Bacillus cereus,a spore-forming bacterium and frequent cause of food poisoning,poses a safety threat to dairy and rice industries due to its high contamination rates and ability to produce toxins such as cereulide.Bec...Bacillus cereus,a spore-forming bacterium and frequent cause of food poisoning,poses a safety threat to dairy and rice industries due to its high contamination rates and ability to produce toxins such as cereulide.Because of widespread presence and thermal resistance of the spores,B.cereus cannot be eliminated from the environment and may survive in processing plants.Surviving spores can develop into vegetative cells,leading to a heightened risk of cereulide production in the processing environment.Both spores and vegetative cells have the ability to adhere to the surfaces of dairy plants and form biofilms,serving as the site for cereulide production and accumulation.Therefore,it is crucial for the food industry to address potential sources and pathways of B.cereus contamination and their connections to cereulide production in processing lines.In this review,sources of contamination of B.cereus,including spores,vegetative cells,and biofilms and their potential role in cereulide production at each stage of dairy and cooked rice processing were analyzed.In addition,control methods to prevent B.cereus contamination and cereulide production in processing lines were proposed,offering valuable insights for improving microbial risk management in the food industry.展开更多
Heterogeneous Pd nanocatalysts are efficient catalysts for the Heck reaction but require multi-step,sophisticated procedures and harsh reaction conditions.In this work,a green and facile strategy has been developed to...Heterogeneous Pd nanocatalysts are efficient catalysts for the Heck reaction but require multi-step,sophisticated procedures and harsh reaction conditions.In this work,a green and facile strategy has been developed to decorate Pd nanoparticles on polydopamine(PDA)-coated multi-walled carbon nanotubes(Pd/CNTs-PDA)via a one-pot method.The obtained nanoparticles were characterized by various techniques including transmission electron microscopy,X-ray diffraction,and X-ray photoelectron spectroscopy,which proved that Pd NPs are well-dispersed on the PDA and between the surfaces of the PDA and CNTs.The resultant Pd/CNTs-PDA catalysts exhibit excellent catalytic reactivity toward the Heck reaction at low temperatures.Moreover,by DFT simulation,we found that during the PDA polymerization process,a large number of unsaturated—N=and C=O species are more active than the groups on the PDA end product to anchor Pd NPs.The results provide evidence that the catalyst synthesized by the onepot method exhibited good activity because sufficient active sites could be created to effectively promote Pd NPs dispersion during the dopamine polymerization process.Additionally,the Pd/CNTs-PDA catalyst was successfully employed in Heck cross-coupling reactions with various functionalized substrates.This method opens a window for the fabrication of high-performance nanocomposite catalysts under mild conditions using simple methods and has several potential applications.展开更多
This study investigated the microbial contamination of ice cream in China.A total of 2887 ice cream samples were collected from different regions of China.Contamination by the aerobic plate count(APC),coliforms,and th...This study investigated the microbial contamination of ice cream in China.A total of 2887 ice cream samples were collected from different regions of China.Contamination by the aerobic plate count(APC),coliforms,and three foodborne pathogens,Listeria monocytogenes(L.monocytogenes),Staphylococcus aureus(S.aureus),and Salmonella spp.,was detected in the samples.L.monocytogenes isolates were further analyzed for antibiotic susceptibility and multi-locus sequence typing(MLST).The results showed that APC was more than 10^(5) colony forming units(CFU)/g in 6.10%(176/2887)and coliform was more than 10^(2) CFU/g in 15.69%(453/2887)of all samples.The positive rates of S.aureus,L.monocytogenes,and Salmonella spp.were 0.66%,0.62%,and 0.10%,respectively.Among these,S.aureus contamination was more than 102 CFU/g in two samples,and L.monocytogenes in the positive sample was in the range of 0.3-240 most probable number(MPN)/g.with a median of 4.3 MPN/g.The hygienic status of the packaged samples was much better than that of the bulk samples(P<0.05).Catering samples were more frequently and heavily contaminated than samples from retail and wholesale outlets(P<0.05).No significant differences were observed in samples bought from urban and rural areas(P>0.05).For 18 L.monocytogenes strains isolated from ice cream,the resistance rate of nine antibiotics was 5.56%(1/18).By MLST,the L.monocytogenes strains were classified into nine sequence types(STs),of which ST8 was the most common(six isolates).These results indicate that a potential health risk to the public may be caused by ice cream,particularly in susceptiblepopulations.展开更多
基金This work was funded by a grant from the Key Projects of International Scientific and Technological Innovation Cooperation Among Governments Under the National Key Research and Development Program of China(No.2019YFE0103800).
文摘Bacillus cereus,a spore-forming bacterium and frequent cause of food poisoning,poses a safety threat to dairy and rice industries due to its high contamination rates and ability to produce toxins such as cereulide.Because of widespread presence and thermal resistance of the spores,B.cereus cannot be eliminated from the environment and may survive in processing plants.Surviving spores can develop into vegetative cells,leading to a heightened risk of cereulide production in the processing environment.Both spores and vegetative cells have the ability to adhere to the surfaces of dairy plants and form biofilms,serving as the site for cereulide production and accumulation.Therefore,it is crucial for the food industry to address potential sources and pathways of B.cereus contamination and their connections to cereulide production in processing lines.In this review,sources of contamination of B.cereus,including spores,vegetative cells,and biofilms and their potential role in cereulide production at each stage of dairy and cooked rice processing were analyzed.In addition,control methods to prevent B.cereus contamination and cereulide production in processing lines were proposed,offering valuable insights for improving microbial risk management in the food industry.
基金supported by the National Natural Science Foundation of China(Nos.21506174,21406039)the Fundamental Research Funds for the Central Universities,Southwest Minzu University(2020NYBPY04)+1 种基金the China Scholarship Council Program(201908510082)Guangdong Natural Science Foundation(2017A030307038)。
文摘Heterogeneous Pd nanocatalysts are efficient catalysts for the Heck reaction but require multi-step,sophisticated procedures and harsh reaction conditions.In this work,a green and facile strategy has been developed to decorate Pd nanoparticles on polydopamine(PDA)-coated multi-walled carbon nanotubes(Pd/CNTs-PDA)via a one-pot method.The obtained nanoparticles were characterized by various techniques including transmission electron microscopy,X-ray diffraction,and X-ray photoelectron spectroscopy,which proved that Pd NPs are well-dispersed on the PDA and between the surfaces of the PDA and CNTs.The resultant Pd/CNTs-PDA catalysts exhibit excellent catalytic reactivity toward the Heck reaction at low temperatures.Moreover,by DFT simulation,we found that during the PDA polymerization process,a large number of unsaturated—N=and C=O species are more active than the groups on the PDA end product to anchor Pd NPs.The results provide evidence that the catalyst synthesized by the onepot method exhibited good activity because sufficient active sites could be created to effectively promote Pd NPs dispersion during the dopamine polymerization process.Additionally,the Pd/CNTs-PDA catalyst was successfully employed in Heck cross-coupling reactions with various functionalized substrates.This method opens a window for the fabrication of high-performance nanocomposite catalysts under mild conditions using simple methods and has several potential applications.
基金supported by the National Key Research and Development Program of China (2018YFC1604304)the National Risk Surveillance Fund in Chinathe National Natural Science Foundation of China (No.81773481).
文摘This study investigated the microbial contamination of ice cream in China.A total of 2887 ice cream samples were collected from different regions of China.Contamination by the aerobic plate count(APC),coliforms,and three foodborne pathogens,Listeria monocytogenes(L.monocytogenes),Staphylococcus aureus(S.aureus),and Salmonella spp.,was detected in the samples.L.monocytogenes isolates were further analyzed for antibiotic susceptibility and multi-locus sequence typing(MLST).The results showed that APC was more than 10^(5) colony forming units(CFU)/g in 6.10%(176/2887)and coliform was more than 10^(2) CFU/g in 15.69%(453/2887)of all samples.The positive rates of S.aureus,L.monocytogenes,and Salmonella spp.were 0.66%,0.62%,and 0.10%,respectively.Among these,S.aureus contamination was more than 102 CFU/g in two samples,and L.monocytogenes in the positive sample was in the range of 0.3-240 most probable number(MPN)/g.with a median of 4.3 MPN/g.The hygienic status of the packaged samples was much better than that of the bulk samples(P<0.05).Catering samples were more frequently and heavily contaminated than samples from retail and wholesale outlets(P<0.05).No significant differences were observed in samples bought from urban and rural areas(P>0.05).For 18 L.monocytogenes strains isolated from ice cream,the resistance rate of nine antibiotics was 5.56%(1/18).By MLST,the L.monocytogenes strains were classified into nine sequence types(STs),of which ST8 was the most common(six isolates).These results indicate that a potential health risk to the public may be caused by ice cream,particularly in susceptiblepopulations.
