The combination of the traditional culture-dependent method and high-throughput sequencing was used to investigate the level of microbial contamination on the surface of pig carcasses during the slaughter and segmentation process. Meanwhile, the number of microbial colonies on the slaughter knives and the contact surfaces of the segmentation workshop were counted to identify the key pollution links in the slaughter and segmentation process. The results showed that a total of 881458 valid sequences and 864 operational taxonomic units (OTUs) were obtained by sequencing. The samples were annotated to 22 phyla, 33 classes, 79 orders, 162 families, 382 genera and 613 species of microorganisms. Proteobacteria, Bacteroidota and Firmicutes were the dominant bacterial phyla. Acinetobacter and Aeromonas were the major dominant bacterial genus. The bacterial community diversity during the slaughter and segmentation process was in decreasing order as follows: bleeding > dehairing > segmentation > evisceration > final wash > chilling. The microbial diversity on the carcass surface was the lowest in the chilling stage, and increased after segmentation, indicating that the segmentation stage was the key contamination link. The results of traditional microbial counting were consistent with the results of sequencing. From dehairing to chilling, the number of each bacterial group on the surface of pig carcasses was decreased, but increased significantly after segmentation. The total number of bacterial colonies on the carcass surfaces in the segmentation workshop was 6.11 (lg(CFU/cm²)) on average, which was higher than that on the slaughter knives (4.86 (lg(CFU/cm²)) on average), indicating that the contact surfaces of the segmentation workshop were the key pollution source, and so the segmentation link was the key pollution link.

Synbiotics refer to biological agents (probiotics) used in combination with probiotics. In recent years, accumulating studies have reported that synbiotics possess many health benefits. The efficacy of symbiotics is affected by the selection of probiotics and prebiotics. Fructooligosaccharides and inulin are commonly used as probiotics, which can be selectively absorbed by probiotics in the intestine and promote the proliferation of probiotics, thereby keeping the host healthy. This paper reviews the differential metabolism and metabolism pathways of fructooligosaccharides (FOS) and inulin by lactic acid bacteria, and summarizes the mechanisms of action of the hydrolases, transport systems, and regulatory proteins at the molecular level in order to provide basis for understanding the regulatory mechanism of the metabolic network of FOS and inulin by lactic acid bacteria. Besides, it summarizes the recent applications of synbiotics containing FOS and/or inulin with a view to providing valuable evidence to extend the combined application of prebiotics and probiotics.

Pyrethroid pesticides are widely used in agricultural production due to their stability and high effectivity. The problem of pyrethroid residues in agricultural products has become increasingly prominent, posing a threat to food safety. The problem of pesticide residues has attracted growing attention from consumers and researchers. Therefore, it is urgent to understand the pollution status of pyrethroid pesticides in agricultural products and seek effective measures to control it. This article introduces the characteristics of pyrethroid pesticides and describes the current status of pyrethroid pesticide residues in agricultural products globally. Besides, it summarizes the technologies for the removal of pyrethroid pesticides and outlines future prospects for the development of new technologies in this field. We expect that this article will provide a reference for reducing pyrethroid pesticide residues in agricultural products and ensuring the safety of agricultural products.

China is a big producer and consumer of grains and oils. The development of high-yield grains is closely related to chemicals such as pesticides. With the improvement of people’s living standards, residents’ requirements for foods have changed from ‘security of output’ to ‘equal emphasis on quality and output’. In order to strengthen the management of grain quality and safety, it is urgent to comprehensively understand the status of pesticide pollution in grains and develop more efficient, convenient and rapid detection technologies. This paper briefly summarizes the characteristics of pesticides and pesticide residues, analyzes the current status of the use and residues of pesticides in raw materials for grains and oils in China, reviews the existing rapid detection methods and technologies for pesticide residues in grains, and compares the advantages and disadvantages of various rapid detection methods and products. This review is expected to provide a reference for quality inspection during grain purchase.

Pyrethroids (PYRs) are widely used as pesticides due to low toxicity and high efficacy; however, PYRs residues have caused increasingly serious environmental and food safety problems. 3-Phenoxybenzoic acid (3-PBA), one of the major intermediate degradation products of PYRs, is more stable and toxic than the parent pesticides, and its residue can further aggravate environmental and agricultural product pollution. In recent years, filamentous fungal degradation of PYRs and 3-PBA has been reported, and research on this topic mainly focuses on strain screening, degradation characteristics, degradation pathways and localization of degradation enzymes. Unfortunately, key enzymes and their encoding genes involved in the degradation process are rarely reported. With the development of sequencing technology, molecular biology technology has provided a new strategy to mine PYR-degrading enzymes and their encoding genes in filamentous fungi. In this article, the basic properties, residues status and hazards of PYRs and 3-PBA are described. The filamentous fungi capable of degrading PYRs and 3-PBA, and their degradation pathways and degrading enzymes are reviewed. In addition, future prospects for the development of methods for screening and verification of degrading enzymes and their encoding genes are discussed. We expect that this review will provide a theoretical basis for understanding the degradation pathways and mechanisms of PYRs and 3-PBA by filamentous fungi and provide a reference for reducing residual pesticides in the environment and agricultural products.

The use of organochlorine and organophosphorus pesticides has been prohibited due to their highly toxicity. In recent years, pyrethroids (PYRs) have been widely used in agricultural production and the environment due to their high efficiency and stability, but the residual hazards caused by their frequent use have become increasingly prominent. 3-Phenoxybenzoic acid (3-PBA) is one of the major metabolites of PYRs, which is an environmental estrogen with great potential harms. Pesticide residues have seriously affected people’s production and life, which has attracted extensive attention from researchers. PYRs and 3-PBA degrading bacteria have been widely reported, and microbial and enzymatic degradation is recognized as an effective method for reducing or removing pesticide residues from agricultural products and the environment. The continuous development of genetic engineering and molecular biology technology provides a new way to explore methods for reducing pesticide residues. In this article, we summarize the basic properties and residual hazards of PYRs and 3-PBA, and we review the current status of PYRs residues in agricultural products and the environment as well as recent progress in research on the modes of microbial metabolism and the mechanisms of microbial adsorption and degradation of PYRs. Moreover, we give an outlook on enzymes degrading PYRs and their genetic engineering in order to provide a reference for solving the problem of pesticide residues in agricultural products and the environment.

As a biocatalyst, phenolic acid decarboxylase catalyzes the decarboxylation of its substates into 4-vinyl derivatives, which exhibit numerous advantages and holds promising prospects. In this study, phenolic acid decarboxylase from Bacillus subtilis J6 (BJ6PAD) was engineered by C-terminal substitution to obtain mutants with enhanced catalytic capacity. Homology modeling, molecular docking, and molecular dynamics simulation were employed to analyze the interactions between the enzyme and its substrates. The results indicated that C-terminal substitution affected the enzyme’s substrate affinity and catalytic efficiency. The constructed mutants, BJ6PAD-C1 and BJ6PAD-C2, exhibited significantly improved catalytic activity towards most phenolic acid substrates, particularly caffeic acid, towards which their activities increased by 20.34% and 29.97% when compared with that of the wild-type enzyme. Moreover, both mutants showed increased affinity for ferulic acid, caffeic acid, and sinapic acid. Specifically, the catalytic efficiency of BJ6PAD-C1 increased by 4%, 24%, and 145% for these three phenolic acids, respectively, and that of BJ6PAD-C2 by 7%, 37%, and 114%, respectively. Finally, molecular docking analysis predicted the key binding sites of the substrates, revealing that C-terminal substitution modulated the interactions between the key amino acid residues in the substrate-binding cavity. Molecular dynamics simulation was performed to elucidate the reasons for the altered catalytic activity from two perspectives: protein structure and energy differences, suggesting that the mutations might widen the protein import channel, facilitating easier ligand access to the substrate-binding pocket. Meanwhile, structural changes in the enzyme could lead to off-target effects of substrates, thereby reducing its catalytic activity. This study not only enriches PAD resources but also offers new insights into the relationship between the structure and function of PAD.

In this study, a gas-producing strain of Acetilactobacillus jinshanensis was isolated from spoiled vinegar. After heat treatment at different temperatures, it was found that this strain was a heat-intolerant one, which could be inactivated at 60 ℃ for 10 min. The effect of A. jinshanensis on the quality of vinegar was studied. The results showed that the total acid, amino acid nitrogen, soluble solids, and sediment contents of vinegar increased significantly, while the reduced sugar content decreased significantly after vinegar quality deterioration caused by A. jinshanensis (P < 0.05). In addition, the total organic acid content increased; the contents of lactic, oxalic, and malic acid increased significantly, the contents of citric and tartaric acid decreased significantly (P < 0.05), while the contents of acetic and succinic acid did not significantly change (P > 0.05). The content of total volatile flavor substances decreased by approximately 50%, with the dominant ones being esters and aldehydes. Based on odor activity value (OAV), it was found that the contents of the main characteristic flavor substances such as 3-hydroxy-2-butanone, 2,3,5,6-tetramethylpyrazine, ethyl acetate, phenethyl acetate decreased after vinegar quality deterioration, and the contents of furfuryl alcohol and isovaleric acid increased, resulting in a bland taste or even off-flavor in vinegar, which was in line with the results of sensory evaluation. Furthermore, low-temperature (60 ℃) heat treatment did not have a significant effect on physicochemical indexes or organic acids, but had a significant impact on the flavor of vinegar (P > 0.05). The heat treatment increased the contents of characteristic flavor substances such as phenylethyl acetate, 3-hydroxy-2-butanone, phenethyl alcohol, and reduced the content of isovaleric acid in spoiled vinegar, thereby improving its flavor. To sum up, contamination with A. jinshanensis has a great impact on the flavor of vinegar, which can be improved by heat treatment to a certain extent.

Phenolic acid decarboxylase (PAD) (lyase, EC 4.1.1.102) catalyzes the conversion of phenolic acids such as coumaric acid, ferulic acid, caffeic acid, and glucosic acid that are widely distributed in plants into 4-vinyl derivatives. 4-Vinyl derivatives are not only high-grade fragrances, but also key precursors for the synthesis of other spices such as vanillin. Food spices are mainly chemically synthesized in the current market. By contrast, the biosynthesis method, which is characterized by single precursor substances, mild conditions and environmental friendliness, has broad application prospects, and biosynthesized spices are regarded as being equivalent to natural products. Therefore, using PAD for the biosynthesis of 4-vinyl derivatives is of great significance to supplementing the production pathway of this type of fragrance. In this article, PAD derived from microorganisms are summarized from five aspects: origins, molecular structure, catalytic mechanism and structure-function correlation, catalytic properties, and techniques to improve the catalytic efficiency.