme-linked aptamer assay (ELAA) kit was established for rapid, sensitive, and visual determination of Lf in dairy products. In the construction, the Lf aptamer was conjugated with horseradish peroxidase (HRP) as the recognition probe and aptamer complementary strand (cDNA) were anchored onto the microplate as the capture probe. The recognition probes were first mixed with a sample solution and specifically bound with the contained Lf, then added into the microplate in which the free recognition probes in the mixture were captured by the capture probe. After washing, the remaining complex of cDNA/Aptamer/HRP in the microplate was conducted with a chromogenic reaction through HRP, efficiently catalyzing the substrate 3, 3', 5, 5'-tetramethylbenzidine (TMB), therefore the color shade would directly reflect Lf concentration. Under the optimization conditions, a good linear relationship (R2, 0.9901) was obtained in the wide range of 25-500 nM with the detection limit of 14.01 nM and a good specificity, as well as the reliable recoveries. Furthermore, the ELAA kits achieved the Lf determination with an accuracy of 79.71~116.99% in eleven samples, which consisted of three kinds of dairy products: including goat milk powder, cow milk powder, and nutrition drop. Moreover, the results were also validated by the high-performance capillary electrophoresis (HPCE) method. The ELAA kit provides a simple and convenient determination for Lf in dairy products, and it is highly expected to be commercialized.

Transcriptomic Analysis of Morphology Regulatory Mechanisms of Microparticles to Paraisaria dubia in Submerged Fermentation.

Liquid submerged fermentation is an effective strategy to achieve large-scale production of active ingredients by macrofungi, and controlling mycelium morphology is a key factor restricting the development of this technology. Mining for superior morphological regulatory factors and elucidation of their regulatory mechanisms are vital for the further development of macrofungal fermentation technology. In this study, microparticles were used to control the morphology of Paraisaria dubia (P. dubia) in submerged fermentation, and the underlying regulatory mechanisms were revealed by transcriptomic. The relative frequency of S-type pellet diameter increased significantly from 7.14 to 88.31%, and biomass increased 1.54 times when 15 g/L talc was added. Transcriptome analysis showed that the morphological regulation of filamentous fungi was a complex biological process, which involved signal transduction, mycelium polar growth, cell wall synthesis and cell division, etc. It also showed a positive impact on the basic and secondary metabolism of P. dubia. We provided a theoretical basis for controlling the mycelium morphology of P. dubia in submerged fermentation, which will promote the development of macrofungal fermentation technology.

Strategy of Dimercaptothiol as Self-assembled Monolayers Enhance the Sensitivity of SPR Immunosensor for Detection of Salbutamol.

The formation of self-assembled monolayers (SAMs) is a normal method for the immobilization of biorecognition elements immobilized on SPR sensors. With this method, mercaptopropionic acid (MPA) with carboxylic and thiol group is the most commonly used. Dimercaptosuccinic acid (DMSA) having two carboxylics and two thiol groups is a classical antidote for heavy metal ions. In this paper, DMSA was first used to form SAMs to connect the antigen on the chip of a surface plasmon resonance (SPR) immunosensor for detection of salbutamol (SAL), and the results were compared with a traditional (MPA)-SPR sensor. Dihydrolipoic acid(DHLA)-SPR showed that the recognition efficiency of antigen and antibody of DMSA-SPR immunosensor was 170.1% at room temperature with the linear range of 5 - 150 ng/mL. The recovery rate of this sensor applied to SAL detection in pork reached 94.9 - 108.0% and the limit of quantification (LOQ) was 5 ng/mL. The results were in good correlation with the analysis results of ultra-high phase liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis. This novel DMSA-SPR immunosensor provides insight into a new idea and method for improving the sensitivity of SPR immunosensors and can be widely used in the detection of other small molecules.

Advances in Surface-Enhanced Raman Scattering-Based Aptasensors for Food Safety Detection.

Owing to the excellent performances of high sensitivity, high specificity, on-site detection, and multiplexing capability, surface-enhanced Raman scattering (SERS)-based aptasensors have performed prosperous applications and gained impressive progress in food safety. Herein, we reviewed the SERS-based aptasensors from the principles to specific applications in food safety. First, the sensor-working principles, SERS label design and preparation are introduced. Then, the popular platforms in the aptasensors are summarized with their advantages and disadvantages, followed by their representative applications. Further, the specific applications of developing SERS-based aptasensors in food safety are systematically provided. Moreover, the multiplex analysis using SERS labels are highlighted. Finally, challenges and perspectives for improving the SERS-based aptasensor performance are also discussed, aiming to give some proposes for researchers to choose suitable SERS-based aptasensors according to specific applications.

TORC1 Determines Fab1 Lipid Kinase Function at Signaling Endosomes and Vacuoles.

Organelles of the endomembrane system maintain their identity and integrity during growth or stress conditions by homeostatic mechanisms that regulate membrane flux and biogenesis. At lysosomes and endosomes, the Fab1 lipid kinase complex and the nutrient-regulated target of rapamycin complex 1 (TORC1) control the integrity of the endolysosomal homeostasis and cellular metabolism. Both complexes are functionally connected as Fab1-dependent generation of PI(3,5)P2 supports TORC1 activity. Here, we identify Fab1 as a target of TORC1 on signaling endosomes, which are distinct from multivesicular bodies, and provide mechanistic insight into their crosstalk. Accordingly, TORC1 can phosphorylate Fab1 proximal to its PI3P-interacting FYVE domain, which causes Fab1 to shift to signaling endosomes, where it generates PI(3,5)P2. This, in turn, regulates (1) vacuole morphology, (2) recruitment of TORC1 and the TORC1-regulatory Rag GTPase-containing EGO complex to signaling endosomes, and (3) TORC1 activity. Thus, our study unravels a regulatory feedback loop between TORC1 and the Fab1 complex that controls signaling at endolysosomes.