Controlling release of astaxanthin in ß-sitosterol oleogel-based emulsions via different self-assembled mechanisms and composition of the oleogelators.

In this study, three types of ß-sitosterol-based oleogels (ß-sitosterol + Î³-oryzanol oleogels, ß-sitosterol + lecithin, oleogels and ß-sitosterol + monostearate oleogels), loaded with astaxanthin, were employed as the oil phase to create oleogel-based emulsions (SO, SL, and SM) using high-pressure homogenization. The microstructure revealed that fine-scale crystals were dispersed within the oil phase of the droplets in the ß-sitosterol oleogel-based emulsion. The bioaccessibility of astaxanthin was found to be 58.13 %, 51.24 %, 36.57 %, and 45.72 % for SM, SL, SO, and the control group, respectively. Interestingly, the release of fatty acids was positively correlated with the availability of astaxanthin (P = 0.981). Further analysis of FFAs release and kinetics indicated that the structural strength of the oil-phase in the emulsions influenced the degree and rate of lipolysis. Additionally, the micellar fraction analysis suggested that the nature and composition of the oleogelators in SM and SL also impacted lipolysis and the bioaccessibility of astaxanthin. Furthermore, interfacial binding of lipase and isothermal titration calorimetry (ITC) measurements revealed that the oleogel network within the oil phase of the emulsion acted as a physical barrier, hindering the interaction between lipase and lipid. Overall, ß-sitosterol oleogel-based emulsions offer a versatile platform for delivering hydrophobic molecules, enhancing the bioavailability of active compounds, and achieving sustained release.

Differential alteration in Lactiplantibacillus plantarum subsp. plantarum quorum-sensing systems and reduced Candida albicans yeast survival and virulence gene expression in dual-species interaction.

Candida albicans (C. albicans) and Lactiplantibacillus plantarum subsp. plantarum (L. plantarum) are frequently identified in various niches, but their dual-species interaction, especially with C. albicans in yeast form, remains unclear. This study aimed to investigate the dual-species interaction of L. plantarum and C. albicans, including proliferation, morphology, and transcriptomes examined by selective agar plate counting, microscopy, and polymicrobial RNA-seq, respectively. Maintaining a stable and unchanged growth rate, L. plantarum inhibited C. albicans yeast cell proliferation but not hyphal growth. Combining optical microscopy and atomic force microscopy, cell-to-cell direct contact and co-aggregation with L. plantarum cells surrounding C. albicans yeast cells were observed during dual-species interaction. Reduced C. albicans yeast cell proliferation in mixed culture was partially due to L. plantarum cell-free culture supernatant but not the acidic environment. Upon polymicrobial transcriptomics analysis, interesting changes were identified in both L. plantarum and C. albicans gene expression. First, two L. plantarum quorum-sensing systems showed contrary changes, with the activation of lamBDCA and repression of luxS. Second, the upregulation of stress response-related genes and downregulation of cell cycle, cell survival, and cell integrity-related pathways were identified in C. albicans, possibly connected to the stress posed by L. plantarum and the reduced yeast cell proliferation. Third, a large scale of pathogenesis and virulence factors were downregulated in C. albicans, indicating the potential interruption of pathogenic activities by L. plantarum. Fourth, partial metabolism and transport pathways were changed in L. plantarum and C. albicans. The information in this study might aid in understanding the behavior of L. plantarum and C. albicans in dual-species interaction.IMPORTANCEThe anti-Candida albicans activity of Lactiplantibacillus plantarum has been explored in the past decades. However, the importance of C. albicans yeast form and the effect of C. albicans on L. plantarum had also been omitted. In this study, the dual-species interaction of L. plantarum and C. albicans was investigated with a focus on the transcriptomes. Cell-to-cell direct contact and co-aggregation with L. plantarum cells surrounding C. albicans yeast cells were observed. Upon polymicrobial transcriptomics analysis, interesting changes were identified, including contrary changes in two L. plantarum quorum-sensing systems and reduced cell survival-related pathways and pathogenesis determinants in C. albicans.

Sub-MIC streptomycin and tetracycline enhanced Staphylococcus aureus Guangzhou-SAU749 biofilm formation, an in-depth study on transcriptomics.

Staphylococcus aureus is a major human pathogen, a potential "Super-bug" and a typical biofilm forming bacteria. With usage of large amount of antibiotics, the residual antibiotics in clinical settings further complicate the colonization, pathogenesis and resistance of S. aureus. This study aimed at investigating the phenotypical and global gene expression changes on biofilm formation of a clinical S. aureus isolate treated under different types of antibiotics. Firstly, an isolate Guangzhou-SAU749 was selected from a large sale of previously identified S. aureus isolates, which exhibited weak biofilm formation in terms of biomass and viability. Secondly, 9 commonly prescribed antibiotics for S. aureus infections treatment, together with 10 concentrations ranging from 1/128 to 4 minimum inhibitory concentration (MIC) with 2-fold serial dilution, were used as different antibiotic stress conditions. Then, biofilm formation of S. aureus Guangzhou-SAU749 at different stages including 8 h, 16 h, 24 h, and 48 h, was tested by crystal violet and MTS assays. Thirdly, the whole genome of S. aureus Guangzhou-SAU749 was investigated by genome sequencing on PacBio platform. Fourthly, since enhancement of biofilm formation occurred when treated with 1/2 MIC tetracycline (TCY) and 1/4 MIC streptomycin (STR) since 5 h, the relevant biofilm samples were selected and subjected to RNA-seq and bioinformatics analysis. Last, expression of two component system (TCS) and biofilm associated genes in 4 h, 8 h, 16 h, 24 h, and 48 h sub-MIC TCY and STR treated biofilm samples were performed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Although most antibiotics lowered the biomass and cell viability of Guangzhou-SAU749 biofilm at concentrations higher than MIC, certain antibiotics including TCY and STR promoted biofilm formation at sub-MICs. Additionally, upon genome sequencing, RNA-seq and RT-qPCR on biofilm samples treated with sub-MIC of TCY and STR at key time points, genes lytR, arlR, hssR, tagA, clfB, atlA and cidA related to TCS and biofilm formation were identified to contribute to the enhanced biofilm formation, providing a theoretical basis for further controlling on S. aureus biofilm formation.

Antimicrobial Resistance, SCCmec, Virulence and Genotypes of MRSA in Southern China for 7 Years: Filling the Gap of Molecular Epidemiology.

As the prevalence of Staphylococcus aureus infections is of worldwide concern, phenotype and genotype in prevalent MRSA strains require longitudinal investigation. In this study, the antibiotic resistance, virulence gene acquisition, and molecular type were determined on a large scale of nosocomial S. aureus strains in Southern China during 2009-2015. Bacterial identification and antimicrobial susceptibility to 10 antibiotics were tested by Vitek-2. Virulence genes encoding staphylococcal enterotoxins (SEA, SEB, SEC, SED, and SEE), exfoliative toxins (ETA and ETB), Panton-Valentine leukocidin (PVL), and toxic shock syndrome toxin (TSST) were detected by PCR, with SCCmec typing also conducted by multiplex PCR strategy. Genotypes were discriminated by MLST and spaA typing. MLST was performed by amplification of the internal region of seven housekeeping genes. PCR amplification targeting the spa gene was performed for spa typing. No resistance to vancomycin, linezolid, or quinupristin and increase in the resistance to trimethoprim/sulfamethoxazole (55.5%) were identified. A total of nine SCCmec types and subtypes, thirteen STs clustered into thirteen spa types were identified, with ST239-SCCmec III-t037 presenting the predominant methicillin-resistant S. aureus (MRSA) clone. Typically, SCCmec type IX and ST546 were emergent types in China. Isolates positive for both pvl and tsst genes and for both eta and etb genes were also identified. Important findings in this study include: firstly, we have provided comprehensive knowledge on the molecular epidemiology of MRSA in Southern China which fills the gap since 2006 or 2010 from previous studies. Secondly, we have presented the correlation between virulence factors (four major groups) and genotypes (SCCmec, ST and spa types). Thirdly, we have shown evidence for earliest emergence of type I SCCmec from 2012, type VI from 2009 and type XI from 2012 in MRSA from Southern China.

Microbial Interaction between Lactiplantibacillus plantarum and Saccharomyces cerevisiae: Transcriptome Level Mechanism of Cell-Cell Antagonism.

Lactiplantibacillus plantarum and Saccharomyces cerevisiae are frequently co-isolated in food, although playing different roles. This study aimed at investigating the microbial interaction between L. plantarum and S. cerevisiae, especially cell-cell direct interaction and their mechanism. Cell-cell and supernatant-cell coculture models were set up, with CFU counting, OD600 measurement, optical and atomic force microscopy performed to examine the growth and morphology of L. plantarum and S. cerevisiae cells. In cell-cell coculture model, L. plantarum cells inhibited S. cerevisiae growth (inhibition rate ~80%) with its own growth pattern unaffected. Cell-cell aggregation happened during coculture with surface roughness changed and partial S. cerevisiae cell lysis. Mature (24 h) L. plantarum cell-free culture supernatant showed inhibition (35%-75%) on S. cerevisiae growth independent of pH level, while supernatant from L. plantarum-S. cerevisiae coculture showed relatively stronger inhibition. Upon transcriptomics analysis, hypothesis on the mechanism of microbial interaction between L. plantarum and S. cerevisiae was demonstrated. When L. plantarum cell density reached threshold at 24 h, all genes in lamBDCA quorum sensing (QS) system was upregulated to potentially increase adhesion capability, leading to the aggregation to S. cerevisiae cell. The downregulation of whole basic physiological activity from DNA to RNA to protein, cell cycle, meiosis, and mitogen-activated protein kinase (MAPK) signaling pathways, as well as growth maintenance essential genes ari1, skg6, and kex2/gas1 might induce the decreased growth and proliferation rate and partial death of S. cerevisiae cells in coculture. IMPORTANCE L. plantarum and S. cerevisiae are frequently co-isolated in food, although playing different roles. The co-existence of L. plantarum and S. cerevisiae could result in variable effects, raising economic benefits and safety concerns in food industry. Previous research has reported the microbial interaction between L. plantarum and S. cerevisiae mainly rely on the signaling through extracellular metabolites. However, cell-cell aggregation has been observed with mechanism remain unknown. In the current study, the microbial interaction between L. plantarum and S. cerevisiae was investigated with emphasis on cell-cell direct interaction and further in-depth transcriptome level study showed the key role of lamBDCA quorum sensing system in L. plantarum. The results yield from this study demonstrated the antagonistic effect between L. plantarum and S. cerevisiae.

Verification and application of a modified carbapenem inactivation method (mCIM) on Pseudomonas aeruginosa: a potential screening methodology on carbapenemases phenotype in Bacillus cereus.

Antimicrobial resistance (AMR) has been a leading issue for human health globally threatening the achievement of several of the Sustainable Development Goals (SDGs). Originated from Bacillus cereus, carbapenemases phenotype has been considered to be a major concern in AMR. In this study, the AMR identification rate of P. aeruginosa isolates and infections in FAHJU showed an obvious upward trend from 2012 to 2016. All 88 carbapenem-resistant P. aeruginosa strains were screened for carbapenemase phenotype by modified Carbapenem Inactivation Method (mCIM), and these results of mCIM were compared with traditional PCR results. The isolates of P. aeruginosa and infected patients showed obvious upward trend from 2012 to 2016. The drug resistance to common clinical antibiotics was serious that the clinical rational use of antibiotics should be strengthened, which is in accordance with the Global Antimicrobial Resistance and Use Surveillance System (GLASS) report. In comparison, the results of mCIM showed that 18 out of 88 CRPA strains were carbapenemase positive, which were completely consistent with the results yielded by PCR method. Therefore, it is convinced that this mCIM methodology is a simple and quick method for detected carbapenemases producing P. aeruginosa and has a potential capability in carbapenemases phenotype of pathogen like B. cereus, which will undoubtedly aid in the AMR therapy.

Establishment and application of a rapid visual detection method for Listeria monocytogenes based on polymerase spiral reaction (PSR).

Listeria monocytogenes is a common foodborne pathogen that presents in various food products, posing important threat to public health. The aim of this study was to establish a rapid and sensitive method with visualization to detect L. monocytogenes based on polymerase spiral reaction (PSR). Primers targeting conserved hlyA gene sequence of L. monocytogenes were designed based on bioinformatics analyses on the current available L. monocytogenes genomes. The isothermal amplification PSR can be completed under constant temperature (65ᵒC) within 60 min with high specificity and sensitivity. Twenty-five reference strains were used to evaluate the specificity of the developed reaction. The results showed that the sensitive of the reaction for L. monocytogenes in purified genomic DNA and artificially contaminated food samples were 41 pg/µL and 103 CFU/mL, respectively. It was 100-fold more sensitive than conventional PCR. In conclusion, this novel PSR method is rapid, cost-efficient, timesaving, and applicable on artificially contaminated food samples, providing broad prospects into the detection of foodborne microbes with the promising on-site inspection.

A strategy design based on antibiotic­resistance and plasmid replicons genes of clinical Escherichia coli strains.

Since antimicrobial resistance, especially ß-lactam resistance genes were common in clinical Escherichia coli strains, this study had designed and developed multiplex amplification platform for rapid and accurate detection of such resistance genes in 542 clinical E. coli isolates. The obtained specimens were subjected to bacteriological examination, antimicrobial susceptibility testing, and detection of ß-lactamase genes and plasmid replicons. The major virulence genes were detected by 7 groups of multiplex PCR and eight groups of multiplex PCR were designed to detect 8 different plasmid replicons including parA-parB, iteron, repA, and RNAI. It was found that most MDR isolates were co-resistant to penicillins (AMP) and fluoroquindones (LVX, CIP) and distribution of LVX and CIP resistance was significantly higher among female than male gender. RNAI (AY234375) showed the highest detection rate, followed by the iteron (J01724) and repA (M26308), indicating the relatively higher carriage rate of corresponding plasmids. BlaOXA acquired the highest carriage rate, followed by group 2 blaCTX-M and blaSHV-1, indicating their prevalence among clinical E. coli. Among the ß-lactamase genes, blaOXA acquired the highest carriage rate, followed by group 2 blaCTX-M and blaSHV-1, indicating their prevalence among clinical E. coli. The RNAI (AY234375) showed the highest detection rate, followed by the iteron (J01724) and repA (M26308), indicating the relatively higher carriage rate of the corresponding plasmids by clinical E. coli isolates. It is shown that the developed multiplex amplification methodology is applicable to AMR detection, and such identification of plasmid replicons and ß-lactamase genes may aid in the understanding of clinical E. coli isolate epidemiology.

Regulatory network controls microbial biofilm development, with Candida albicans as a representative: from adhesion to dispersal.

Microorganisms mainly exist in the form of biofilm in nature. Biofilm can contaminate food and drinking water system, as well as cause chronic wound infections, thereby posing a potential threat to public health safety. In the last two decades, researchers have made efforts to investigate the genetic contributors control different stages of biofilm development (adherence, initiation, maturation, and dispersal). As an opportunistic pathogen, C. albicans causes severe superficial or systemic infections with high morbidity and mortality under conditions of immune dysfunction. It has been reported that 80% of C. albicans infections are directly or indirectly associated with biofilm formation on host or abiotic surfaces including indwelling medical devices, resulting in high morbidity and mortality. Significantly, the outcome of C. albicans biofilm development includes enhanced invasion, exacerbated inflammatory responses and intrinsic resistance to antimicrobial chemotherapy. Thus, this review aimed at providing a comprehensive overview of the regulatory network controls microbial biofilm development, with C. albicans as a representative, served as reference for therapeutic targets.

Significant downtrend of antimicrobial resistance rate and rare ß-lactamase genes and plasmid replicons carriage in clinical Pseudomonas aeruginosa in Southern China.

OBJECTIVES: Pseudomonas aeruginosa is a medically important pathogen showing intrinsic low permeability to various antimicrobial agents and its potential to acquire multiple resistance mechanism. A longitudinal surveillance aimed to investigate the antimicrobial resistance and its determinants of Pseudomonas aeruginosa in Southern China. A total of 2163 P. aeruginosa isolates were obtained from patients in Southern China during 2004-2016. METHODS: The antimicrobial susceptibility of the isolates was performed by disk diffusion and Vitek 2 automated system and interpreted according to the Clinical and Laboratory Standard Institute (CLSI) 2015. RESULTS: A significant downtrend of resistant rate (>10.0%) was observed for tested antibiotic agents including ciprofloxacin (>30.0%), gentamicin (29.0%), tobramycin (24.2%) and ceftazidime (24.0%) except for aztreonam and amikacin. A total of 269 randomly selected isolates were further studied on the carriage of ß-lactam resistance genes by using 7 groups of multiplex PCRs targeting on 20 genes. ß-lactam resistance genes were rarely detected with a rate lower than 8%. Among all ß-lactam resistance genes, blaSHV acquired the highest identification rate (18/269, 6.7%), followed by blaOXA-1-like (6/269, 2.2%) and blaPER (6/269, 2.2%). In addition, 8 different plasmid replicons were amplified using 8 groups of multiplex PCRs including 18 sets of primers. Only five plasmid replicons were identified in 5 different P. aeruginosa isolates. Insignificant clonal relatedness among the positive strains identified by regular PCR were further verified by randomly amplified polymorphic DNA (RAPD)-PCR. CONCLUSION: This study has provided comprehensive knowledge on current antimicrobial resistance, ß-lactam resistance genes and plasmid replicons carriage in a large scale of clinical P. aeruginosa isolates.

Impact of pmrA on Cronobacter sakazakii planktonic and biofilm cells: A comprehensive transcriptomic study.

Cronobacter sakazakii is an emerging opportunistic foodborne pathogen causing rare but severe infections in neonates. Furthermore, the formation of biofilm allows C. sakazakii to persist in different environments. We have demonstrated that the mutator phenotype ascribed to deficiency of the pmrA gene results in more biomass in the first 24 h but less during the post maturation stage (7-14 d) compared with BAA 894. The present study aimed to investigate the regulatory mechanism modulating biofilm formation due to pmrA mutation. The transcriptomic analyses of BAA 894 and s-3 were performed by RNA-sequencing on planktonic and biofilm cells collected at different time points. According to the results, when comparing biofilm to planktonic cells, expression of genes encoding outer membrane proteins, lysozyme, etc. were up-regulated, with LysR family transcriptional regulators, periplasmic proteins, etc. down-regulated. During biofilm formation, cellulose synthase operon genes, flagella-related genes, etc. played essential roles in different stages. Remarkably, pmrA varies the expression of a number of genes related to motility, biofilm formation, and antimicrobial resistance, including srfB, virK, mviM encoding virulence factor, flgF, fliN, etc. encoding flagellar assembly, and marA, ramA, etc. encoding AraC family transcriptional regulators in C. sakazakii. This study provides valuable insights into transcriptional regulation of C. sakazakii pmrA mutant during biofilm formation.

Polymicrobial interaction between Lactobacillus and Saccharomyces cerevisiae: coexistence-relevant mechanisms.

The coordination of single or multiple microorganisms are required for the manufacture of traditional fermented foods, improving the flavour and nutrition of the food materials. However, both the additional economic benefits and safety concerns have been raised by microbiotas in fermented products. Among the fermented products, Lactobacillus and Saccharomyces cerevisiae are one of the stable microbiotas, suggesting their interaction is mediated by coexistence-relevant mechanisms and prevent to be excluded by other microbial species. Thus, aiming to guide the manufacture of fermented foods, this review will focus on interactions of coexistence-relevant mechanisms between Lactobacillus and S. cerevisiae, including metabolites communications, aggregation, and polymicrobial biofilm. Also, the molecular regulatory network of the coexistence-relevant mechanisms is discussed according to omics researches.

Antimicrobial susceptibility and genetic features of a heterogeneous vancomycin intermediate-resistant Staphylococcus aureus strain.

This study aimed to characterize the antimicrobial susceptibility and genetic features of a heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) strain Guangzhou-SauVS2 recovered from a female patient in Guangzhou, representative of southern China. The genome of Guangzhou-SauVS2 was sequenced using Illumina HiSeq 2500 platform and assembled de novo using Velvet v1.2.08. Annotations and bioinformatics analysis were further performed. Results showed that Guangzhou-SauVS2 was susceptible and resistant to 7 and 11 antibiotic drugs, respectively, and exhibited hVISA with a minimum inhibitory concentration of vancomycin as 4 µg/mL. Its genome is 2,883,941 bp in length and contains 2934 predicted genes with an average G + C content of 32.9%. Besides, a total of 38 virulence factors and 4 antibiotic-resistant genes were identified. These results can be employed to further study the pathogenic and antimicrobial mechanisms of hVISA.

Resistome and virulome study on pathogenic Streptococcus agalactiae Guangzhou-SAG036.

Streptococcus agalactiae is considered as a leading case of bacterial infection among neonates. Although relative protection strategies have been performed in many high-income countries, resulting in a massive reduction in the occurrences of early-onset GBS disease, the late-onset disease has not affected. Here, the whole genome of S. agalactiae Guangzhou-SAG036 was sequenced by the Pacific Biosciences Sequel using the P4-C2 chemistry and the continuous long reads were used for de novo assembly using HGAP. Besides, genes prediction and multiply annotation were performed by comparing it with diverse databases. The whole genome has a length of 2,206,504 bp and contains 2162 predicted genes with an average G + C content of 35.85%. Based on the whole genome sequence, 2 large prophages, 20 virulence factors genes, and 8 antibiotic resistant genes were identified. MLST analysis revealed S. agalactiae Guangzhou-SAG036 was identified as ST-17. The virulence factors genes were identified with different functions including adherence, antiphagocytosis, spreading factor, immune evasion, invasion, toxin. Besides, the antibiotic-resistant genes may provide S. agalactiae with resistance to multi-drugs including erythromycin, streptomycin, azithromycin, spiramycin, ampicillin, kanamycin, cationic peptides, and tetracycline. Therefore, the infection of S. agalactiae Guangzhou-SAG036 ST-17 strain maybe caused by the complex virulence factors and multi-drugs resistance. These results contribute to further understand GBS epidemiology and surveillance targets.

Genomic analysis of a hop-resistance Lactobacillus brevis strain responsible for food spoilage and capable of entering into the VBNC state.

BACKGROUND: Lactobacillus brevis is a major contaminant of spoiled beer. And it was able to enter VBNC state and cause false negative detection, which poses a major challenge to the brewing industry. METHODS: The genomic DNA of L. brevis BM-LB13908 was extracted and purified to form a sequencing library that meets the quality requirements and was sequenced. The sequencing results were then screened and assembled to obtain the entire genome sequence of L. brevis. Predicted genes were annotated by GO database, KEGG pathway database and COG functional classification system. RESULTS: The final assembly yielded 275 scaffolds of a total length of 2 840 080 bp with a G + C content of 53.35%. There were 2357, 701, 1519 predicted genes with corresponding GO functional, COG functional, and KEGG biological pathway annotations, respectively. The genome of L. brevis BM-LB13908 contains hop resistance gene horA and multiple genes related to the formation of VBNC state. CONCLUSIONS: This report describes the draft genome sequence of L. brevis BM-LB13908, a spoilage strain isolated from finished beer sample. This study may support further study on L. brevis and other beer spoilage bacteria, and prevent and control beer spoilage caused by microorganisms.

Spoilage Lactic Acid Bacteria in the Brewing Industry.

Lactic acid bacteria (LAB) have caused many microbiological incidents in the brewing industry, resulting in severe economic loss. Meanwhile, traditional culturing method for detecting LAB are time-consuming for brewers. The present review introduces LAB as spoilage microbes in daily life, with focus on LAB in the brewing industry, targeting at the spoilage mechanism of LAB in brewing industry including the special metabolisms, the exist of the viable but nonculturable (VBNC) state and the hop resistance. At the same time, this review compares the traditional and novel rapid detection methods for these microorganisms which may provide innovative control and detection strategies for preventing alcoholic beverage spoilage, such as improvement of microbiological quality control using advanced culture media or different isothermal amplification methods.

Inhibitory effects of two types of food additives on biofilm formation by foodborne pathogens.

The inhibition of microbial biofilms is a significant concern in food safety. In the present study, the inhibitory effect of sodium citrate and cinnamic aldehyde on biofilm formation at minimum inhibitory concentrations (MICs) and sub-MICs was investigated for Escherichia coli O157:H7 and Staphylococcus aureus. The biofilm inhibition rate was measured to evaluate the effect of sodium citrate on S. aureus biofilms at 24, 48, 72, and 96 hr. According to the results, an antibiofilm effect was shown by both food additives, with 10 mg/ml of sodium citrate exhibiting the greatest inhibition of S. aureus biofilms at 24 hr (inhibition rate as high as 77.51%). These findings strongly suggest that sodium citrate exhibits a pronounced inhibitory effect on biofilm formation with great potential in the extension of food preservation and storage.

Biofilm Formation of Staphylococcus aureus under Food Heat Processing Conditions: First Report on CML Production within Biofilm.

This study aimed to evaluate the Staphylococcus aureus biofilm formation and Nε-carboxymethyl-lysine generation ability under food heat processing conditions including pH (5.0-9.0), temperature (25 °C, 31 °C, 37 °C, 42 °C and 65 °C), NaCl concentration (10%, 15% and 20%, w/v) and glucose concentration (0.5%, 1%, 2%, 3%, 5%, 10%, w/v). S. aureus biofilm genetic character was obtained by PCR detecting atl, ica operon, sasG and agr. Biofilm biomass and metabolic activity were quantified with crystal violet and methyl thiazolyl tetrazolium staining methods. S. aureus biofilm was sensitive to food heat processing conditions with 37 °C, pH 7.0, 2% glucose concentration (w/v) and 10% NaCl concentration (w/v) were favorable conditions. Besides, free and bound Nε-carboxymethyl-lysine level in weak, moderate and strong biofilm were detected by optimized high performance liquid chromatography tandem mass spectrometry. Nε-carboxymethyl-lysine level in S. aureus biofilm possessed a significant gap between strong, moderate and weak biofilm strains. This investigation revealed the biological and chemical hazard of Staphylococcus aureus biofilm to food processing environment.

Protective effects of polyphenolic extracts from longan seeds promote healing of deep second-degree burn in mice.

The objective of this study was to evaluate the ability of a polyphenolic extract from longan seeds as a wound-healing material for deep second-degree burn wounds. The total phenol content of the extract reached 45.28 ± 1.22 mg GAE per g DW when 70% ethanol was used as the extraction solvent, and then AB-8 resin was used for purification. Results from the antioxidant assay in vitro (DPPH˙ and hydroxyl radical scavenging activity) and antimicrobial activity assay (ZOI, MIC and MBC) showed that the fractions eluted by 30% ethanol tend to have greater antioxidant ability, as well as higher bactericidal and antibacterial activities, than the other elution fractions. Low-, middle-, and high-doses of the polyphenolic extract were applied for wound-healing of mice, and were compared with 30% ethanol solution (negative control) and 'Jing Wan Hong®' (positive control). The results showed that on the 11th day, the wound-healing rate and levels of hydroxyproline and protein indicated that wound healing in the high-dose polyphenolic group was similar to that of the positive control, which was higher than that in the other groups (p < 0.01). The histological results indicated that high-dose polyphenolic extracts are capable of leading to the formation of new blood vessels and capillaries, regenerating new dermal tissue and remodeling the newly formed tissue during the proliferative period. Our results provided first-hand information on the would-healing potential of the polyphenolic extract from longan seeds.