Abstract:During the fermentation of plant-based fermented food, cyanogenic glycosides from plants can be converted into cyanide, which will cause adverse effects. Therefore, it is of great significance to analyze the generation and control strategies of cyanide in plant-based fermented food. The accumulation of cyanide can be controlled by the degradation of cyanide precursors and the enzymatic degradation of cyanide. The author reviews the sources and control strategies of cyanide in plant-based fermented food and proposes new strategies for controlling cyanide in plant-based fermented food, aiming to provide references for the research on cyanide control in fermented food.

Abstract:Organic sulfur compounds are often potent odorants, being key flavor components of plant-based foods and bioactive compounds with pro-health functions. In many vegetables and fruits, especially Brassica and Allium vegetables, sulfur compounds determine their specific flavors. Main groups of sulfur compounds in plants include sulfides, polysulfides, isothiocyanates (ITCs), nitriles, epithethriles, thiols, thiosulfinates, as well as heterocyclic sulfur compounds found in shiitake or truffle. The author summarized the roles of major organic sulfur compounds in flavors of plants, reviewed the recent progress in metabolism and transformation of these organic sulfur compounds under various processing conditions, and made an outlook on the future research directions of organic sulfur compounds.

Abstract:Excessive consumption of sugars poses numerous health risks to humans and can induce diabetes, obesity, and dental caries. Sugar reduction has become a global initiative, prompting the research and development of low-calorie natural sweeteners. The advancements in the attributes, production techniques, metabolism, and functions of six representative natural sweeteners, namely D-allulose, D-tagatose, erythritol, xylitol, steviol glycosides, and mogroside, and their practical applications were reviewed. The potential development directions of the sweetener industry were discussed. The aims are to ensure accurate awareness and proper utilization of natural sweeteners by both food developers and consumers and to provide guiding significance for future research and market expansion of natural sweeteners.

Abstract:As key biocatalysts, lipases play essential roles in catalyzing the hydrolysis of triglycerides and the esterification of fatty acids. Therefore, accurate measurement of lipases enzyme activity is crucial. Traditional methods, such as plate assay and titration, indirectly assess lipase enzyme activity by measuring the fatty acids produced from the substrate catalyzed by lipases. Methods like the copper-soap colorimetric assay, p-nitrophenol assay, and probe colorimetric assay determine lipase enzyme activity based on changes in the color of the reaction products. Recently developed methods, such as liquid foam detection, are limited to qualitative analysis, whereas the fluorescence probe and biosensor-based detection methods offer higher sensitivity, making them more suitable for measuring lipase enzyme activity in complex media. The author provides a brief overview of the principles, limitations applicable conditions, and current developments of various lipase enzyme activity detection methods, along with a comprehensive comparison and summary, aiming to offer a reference for future research on lipase enzyme activity detection.

Abstract:[Objective] D-pantothenic acid (vitamin B₅) is a water-soluble vitamin widely used in feed, food, chemical, pharmaceutical and other industries. At present, vitamin B₅ is mainly produced by chemical-enzymatic methods, while this production process generates a large amount of cyanide-containing wastewater. Cell factories have the characteristics of being green and environmentally friendly. Therefore, it is necessary to develop a biotransformation system for producing D-pantothenic acid with low value substrates. [Method] With the β-alanine synthesis strain constructed in the previous study as the starting strain, a three-enzyme system was constructed by coupling L-aspartase from Corynebacterium glutamicum and pantothenate synthase (PanC) from Bacillus subtilis. The D-pantothenic acid biosynthesis pathway was validated and optimized in vitro and then reconstructed in cells. By optimizing the ratio of three enzymes and introducing an ATP cycle system, the system optimization and large-scale production of D-pantothenic acid were finally achieved in a 5 L bioreactor. [Result] Under the optimal biotransformation conditions, 70 g/L of fumaric acid and 89 g/L of D-pantolactone were converted to 128.6 g/L of D-pantothenic acid through whole cell catalysis, with a molar conversion rate of 97.3%. [Conclusion] An effective biotransformation system for producing D-pantothenic acid from fumaric acid and D-pantolactone is successfully developed.

Abstract:[Objective] Nobiletin (NOB), an important polymethoxy-flavonoid in citrus peel, has a variety of biological activities and health-promoting effects. However, it has poor water solubility and it is prone to crystallization. Nano-emulsion delivery systems have been widely used to improve the bioavailability of lipophilic components. The effects of these systems on the bioavailability and biotransformation of NOB are studied, with the aim of providing guidance for improving the bioavailability and health-promoting effects of citrus flavonoids including NOB and promoting the application of NOB in functional food. [Method] A NOB-encapsulated nano-emulsion delivery system was established. Feces of mice were collected for the identification of metabolites, and then the pharmacokinetics and in vivo distribution of NOB were analyzed. [Result] Six metabolites were identified from mouse feces, among which NOB, 4’-demethylnobiletin, 3’-demethylnobiletin, and 3’,4’-didemethylnobiletin were the main metabolites. Pharmacokinetic analysis showed that the nano-emulsion significantly improved the bioavailability of NOB, increasing the blood mass concentration and prolonging the action time. The area under the curve (AUC_t) and the maximum blood mass concentration (C_max) of NOB in the nano-emulsion were 5.8~14.4 and 1.9~3.6 times that of unencapsulated NOB. Moreover, the nano-emulsion system prolonged the half-life of NOB by 2.5~4.9 times. The in vivo distribution analysis of metabolites showed that the concentrations of metabolites in the liver were very low. [Conclusion] The NOB encapsulated in the nano-emulsion delivery system can enter the serum through lymphatic circulation, which avoids the liver first pass effect and may explain the improving effects of the nano-emulsion delivery system on the bioavailability of NOB. Metabolites mainly exist in the form of conjugation in the small intestine, while they are hydrolyzed into the free form by the gut microbiota in the cecum and colon.

Abstract:[Objective] This study aimed to evaluate the genetic stability of Lactobacillus casei Zhang (LCZ) during continuous passaging. [Method] LCZ was continuously cultured for 100 generations in MRS liquid medium, with samples collected at generations 0, 25, 50, 75, and 100. The morphology, carbohydrate utilization, and genomic changes of LCZ were analyzed. [Result] No significant differences were observed in the morphology and carbohydrate utilization of LCZ across generations 0, 25, 50, 75, and 100. The genome size and GC proportion showed no significant differences compared to the original genome. SNP mutation analysis indicated that the LCZ genome was highly conserved across generations, with a low mutation frequency. Average nucleotide identity (ANI) and phylogenetic tree analyses revealed that the LCZ strains from different generations were closely related to the original genome. No significant differences were found in the annotations of the carbohydrate-active enzyme (CAZymes) among different generations, suggesting consistent carbohydrate utilization ability. [Conclusion] LCZ exhibited high genetic stability during continuous passaging.

Abstract:[Objective] To determine the effects of glass transition temperature(T_g) and collapse temperature(T_c) of protectants on the freeze-drying survival rate of Lactobacillus plantarum(L. plantarum). [Method] The T_g and T_c of protectants, such as 10% sucrose, 10% sorbitol, and PBS buffer, were measured by differential scanning calorimetry (DSC) and freeze-drying microscopy (FDM). [Result] The relationship of the freeze-drying survival rate of strains with the T_g and T_c of different protectants showed that there was a close relationship of the freeze-drying survival rate of strains with the T_g and T_c of the protectant suspension. Compared to sorbitol and PBS groups, the T_g of sucrose group increased by 7.2 and 7.7 ℃, respectively, while T_c increased by 8.0 and 8.8 ℃, respectively. The freeze-drying survival rate of the sucrose group was the highest, showing improvements of 49.2% and 54.6% over the sorbitol and PBS groups, respectively. Furthermore, a high T_g polysaccharide composite protectant was developed. The T_g and T_c of the optimal composite protectant increased by 4.6 ℃ and 4.4 ℃ compared to those of a single sucrose protectant, and the freeze-drying survival rate was 28.2% higher than that of a single sucrose protectant. [Conclusion] The results showed that the T_g and T_c of different protectants were very different. As the T_g and T_c became higher, the freeze-drying survival rate was higher. Based on T_g, a highly efficient composite protectant was developed, which was beneficial in improving the freeze-drying survival rate of Lactobacillus plantarum.

Abstract:[Objective] This study aimed to screen out a microbial strain capable of degrading aflatoxin B₁ (AFB₁) and decipher the degradation mechanism. [Method] With coumarin as the sole carbon source, AFB₁-degrading strains were isolated and screened from the larval gut of Monochamus alternatus (Coleoptera: Cerambycidae), and the degradation mechanism for AFB₁ was investigated. [Result] After primary screening and re-screening, a strain with the degradation rate reaching 94.71% for AFB₁ was obtained, and this strain was identified as Bacillus siamensis (B. siamensis) DY3123. The results of experiments on the degradation of AFB₁ by different cellular components indicated that the main active substances responsible for degrading AFB₁ were from the cell-free culture supernatant of B. siamensis DY3123, which showed the optimum degradation performance at 80 ℃ and pH 8.0 after 36 h. Cu²⁺ improved the degradation activity of the cell-free supernatant, while Zn²⁺, Mg²⁺, and Fe³⁺ exerted inhibitory effects. In addition, the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (methyl thiazolyl tetrazolium, MTT) assay was employed to examine the effects of the degradation products on the viability of lymphocytes, which indicated that the degradation products had no significant impact on cell viability. [Conclusion] The findings lay a foundation for the application of B. siamensis DY3123 in the food and animal feed industry.

Abstract:[Objective] This study aimed to investigate the protective effect of selenium-enriched peptide of Cardamine violifolia (SPE) on the alcohol-induced oxidative stress damage in the liver of mice. [Method] A mouse model of alcoholic liver damage was established by gradient alcohol gavage. The effects of SPE on the serum levels of biochemical indicators, liver oxidative stress indicators, liver histopathology and liver metabolic profile in mice were studied. [Result] SPE significantly alleviated alcohol-induced liver damage and elevated the levels of antioxidant enzymes in the liver. Metabolomics results showed that SPE significantly recovered the levels of 37 metabolites in the liver of mice. These metabolites were involved in metabolic pathways such as biosynthesis of unsaturated fatty acids, linoleic acid metabolism, and glycerophospholipid metabolism. [Conclusion] SPE exerts a positive protective effect on alcohol-induced oxidative stress injury in mouse liver by regulating the activation of linoleic acid metabolism, biosynthesis of unsaturated fatty acids, and glycerophospholipid metabolism.

Abstract:[Objective] To explore the structural characteristics and biological functions of polysaccharides extracted from Patinopecten yessoensis skirt by twice enzymatic hydrolysis and alcohol precipitation. [Method] High performance liquid chromatography, ultraviolet spectroscopy, and Fourier transform infrared spectroscopy were employed to characterize the structure of polysaccharides extracted from Patinopecten yessoensis skirt, and the antioxidant activity and immunomodulatory activity of the extracted polysaccharides were determined. Furthermore, animal experiments were carried out to examine the effects of the extracted polysaccharides on gut microbiota and colonic immunoglobins in mice. [Result] The polysaccharides extracted from Patinopecten yessoensis skirt were composed of five monosaccharides, with an average molecular weight of 2.538×10⁵. The polysaccharides had a D type pyran ring structure with α?-glycosidic bond and no uronic acid. The extracted polysaccharides showed weak antioxidant activity, with the 1,1-diphenyl-2-picrylhydrazyl （DPPH） and hydroxyl free radical scavenging rates only 19.7% and 20.1% those of vitamin C (positive control), respectively. The extracted polysaccharides promoted macrophages to secrete cytokines and nitric oxide (NO). At the mass concentration of 200 μg/mL, the extracted polysaccharides increased the mass concentrations of tumor necrosis factor-α （TNF-α）, and interleukin-1β （IL-1β）, and the concentration of NO by 75.7%, 22.8%, and 46.6%, respectively. In addition, the polysaccharides improved the gut microbiota structure in mice by significantly increasing the relative abundance of probiotic genera (Bifidobacterium and Bacteroides). The mass concentrations of immunoglobin A, immunoglobin G, and immunoglobin M in the colon tissue of mice fed with a high dose of the extracted polysaccharides increased by 13.6%, 68.7%, and 23.9%, respectively. [Conclusion] The polysaccharides from Patinopecten yessoensis skirt promoted the proliferation of probiotics and regulated the immunity. The findings provide a theoretical basis for the further development and utilization of polysaccharides from Patinopecten yessoensis skirt.

Abstract:[Objective] This study aims to investigate the in vivo and in vitro antioxidant activities of Agaricus bitorquis (Quél.) Sacc. polysaccharides, including polysaccharides from sporocarp (PS), intracellular polysaccharides (IPS), and exopolysaccharides (EPS). [Method] Five in vitro antioxidant indexes and four in vivo antioxidant indexes were determined using an in vitro antioxidant system and an in vivo antioxidant (mice injured by hypoxia oxidation) model. [Result] The results showed that IPS, EPS, and PS all had scavenging abilities against DPPH radical, ABTS radical, hydroxyl radical, and superoxide anion radical but at significantly different levels (P<0.05), and the effect of IPS was the best. IPS, EPS, and PS could decrease the concentration of malondialdehyde (MDA) and increase the activities of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) in the blood of mice injured by hypoxia oxidation, and the levels changed by the three kinds of polysaccharides were significantly different (P<0.05). Compared with the blank group, IPS could decrease the concentration of MDA by 73.00% and increase the activity of CAT by 28.93%. The activities of SOD and GSH-Px were increased by 25.08% and 72.14%, respectively by PS. [Conclusion] All the three kinds of polysaccharides from Agaricus bitorquis (Quél.) Sacc. have strong antioxidant activity in vivo and in vitro, with IPS having the highest antioxidant activity, which has high research value as a natural antioxidant.

Abstract:[Objective] This study aimed to explore the components in the exudates from threshing and redrying tobacco leaves and their effects on human vascular endothelial (EA.hy926) cell damage. [Method] The EA.hy926 cell model of cytotoxic damage was established with the exudates from threshing and redrying tobacco leaves. After pretreatment with VC, the methyl thiazolyl tetrazolium (MTT) method was employed to evaluate the viability of EA.hy926 cells, and the relative content of reactive oxygen species (ROS) in EA.hy926 cells was determined. [Result] Obvious cell damage was observed after 24 h of stimulation with the exudates from threshing and redrying tobacco leaves, which indicated the cell model of cytotoxic damage was successfully established. VC pretreatment significantly reversed the above changes. [Conclusion] VC exerts obvious protective effect on the cytotoxic damage of EA.hy926 cells that is induced by the exudates from threshing and redrying tobacco leaves by reducing the ROS level.

Abstract:[Objective] According to the principle of specific binding of nickel-chelated agarose affinity chromatography medium (Ni-NTA) to histidine (His)-tagged proteins, the histidine-tagged Escherichia coli (E. coli)-derived pyridoxine kinase (EcpdxK) was immobilized with the Ni-NTA to form an immobilized reactor, and the optimal reaction conditions for the conversion of pyridoxine (PN) to pyridoxine phosphate (PNP) were investigated. [Method] The effects of temperature, pH, metal ion concentration, and recycling times on this catalytic reaction were investigated by one-way analysis of variance. [Result] The optimal reaction conditions of the immobilized EcpdxK were 55 ℃, pH 5.0, and 30 mmol/L Mg²⁺, under which the immobilized EcpdxK was able to convert 99% of PN into PNP within 10 min. In the immobilized EcpdxK-packed bed reactor, the column retention time of the EcpdxK reaction liquid was 10 min, and the conversion efficiency was still as high as 93% after 12 h of continuous reaction. [Conclusion] The immobilized EcpdxK has good temperature tolerance, pH tolerance, and operational stability, and the immobilized EcpdxK-catalyzed synthesis of PNP is a simple and cost-effective process with the potential for industrial application.

Abstract:[Objective] This study aimed to explore the regulatory effects of xanthan gum (XG) on the properties of egg white protein foam-type gel.[Method] The changes of browning intensity, color, textural properties, rheological properties, molecular conformation, and microstructure of the egg white protein foam-type gel supplemented with xanthan gum were determined. [Result] With the increase in mass fraction of xanthan gum, the a^* value and browning intensity of the egg white protein foam-type gel increased significantly, while the L^* value and b^* value decreased significantly. When the mass fraction of xanthan gum was 1.2%, the hardness, resilience, and chewiness of the egg white protein foam-type gel reached the maximum values, which were 109.18 g, 0.16, and 49.04 g, respectively. The addition of xanthan gum significantly increased the elastic modulus (G') and energy storage modulus (G") of the egg white protein foam-type gel, and enhanced the stability and strength of the gel network structure. The molar concentrations of total sulfhydryl group and disulfide bond and the endogenous fluorescence intensity decreased significantly, while the molar concentration of free sulfhydryl group increased significantly. When the mass fraction of xanthan gum was 0.6%~1.2%, the egg white protein foam-type gel formed a smaller and denser network microstructure. [Conclusion] Adding an appropriate amount of xanthan gum can effectively improve the properties and structure of the egg white protein foam-type gel. The findings provide a theoretical basis for innovative research on the processing characteristics of egg white gels.

Abstract:[Objective] This study aims to develop a method for the rapid detection of norovirus GⅡ based on loop-mediated isothermal amplification (LAMP). [Method] Four primers were designed based on the conserved region of norovirus and the reaction system and conditions were optimized. [Result] The optimal reaction system was composed of 0.32 U/μL Bst DNA polymerase, 10 mmol/L MgSO₄, 1.2 mmol/L dNTP, 1.6 μmol/L BIP, 1.6 μmol/L FIP, 0.4 μmol/L F3, and 0.4 μmol/L B3. The optimal reaction conditions were reaction at 63 ℃ for 50 min and then at 85 ℃ for 5 min. The established LAMP method specifically recognized norovirus GⅡ, with the sensitivity of 1×10^-7 ng/μL, which was better than that of conventional PCR. In addition, three visualization dyes were screened. The results showed that SYBR Green I, phenol red, and hydroxynaphthol blue (HNB) demonstrated significant color contrast between positive and negative results, indicating that all the three dyes could be used for visualization. [Conclusion] A fast, specific, and simple method is successfully established for detecting norovirus GⅡ and applied to the detection of aquatic products.

Abstract:[Objective] This study aims to achieve rapid quantitative detection of beef- and duck-derived ingredients in meat products. [Method] The DNA extraction-free method was combined with fluorescent quantitative PCR (qPCR) lyophilized reagents was developed. The DNA extraction-free method was employed to prepare the template for qPCR. The premixed qPCR reagents were prepared by lyophilization. A portable qPCR system was used for amplification with the lyophilized reagents. [Result] The DNA extraction-free method with simplified sample extraction and purification steps achieved the detection within 10 min. The method combining the DNA extraction-free DNA method and qPCR lyophilized reagents can produce results within 45 min, with the limit of detection being 1 pg/μL. The premixed qPCR lyophilized reagents can be stored at 4 ℃ for 6 months, at room temperature for 4 months, and at 37 ℃ for 14 d. [Conclusion] The qPCR lyophilized reagents are appropriate for a portable qPCR system and can thus achieve rapid identification of adulteration in meat products.

Abstract: [Objective] To establish a method for quantifying 14 human milk oligosaccharides based on ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry. [Method] The supernatant obtained by centrifugation of defatted human milk was loaded on an Waters ACQUITY UPLC^? BEH Amide column (2.1 mm×100 mm×1.7 μm) for gradient elution, with 25 mmol/L ammonium acetate solution and acetonitrile as mobile phases. Data of human milk oligosaccharides were collected by parallel reaction monitoring in the positive ion mode. Quantitative analysis was performed with the external standard method. [Result] The calibration curves of 14 human milk oligosaccharides were linear within the mass concentration range of 0.10~100.00 μg/mL, with the correlation coefficient≥0.980 2. The limits of detection and limits of quantitation were 0.05~1.00 μg/mL and 0.10~5.00 μg/mL, respectively. The recovery of each oligosaccharide added to human milk ranged from 78.03% to 105.23%, with the relative standard deviations ranging from 0.14% to 5.86%. [Conclusion] The results showed that this method could rapidly and effectively detect human milk oligosaccharides in the samples from different sources, providing technical support for the research on human milk oligosaccharides.

Abstract:[Objective] A detection method for viable Listeria monocytogenes (LM) was established combining improved propidium monoazide (PMAxx) with droplet digital PCR (ddPCR). [Method] After optimization of the final PMAxx concentration, dark treatment time, and exposure time, the optimal PMAxx-ddPCR detection system was established. Different volume ratios of viable LM were employed to verify the accuracy of the PMAxx-ddPCR method, and the specificity, sensitivity, and reproducibility of this method were examined. Cheese stick samples were artificially contaminated with different concentrations of viable and dead LM and then used to compare the detection results of the conventional plate counting method and the PMAxx-ddPCR method established in this study. Additionally, commercially available enoki mushrooms and ham sausages were tested to evaluate the practical detection performance of the PMAxx-ddPCR method. [Result] At a final PMAxx concentration of 10 μmol/L, dark treatment time of 10 min, and exposure time of 10 min, PMAxx significantly inhibited the DNA amplification of dead bacteria, while having no significant effect on that of viable bacteria. The developed PMAxx-ddPCR method only generated specific amplification for LM, with a limit of quantification of 147 CFU/mL. The relative standard deviations (RSD) of the method were consistently less than 20%, indicating good repeatability. In the artificial contamination experiment of cheese sticks, the quantification results of LM by the plate counting method and the PMAxx-ddPCR method had no significant difference (P>0.05). Further detection of 17 enoki mushroom samples and 16 ham sausage samples revealed that LM was detected in 7 enoki mushroom samples by both PMAxx-ddPCR and plate counting methods. Moreover, the quantitative results of the two methods showed no significant difference (P>0.05). [Conclusion] A PMAxx-ddPCR method is established for detecting viable LM, enabling specific quantitative detection of viable LM in food.