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Myoung Soo Nam - One of the best experts on this subject based on the ideXlab platform.
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Effects of Psychrotrophic Bacteria, Serratia liquefaciens and Acinetobacter genomospecies 10 on Yogurt Quality.
Korean journal for food science of animal resources, 2014Co-Authors: Yong Kook Shin, Hyun Ah Lee, Jong-woo Choi, Myoung Soo NamAbstract:The aim of this study was to evaluate the effect of proteolytic (Serratia liquefaciens, match %: 99.39) or lipolytic (Acinetobacter genomospecies 10, match %: 99.90) Psychrotrophic Bacteria (Bacterial counts, analysis of free fatty acids (FFA) and analysis of free amino acids) on the microbial and chemical properties (yogurt composition), and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of yogurt during storage. Yogurts were prepared with raw milk preinoculated with each Psychrotrophic Bacteria. The total solid, fat, and protein content were not affected by preinoculation, but the pH of yogurt preinoculated with Psychrotrophic Bacteria was higher than in control. There was a dramatic increase in short chain free fatty acids among FFA in yogurt with Acinetobacter genomospecies 10. For 14 d of cold storage condition, SCFFA was 25.3 mg/kg to 34.4 mg/kg (1.36 times increased), MCFFA was 20.4 mg/kg to 25.7 mg/kg (1.26 times increased), and LCFFA was 240.2 mg/kg to 322.8 mg/kg (1.34 times increased). Serratia liquefaciens (match %: 99.39) in yogurt caused a greater accumulation of free amino acids (FAA), especially bitter peptides such as leucine, valine, arginine, and tyrosine, but SDS-PAGE showed that the inoculation of Serratia liquefaciens did not affect the degree of casein degradation during storage. Taken together, the excessive peptides and FFA in yogurt generated from Psychrotrophic Bacteria could develop off-flavors that degrade the quality of commercial yogurt products.
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enzyme activity of isolated Psychrotrophic Bacteria from raw milk of different regions on season
Korean Journal for Food Science of Animal Resources, 2013Co-Authors: Yong Kook Shin, Hyun Ah Lee, Myoung Soo NamAbstract:The aim of this study was to investigate the effect of season and location on activities of enzyme produced by Psychrotrophic Bacteria isolated from raw milk located in Kyunggi region of South Korea. Agar diffusion and colorimetric methods were used for the lipase and protease activities of Psychrotrophic Bacteria. Intensities of dark blue and transparent ring around colony were compared for activity measurement. Nutrient agar with 1% skim milk added was employed for measuing protease activity. 14 strains of Arthrobacter russicus with lipase activity and 19 strains of Chryserobacterium shigense with protease activities were found to be present. It was found that Acinetobacter genomospecies 10 (match %: 99.90) isolated from B region in fall was the most lipolytic species, whereas Serratia liquefaciens (match %: 99.39) isolated from the same region in spring was the most proteolytic species. Growth curve of Acinetobacte and Serratia liquefaciens was a typical sigmoidal form. Lipase activity increased with incubation time, but its activity began to drop at stationary to motality phase. Optimum condition for incubation time, pH and temperature for extracellular lipase from Acinetobacter genomospecies 10 (match %: 99.90) was 12 h, 8.5, and 45 o C, respectively. Extracellular protease from Serratia liquefaciens (match %:99.39) had the same optimum incubation time and pH as extracellular lipase, but optimum temperature was 35 o C.
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effects of Psychrotrophic Bacteria acinetobacter genomospecies 10 and serratia liquefaciens on raw milk quality
Korean Journal for Food Science of Animal Resources, 2013Co-Authors: Yong Kook Shin, Hyun Ah Lee, Myoung Soo NamAbstract:This study was conducted to investigate effect of Psychrotrophic Bacteria on the quality of raw milk. Acinetobacter genomospecies 10 was selected as lipolytic species, and Serratia liquefaciens as proteolytic species. Lipase present in inoculated raw milk with Acinetobacter genomospecies 10 did not affect total solid and fat contents. However, the free fatty acid (FFA) content, especially short chain FFAs, of milk with Acinetobacter genomospecies 10 was dramatically increased. FFAs produced by lipolysis of milk fat are important in flavor of dairy products, excessive lipolysis occurring in milk and dairy products could cause off-flavor, and produced FFAs may have an underiable effect on their flavor. In addition, protease influenced the quality of inoculated raw milk with Serratia liquefaciens. In degradation patterns of casein by SDS-PAGE analysis from inoculatred raw milk with Serratia liquefaciens, casein content was gradually decreased during storage at 4 o C, and extensive degradation of κ-casein was observed on the storage day of 13. The free amino acids such as leucine, valine, arginine, and tyrosine were dramatically increased, which causes bitter taste in raw milk. These excessive peptides in dairy products, produced by Psychrotrophic Bacteria, can be possible to develop off-flavors and be responsible for gelling of milk by degradation.
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seasonal regional distribution and identification of Psychrotrophic Bacteria in milk
Korean Journal of Agricultural Science, 2013Co-Authors: Yong Kook Shin, Hyun Ah Lee, Myoung Soo NamAbstract:To investigate the distribution of Psychrotrophic Bacteria, raw milk was collected from farms in nine different regions located around Kyunggi province in South Korea at four different seasons. Psychrotrophic counts were higher in winter than in other seasons as 3.0×10 4 CFU/mL (p<0.05). Among nine regions, the population in raw milk sampled from B region was in significantly greater numbers and those from C and D province were in significantly lower numbers than any other regions, 2.4×10 5 CFU/mL and 8.7×10 3 CFU/mL, respectively (p<0.05). In addition, among 706 Bacterial isolates, the predominant class was Gamma-proteoBacteria (81.02%) and genus was Pseudomonas (32.34%), especially Pseudomonas fluorescens (39.46%). Compared to the regional predominance, Acinetobacter johnsonii in A region, Pseudomonas fluorescens in B region, Enterobacter amnigenus in C region, Psychrobacter maritimus in D region, Acinetobacter johnsonii in E region, Acinetobacter haemolyticus in F region, Pseudomonas fluorescens in G region, Acinetobacter jounsonii in H region, and Pseudomonas mucidolens in I region were found.
Pablo E. Hernández - One of the best experts on this subject based on the ideXlab platform.
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Monoclonal antibodies and an indirect ELISA for detection of Psychrotrophic Bacteria in refrigerated milk.
Journal of food protection, 1997Co-Authors: Rosalba Gutiérrez, Isabel González, Teresa García, Ester Carrera, Bernabé Sanz, Pablo E. Hernández, Rosario MartínAbstract:Monoclonal antibodies generated against live cells of Pseudomonas fluorescens have been used in an indirect ELISA format for the detection of Pseudomonas spp. and related Psychrotrophic Bacteria in refrigerated milk. The immunorecognition of monoclonal antibodies adsorbed to Bacteria bound to the wells of a microtiter plate was performed with rabbit anti-mouse immunoglobulins conjugated to horseradish peroxidase. Subsequent enzymic conversion of the substrate resulted in distinct absorbance differences when assaying milk samples containing Psychrotrophic Bacteria in the range 10(5) to 10(9) CFU ml(-1) . The detection threshold for the ELISA assay developed in this work is 10(5) CFU ml(-1).
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Detection of Psychrotrophic Bacteria on meat surfaces by an indirect ELISA using polyclonal antibodies against live cells of Pseudomonas fluorescens
Archiv Fur Lebensmittelhygiene, 1996Co-Authors: Isabel González, Teresa García, Bernabé Sanz, Rosario Martín, Paloma Morales, Pablo E. HernándezAbstract:Polyclonal antibodies raised against live cells of Pseudomonas (Ps.) fluorescens AH-70 have been used in an indirect enzyme-linked immunosorbent assay (ELISA) for detection of Ps. fluorescens and related Psychrotrophic Bacteria in refrigerated meat. These anti-live cells antibodies were recovered from the crude antiserum by ammonium sulfate precipitation and conjugated to biotin. Commercial ExtrAvidin-peroxidase conjugate was used to detect the biotinylated antibodies bound to their specific antigens. Subsequent enzymatic conversion of substrate gave distinct absorbance differences when assaying meat samples containing Ps. fluorescens strains of different origin as well as related Psychrotrophic microorganisms. The detection threshold for the ELISA assay developed in this work was 10 4 to 10 5 cfu/cm 2 .
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Polyclonal antibodies against protein F from the cell envelope of Pseudomonas fluorescens for the detection of Psychrotrophic Bacteria in refrigerated meat using an indirect ELISA.
Meat science, 1996Co-Authors: Isabel González, Teresa García, Bernabé Sanz, Rosario Martín, Paloma Morales, Pablo E. HernándezAbstract:Abstract An indirect enzyme-linked immunosorbent assay (ELISA) has been developed for detection of Pseudomonas fluorescens and related Psychrotrophic Bacteria in refrigerated meat. The ELISA uses polyclonal antibodies raised in rabbits against protein F from the cell envelope of Pseudomonas fluorescens AH-70. The anti-protein F antibodies were recovered from the crude antiserum by ammonium sulfate precipitation and conjugated to biotin. Commercial Extr Avidin-peroxidase conjugate was used to detect the biotinylated antibodies bound to their specific antigens. Subsequent enzymatic conversion of substrate gave distinct absorbance differences when assaying meat samples containing P. fluorescens strains of different origin as well as related Psychrotrophic microorganisms. The detection threshold for the ELISA assay developed in this work was 10 4 –10 5 cfu cm −2 .
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Detection of Pseudomonas fluorescens and Related Psychrotrophic Bacteria in Refrigerated Meat by a Sandwich ELISA.
Journal of food protection, 1994Co-Authors: Isabel González, Teresa García, Bernabé Sanz, Rosario Martín, Paloma Morales, Pablo E. HernándezAbstract:A sandwich enzyme-linked immunosorbent assay (ELISA) was developed for detection of Pseudomonas fluorescens and related Psychrotrophic Bacteria in refrigerated meat. Polyclonal antibodies were raised in rabbits against protein F from the cell envelope of P. fluorescens AH-70. The ELISA involved capturing antigens from the microorganisms present on meat samples with the anti-protein F antibodies immovilized on 96-well plates, and detecting bound antigens with the same anti-PF antibodies conjugated to biotin. Commercial ExtrAvidin-peroxidase conjugate was used to detect the biotinylated antibodies bound to their specific antigens. Subsequent enzymatic conversion of substrate gave distinct absorbance differences when assaying meat samples containing P. fluorescens strains of different origin as well as related Psychrotrophic microorganisms. The detection threshold for the ELISA assay developed in this work is 105 CFU/cm2.
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A sandwich enzyme‐linked immunosorbent assay (ELISA) for detection of Pseudomcnas fluorescens and related Psychrotrophic Bacteria in refrigerated milk
The Journal of applied bacteriology, 1993Co-Authors: Isabel González, Teresa García, Bernabé Sanz, Rosario Martín, Paloma Morales, Pablo E. HernándezAbstract:I. GONZALEZ, R. MARTIN, T. GARCIA, P. MORALES, B. SANZ AND P.E. HERNANDEZ. 1993. A sandwich ELISA (enz***me-linked immunosorbent assay) was developed for detection of Pseudomonas fluorescens and related Psychrotrophic Bacteria in refrigerated milk. Polyclonal antibodies were raised in rabbits against protein F from the cell envelope of Pseudomonas fluorescens AH-70. The anti-protein F antibodies (anti-PF) bound to the wells of a microtitre plate were used to capture this protein from the micro-organisms on milk samples. Further immunorecognition of the captured antigen was attained with the same anti-PF antibodies conjugated to biotin. ExtrAvidin-peroxidase was used to detect the biotinylated antibodies bound to their specific antigens. Subsequent enzymic conversion of substrate gave clear absorbance differences when assaying milk samples containing Ps. fluorescens strains of different origin as well as related Psychrotrophic micro-organisms.
Yong Kook Shin - One of the best experts on this subject based on the ideXlab platform.
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Effects of Psychrotrophic Bacteria, Serratia liquefaciens and Acinetobacter genomospecies 10 on Yogurt Quality.
Korean journal for food science of animal resources, 2014Co-Authors: Yong Kook Shin, Hyun Ah Lee, Jong-woo Choi, Myoung Soo NamAbstract:The aim of this study was to evaluate the effect of proteolytic (Serratia liquefaciens, match %: 99.39) or lipolytic (Acinetobacter genomospecies 10, match %: 99.90) Psychrotrophic Bacteria (Bacterial counts, analysis of free fatty acids (FFA) and analysis of free amino acids) on the microbial and chemical properties (yogurt composition), and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of yogurt during storage. Yogurts were prepared with raw milk preinoculated with each Psychrotrophic Bacteria. The total solid, fat, and protein content were not affected by preinoculation, but the pH of yogurt preinoculated with Psychrotrophic Bacteria was higher than in control. There was a dramatic increase in short chain free fatty acids among FFA in yogurt with Acinetobacter genomospecies 10. For 14 d of cold storage condition, SCFFA was 25.3 mg/kg to 34.4 mg/kg (1.36 times increased), MCFFA was 20.4 mg/kg to 25.7 mg/kg (1.26 times increased), and LCFFA was 240.2 mg/kg to 322.8 mg/kg (1.34 times increased). Serratia liquefaciens (match %: 99.39) in yogurt caused a greater accumulation of free amino acids (FAA), especially bitter peptides such as leucine, valine, arginine, and tyrosine, but SDS-PAGE showed that the inoculation of Serratia liquefaciens did not affect the degree of casein degradation during storage. Taken together, the excessive peptides and FFA in yogurt generated from Psychrotrophic Bacteria could develop off-flavors that degrade the quality of commercial yogurt products.
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enzyme activity of isolated Psychrotrophic Bacteria from raw milk of different regions on season
Korean Journal for Food Science of Animal Resources, 2013Co-Authors: Yong Kook Shin, Hyun Ah Lee, Myoung Soo NamAbstract:The aim of this study was to investigate the effect of season and location on activities of enzyme produced by Psychrotrophic Bacteria isolated from raw milk located in Kyunggi region of South Korea. Agar diffusion and colorimetric methods were used for the lipase and protease activities of Psychrotrophic Bacteria. Intensities of dark blue and transparent ring around colony were compared for activity measurement. Nutrient agar with 1% skim milk added was employed for measuing protease activity. 14 strains of Arthrobacter russicus with lipase activity and 19 strains of Chryserobacterium shigense with protease activities were found to be present. It was found that Acinetobacter genomospecies 10 (match %: 99.90) isolated from B region in fall was the most lipolytic species, whereas Serratia liquefaciens (match %: 99.39) isolated from the same region in spring was the most proteolytic species. Growth curve of Acinetobacte and Serratia liquefaciens was a typical sigmoidal form. Lipase activity increased with incubation time, but its activity began to drop at stationary to motality phase. Optimum condition for incubation time, pH and temperature for extracellular lipase from Acinetobacter genomospecies 10 (match %: 99.90) was 12 h, 8.5, and 45 o C, respectively. Extracellular protease from Serratia liquefaciens (match %:99.39) had the same optimum incubation time and pH as extracellular lipase, but optimum temperature was 35 o C.
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effects of Psychrotrophic Bacteria acinetobacter genomospecies 10 and serratia liquefaciens on raw milk quality
Korean Journal for Food Science of Animal Resources, 2013Co-Authors: Yong Kook Shin, Hyun Ah Lee, Myoung Soo NamAbstract:This study was conducted to investigate effect of Psychrotrophic Bacteria on the quality of raw milk. Acinetobacter genomospecies 10 was selected as lipolytic species, and Serratia liquefaciens as proteolytic species. Lipase present in inoculated raw milk with Acinetobacter genomospecies 10 did not affect total solid and fat contents. However, the free fatty acid (FFA) content, especially short chain FFAs, of milk with Acinetobacter genomospecies 10 was dramatically increased. FFAs produced by lipolysis of milk fat are important in flavor of dairy products, excessive lipolysis occurring in milk and dairy products could cause off-flavor, and produced FFAs may have an underiable effect on their flavor. In addition, protease influenced the quality of inoculated raw milk with Serratia liquefaciens. In degradation patterns of casein by SDS-PAGE analysis from inoculatred raw milk with Serratia liquefaciens, casein content was gradually decreased during storage at 4 o C, and extensive degradation of κ-casein was observed on the storage day of 13. The free amino acids such as leucine, valine, arginine, and tyrosine were dramatically increased, which causes bitter taste in raw milk. These excessive peptides in dairy products, produced by Psychrotrophic Bacteria, can be possible to develop off-flavors and be responsible for gelling of milk by degradation.
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seasonal regional distribution and identification of Psychrotrophic Bacteria in milk
Korean Journal of Agricultural Science, 2013Co-Authors: Yong Kook Shin, Hyun Ah Lee, Myoung Soo NamAbstract:To investigate the distribution of Psychrotrophic Bacteria, raw milk was collected from farms in nine different regions located around Kyunggi province in South Korea at four different seasons. Psychrotrophic counts were higher in winter than in other seasons as 3.0×10 4 CFU/mL (p<0.05). Among nine regions, the population in raw milk sampled from B region was in significantly greater numbers and those from C and D province were in significantly lower numbers than any other regions, 2.4×10 5 CFU/mL and 8.7×10 3 CFU/mL, respectively (p<0.05). In addition, among 706 Bacterial isolates, the predominant class was Gamma-proteoBacteria (81.02%) and genus was Pseudomonas (32.34%), especially Pseudomonas fluorescens (39.46%). Compared to the regional predominance, Acinetobacter johnsonii in A region, Pseudomonas fluorescens in B region, Enterobacter amnigenus in C region, Psychrobacter maritimus in D region, Acinetobacter johnsonii in E region, Acinetobacter haemolyticus in F region, Pseudomonas fluorescens in G region, Acinetobacter jounsonii in H region, and Pseudomonas mucidolens in I region were found.
Isabel González - One of the best experts on this subject based on the ideXlab platform.
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Monoclonal antibodies and an indirect ELISA for detection of Psychrotrophic Bacteria in refrigerated milk.
Journal of food protection, 1997Co-Authors: Rosalba Gutiérrez, Isabel González, Teresa García, Ester Carrera, Bernabé Sanz, Pablo E. Hernández, Rosario MartínAbstract:Monoclonal antibodies generated against live cells of Pseudomonas fluorescens have been used in an indirect ELISA format for the detection of Pseudomonas spp. and related Psychrotrophic Bacteria in refrigerated milk. The immunorecognition of monoclonal antibodies adsorbed to Bacteria bound to the wells of a microtiter plate was performed with rabbit anti-mouse immunoglobulins conjugated to horseradish peroxidase. Subsequent enzymic conversion of the substrate resulted in distinct absorbance differences when assaying milk samples containing Psychrotrophic Bacteria in the range 10(5) to 10(9) CFU ml(-1) . The detection threshold for the ELISA assay developed in this work is 10(5) CFU ml(-1).
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Detection of Psychrotrophic Bacteria on meat surfaces by an indirect ELISA using polyclonal antibodies against live cells of Pseudomonas fluorescens
Archiv Fur Lebensmittelhygiene, 1996Co-Authors: Isabel González, Teresa García, Bernabé Sanz, Rosario Martín, Paloma Morales, Pablo E. HernándezAbstract:Polyclonal antibodies raised against live cells of Pseudomonas (Ps.) fluorescens AH-70 have been used in an indirect enzyme-linked immunosorbent assay (ELISA) for detection of Ps. fluorescens and related Psychrotrophic Bacteria in refrigerated meat. These anti-live cells antibodies were recovered from the crude antiserum by ammonium sulfate precipitation and conjugated to biotin. Commercial ExtrAvidin-peroxidase conjugate was used to detect the biotinylated antibodies bound to their specific antigens. Subsequent enzymatic conversion of substrate gave distinct absorbance differences when assaying meat samples containing Ps. fluorescens strains of different origin as well as related Psychrotrophic microorganisms. The detection threshold for the ELISA assay developed in this work was 10 4 to 10 5 cfu/cm 2 .
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Polyclonal antibodies against protein F from the cell envelope of Pseudomonas fluorescens for the detection of Psychrotrophic Bacteria in refrigerated meat using an indirect ELISA.
Meat science, 1996Co-Authors: Isabel González, Teresa García, Bernabé Sanz, Rosario Martín, Paloma Morales, Pablo E. HernándezAbstract:Abstract An indirect enzyme-linked immunosorbent assay (ELISA) has been developed for detection of Pseudomonas fluorescens and related Psychrotrophic Bacteria in refrigerated meat. The ELISA uses polyclonal antibodies raised in rabbits against protein F from the cell envelope of Pseudomonas fluorescens AH-70. The anti-protein F antibodies were recovered from the crude antiserum by ammonium sulfate precipitation and conjugated to biotin. Commercial Extr Avidin-peroxidase conjugate was used to detect the biotinylated antibodies bound to their specific antigens. Subsequent enzymatic conversion of substrate gave distinct absorbance differences when assaying meat samples containing P. fluorescens strains of different origin as well as related Psychrotrophic microorganisms. The detection threshold for the ELISA assay developed in this work was 10 4 –10 5 cfu cm −2 .
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Detection of Pseudomonas fluorescens and Related Psychrotrophic Bacteria in Refrigerated Meat by a Sandwich ELISA.
Journal of food protection, 1994Co-Authors: Isabel González, Teresa García, Bernabé Sanz, Rosario Martín, Paloma Morales, Pablo E. HernándezAbstract:A sandwich enzyme-linked immunosorbent assay (ELISA) was developed for detection of Pseudomonas fluorescens and related Psychrotrophic Bacteria in refrigerated meat. Polyclonal antibodies were raised in rabbits against protein F from the cell envelope of P. fluorescens AH-70. The ELISA involved capturing antigens from the microorganisms present on meat samples with the anti-protein F antibodies immovilized on 96-well plates, and detecting bound antigens with the same anti-PF antibodies conjugated to biotin. Commercial ExtrAvidin-peroxidase conjugate was used to detect the biotinylated antibodies bound to their specific antigens. Subsequent enzymatic conversion of substrate gave distinct absorbance differences when assaying meat samples containing P. fluorescens strains of different origin as well as related Psychrotrophic microorganisms. The detection threshold for the ELISA assay developed in this work is 105 CFU/cm2.
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A sandwich enzyme‐linked immunosorbent assay (ELISA) for detection of Pseudomcnas fluorescens and related Psychrotrophic Bacteria in refrigerated milk
The Journal of applied bacteriology, 1993Co-Authors: Isabel González, Teresa García, Bernabé Sanz, Rosario Martín, Paloma Morales, Pablo E. HernándezAbstract:I. GONZALEZ, R. MARTIN, T. GARCIA, P. MORALES, B. SANZ AND P.E. HERNANDEZ. 1993. A sandwich ELISA (enz***me-linked immunosorbent assay) was developed for detection of Pseudomonas fluorescens and related Psychrotrophic Bacteria in refrigerated milk. Polyclonal antibodies were raised in rabbits against protein F from the cell envelope of Pseudomonas fluorescens AH-70. The anti-protein F antibodies (anti-PF) bound to the wells of a microtitre plate were used to capture this protein from the micro-organisms on milk samples. Further immunorecognition of the captured antigen was attained with the same anti-PF antibodies conjugated to biotin. ExtrAvidin-peroxidase was used to detect the biotinylated antibodies bound to their specific antigens. Subsequent enzymic conversion of substrate gave clear absorbance differences when assaying milk samples containing Ps. fluorescens strains of different origin as well as related Psychrotrophic micro-organisms.
Lei Yuan - One of the best experts on this subject based on the ideXlab platform.
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interspecies interactions in dual species biofilms formed by Psychrotrophic Bacteria and the tolerance of sessile communities to disinfectants
Journal of Food Protection, 2020Co-Authors: Lei Yuan, Faizan A. Sadiq, N I Wang, Guoqing HeAbstract:ABSTRACT: Biofilms on the surface of food processing equipment act as potential reservoirs of microbial contamination. Bacterial interactions are believed to play key roles in both biofilm formation and antimicrobial tolerance. In this study, Aeromonas hydrophila, Chryseobacterium oncorhynchi, and Pseudomonas libanensis, which were previously isolated from Chinese raw milk samples, were selected to establish two dual-species biofilm models (P. libanensis plus A. hydrophila and P. libanensis plus C. oncorhynchi) on stainless steel at 7°C. Subsequently, three disinfectants, hydrogen peroxide (100 ppm), peracetic acid (100 ppm), and sodium hypochlorite (100 ppm), were used to treat the developed sessile communities for 10 min. Structural changes after exposure to disinfectants were analyzed with confocal laser scanning microscopy. The cell numbers of both A. hydrophila and C. oncorhynchi recovered from surfaces increased when grown as dual species biofilms with P. libanensis. Dual-species biofilms were more tolerant of disinfectants than were each single-species biofilm. Peracetic acid was the most effective disinfectant for removing biofilms, followed by hydrogen peroxide and sodium hypochlorite. The results expand the knowledge of mixed-species biofilms formed by Psychrotrophic Bacteria and will be helpful for developing effective strategies to eliminate Bacterial mixed-species biofilms.
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RNA sequencing reveals the involvement of quorum sensing in dairy spoilage caused by Psychrotrophic Bacteria
LWT, 2020Co-Authors: Lei Yuan, N I Wang, Faizan A. SadiqAbstract:Abstract Dairy spoilage caused by Psychrotrophic Bacteria has been reported to be regulated by acyl-homoserine-lactones (AHLs)-based quorum sensing (QS) system. However, the precise role of AHLs produced by Psychrotrophic Bacteria in dairy spoilage remains unclear. The aim of this study was to evaluate the effects of AHLs on dairy spoilage caused by Pseudomonas azotoformans and Serrita liquefaciens at the transcriptional level. The particle size and volatile compounds of milk were selected as spoilage indicators for investigating the involvement of AHLs in dairy spoilage. Furthermore, the in situ gene expressions of Psychrotrophic Bacteria in AHLs-treated milk during cold storage were explored by RNA sequencing for the first time. The results revealed that the milk particle size and content of acids in milk were increased by exogenous AHLs, which confirm the enhancing effect of AHLs on the quality deterioration of milk. Transcriptome analysis revealed that a number of core genes of strains were significantly differentially expressed when treated with exogenous AHLs, and QS coordinate the metabolic processes within tested strains. Most of genes involving in the Bacterial growth and metabolism, enzymes production, and stress response were up-regulated by exogenous AHLs. The results elucidate the potential involvement of AHLs in dairy spoilage caused by Psychrotrophic Bacteria. This would give clue for novel strategy of controlling microbial spoilage in dairy products.
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Insights into Psychrotrophic Bacteria in Raw Milk: A Review.
Journal of food protection, 2019Co-Authors: Lei Yuan, Faizan A. Sadiq, Mette Burmølle, N I WangAbstract:ABSTRACT Supply of high-quality dairy products is the goal of every dairy producer throughout the world. However, Psychrotrophic Bacteria in raw milk, generally comprising Bacterial species of the ...
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spoilage potential of Psychrotrophic Bacteria isolated from raw milk and the thermo stability of their enzymes
Journal of Zhejiang University-science B, 2018Co-Authors: Lei Yuan, Faizan A. Sadiq, Yang Li, Jingsi Gu, Huanyi Yang, Guoqing HeAbstract:The storage and transportation of raw milk at low temperatures promote the growth of Psychrotrophic Bacteria and the production of thermo-stable enzymes, which pose great threats to the quality and shelf-life of dairy products. Though many studies have been carried out on the spoilage potential of Psychrotrophic Bacteria and the thermo-stabilities of the enzymes they produce, further detailed studies are needed to devise an effective strategy to avoid dairy spoilage. The purpose of this study was to explore the spoilage potential of Psychrotrophic Bacteria from Chinese raw milk samples at both room temperature (28 °C) and refrigerated temperature (7 °C). Species of Yersinia, Pseudomonas, Serratia, and Chryseobacterium showed high proteolytic activity. The highest proteolytic activity was shown by Yersinia intermedia followed by Pseudomonas fluorescens (d). Lipolytic activity was high in isolates of Acinetobacter, and the highest in Acinetobacter guillouiae. Certain isolates showed positive β-galactosidase and phospholipase activity. Strains belonging to the same species sometimes showed markedly different phenotypic characteristics. Proteases and lipases produced by Psychrotrophic Bacteria retained activity after heat treatment at 70, 80, or 90 °C, and proteases appeared to be more heat-stable than lipases. For these reasons, thermo-stable spoilage enzymes produced by a high number of Psychrotrophic Bacterial isolates from raw milk are of major concern to the dairy industry. The results of this study provide valuable data about the spoilage potential of Bacterial strains in raw milk and the thermal resistance of the enzymes they produce.
