The influence of relative humidity (RH) on quasistatic current-voltage (I-V) characteristics of Bifidobacterium animalis subsp. lactis BB-12 thin layers was studied for the first time. The value of electrical conducti...The influence of relative humidity (RH) on quasistatic current-voltage (I-V) characteristics of Bifidobacterium animalis subsp. lactis BB-12 thin layers was studied for the first time. The value of electrical conductivity in 75% RH was found to be in the order of 10-7 (ohm·cm)-1, which was 106 orders of magnitude higher than that observed in dry atmosphere. It was concluded that RH played a key role in hysteresis behavior of the measured (I-V) characteristics. FTIR measurements showed that under water moisture environment, the associated bonds between amine and carboxyl group were greatly strengthened that was the source of free charge carries after ionization. The surface charge of Bifidobacterium animalis subsp. lactis BB-12 was found to be negative by zeta potential measurements, claiming that electrons were the charge carriers.展开更多
Raw goat milk cheeses are known for their natural microflora linked to many biodiversity factors such as the use of raw milk. That microflora serves probiotic attribution conferring a beneficial health impact on the c...Raw goat milk cheeses are known for their natural microflora linked to many biodiversity factors such as the use of raw milk. That microflora serves probiotic attribution conferring a beneficial health impact on the consumer. Darfiyeh is an artisanal raw goat milk cheese manufactured traditionally in Northern Lebanese Mountains. To emphasize its clinical significance in both digestive and immune system, and to provide health remunerations to the consumer, the cheese microbiota will be investigated. To serve that purpose, the presence of the two potent probiotic Lactic Acid Bacteria (LAB): Lactococcus lactis subsp. lactis and Lactobacillus plantarum will be investigated. For bacterial identification, selection and isolation: culture-dependent techniques that imply the use of laboratory media will be implemented, and culture independent techniques: Polymerase Chain Reaction (PCR) will be applied for further validation. Both bacteria were further verified as Lactococcus lactis subsp. lactis and Lactobacillus plantarum by implementing specie-specific primers for the qualitative PCR.展开更多
[Objective]In order to improve expression vector of L.lactis at food grade and widen application range of original system.[Method] Taking pNZ8149 as basis,the promoter PnisA of pNZ8149 was inserted L.lactis MG1363 and...[Objective]In order to improve expression vector of L.lactis at food grade and widen application range of original system.[Method] Taking pNZ8149 as basis,the promoter PnisA of pNZ8149 was inserted L.lactis MG1363 and SPusp45 of unknown secretory protein in downstream.Through PCR technology,specific primers were used to delete restriction sites between promoter sequence and signal peptide gene sequence and ensure better distance between SD sequence and start codon to construct secreting expression vector pNZS.The reporter gene gus was recombined into multiple cloning site of pNZS to construct pNZS-gus and L.lactis was transformed by electroporation.10 ng/ml nisin was used for induction culture,then culture solution was conducted GUS staining test.[Result]The new constructed L.lactis N3900/pNZS-gus system could express active GUS protein and GUS protein could be secreted out of cell.[Conclusion]The successful construction of this system lays foundation for secretion expression study of protein and oral vaccine research.展开更多
The autolysis and proteolysis are important features in the strains of L. lactis used in the manufacture of cheese. The autolytic and proteolytic activity of L. lactis has been linked with the development of flavor an...The autolysis and proteolysis are important features in the strains of L. lactis used in the manufacture of cheese. The autolytic and proteolytic activity of L. lactis has been linked with the development of flavor and texture in the cheese. On the other hand, there is a growing interest in new strains isolated from raw-milk cheeses and vegetables. These wild-strains have showed different features of industrial importance in comparison with those observed in commercial cultures. However, it still not clear if the autolytic and proteolytic properties of these wild-strains differ from the industrial strains. The objective of this work was to assess the autolytic and proteolytic activities of 21 strains of L. lactis isolated from diverse sources. The rates of autolysis and proteolysis observed in vitro were highly strain-dependent. The pH and the NaCl concentration in the media affected significantly the autolysis of L. lactis. The strains isolated from vegetable showed in general low and medium autolytic activity, whereas the strains isolated from raw-milk cheeses had medium to high autolytic activity. The strain with highest proteolytic activity was a strain isolated from corn leaves. Although still not clear how this strain acquired this pronounced characteristic.展开更多
Our objective is to solve the lactose malabsorption and intolerance of human beings by combining micro-ecology path with genetic engineering technique. Plasmid pMG36e was used to clone and express a β-galactosidase g...Our objective is to solve the lactose malabsorption and intolerance of human beings by combining micro-ecology path with genetic engineering technique. Plasmid pMG36e was used to clone and express a β-galactosidase gene from L. delbrueckü bulgaricus strain 1.1480 in the Lactococcus lactis subsp. cremoris MG1363 and Lactococcus lactis subsp. lactis IL1403. The recombinant plasmid was preserved and proliferated in Escherichia coli ( E. coli) JM109, and transformed into MG1363 and IL1403 by electroporation. The protein expression was studied. ( 1 ) The bifidobacterium culture medium ( BBL) was suitable for the growth of the strain 1.1480. (2) With 13 amino acids at the N-terminus from the vector, β-gal- actosidase fusion protein (which retained the enzyme activity) could be successfully expressed in E. coli JM109, MG1363 and IL1403, but the expression quantity was larger in the former than in the latter two. (3) The SD sequence designed could be successfully recognized by both the E. coli and the Lactococcus lactis, but the expression level of the non-fusion β-galac- tosidase protein was lower than that of the fusion protein in the same host. The β-galactosidase genetically engineered E. coli JM109 is a useful tool to produce this enzyme in vitro . The signal peptide of the usp45 protein from the Lactococcus lac- tis can be added before the promoter sequence to promote β-galactosidase secretion from Lactococcus lactis . The potential ap- plication of the β-galactosidase genetically engineered MG1363 and IL1403 to cure the lactose malabsorption and lactose in- tolerance in both health food and medicine is promising.展开更多
The citrate metabolism has been extensively studied in lactic acid bacteria (LAB) for its aroma compound production. Among the 4-carbon (C4) by-products obtained from citrate fermentation, diacetyl is one of the bette...The citrate metabolism has been extensively studied in lactic acid bacteria (LAB) for its aroma compound production. Among the 4-carbon (C4) by-products obtained from citrate fermentation, diacetyl is one of the better known products for its contribution to the buttery aroma of dairy products. A lot of documents deal with ways to improve diacetyl concentration in food matrices. Apart from these organoleptic advantages, in a microbial ecosystem, the citrate metabolism gives selective advantages to citrate positive microorganisms. Citrate metabolism allows the LAB to use another carbon source for their growth, withstand acidic conditions and generate a “proton motive force” (PMF). Moreover, the citrate/glucid co-metabolism leads to the fast release of organic compounds known for having bacteriostatic effects. Under specific conditions, the C4?pathway liberates diacetyl which is bacteriostatic. In this review we first describe the citrate metabolism and the enzymes involved in the two homo- and heterofermentative LABLc diacetylactisandLeuconostocspp. Moreover, the way to shift the metabolic pathway toward the production of aromatic compounds is discussed for both of these fermentative types of bacteria. Finally, the selective advantages of citrate metabolism for LAB in complex microbial ecosystems are delineated.展开更多
A randomized case control prospective method was adopted in this study in order to assess the health benefit associated with the Darfiyeh cheese, a traditional Lebanese raw goat milk cheese ripened in goat skin. 21 pa...A randomized case control prospective method was adopted in this study in order to assess the health benefit associated with the Darfiyeh cheese, a traditional Lebanese raw goat milk cheese ripened in goat skin. 21 participants were recruited and divided into 2 groups: test group (n = 10) and control group (n = 11). Venous blood and stools were collected at day 14, 21 and day 0 and 21 respectively. Flow cytometry was performed on blood sample. Fecal samples were plated on Plate Count Agar (PCA) and de Man, Rogosa and Sharpe Agar (MRS) agar in order to monitor any alteration in the gastrointestinal tract (GIT). At day 24, a significant increase by 27.67% (p = 0.043) in the bacterial count was seen on the MRS agar for the test group in comparison to no change in the total bacterial count. At day 14 a significant drop (p = 0.026) in CD3+/CD4+ population in the test group (35.67 vs 42.87), and a non-significant drop (p = 0.818) in CD8+ (24.76 vs 28.28) is seen when compared to control group. At day 24, no significant change (p = 0.20) in the CD3+/CD4+ population in comparison between both groups and no change in CD8+ or Geo means in both groups. In conclusion, an alteration in the GIT microflora could be hinted at by the lactobacilli bacterium, which was not reflected on the total bacterial count.展开更多
Clostridium sporogenes and Clostridium tepidium strains were detected in traditional Kashar cheese samples with late blowing characteristics.To control Clostridium spp.,in Kashar cheese,dairy originated Lactic Acid Ba...Clostridium sporogenes and Clostridium tepidium strains were detected in traditional Kashar cheese samples with late blowing characteristics.To control Clostridium spp.,in Kashar cheese,dairy originated Lactic Acid Bacteria(LAB)strains were tested under in vitro conditions and during Kashar production.Two strains,Lactiplantibacillus plantarum and Lactococcus lactis subsp.lactis demonstrated anticlostridial activity in vitro and the co-inoculum of these two strains(107 cfu g^(-1))were tested during the challenge test on Kashar cheese production in which a contamination ratio of 10^(4) cfu g^(-1) with spores of Cl.sporogenes were applied.Kashar samples were stored at 4℃ and 25℃ during 40 days of storage period and microbiological and physicochemical properties of Kashar samples were determined during this period.A decrement of nearly 1 log cfu g^(-1) in Cl.sporogenes numbers was observed in Kashar samples produced with co-inoculum of Lb.plantarum and L.lactis subsp.lactis stored at 4℃ but this was not the case for the Kashar samples stored at 25℃.This study revealed the potential of distinct LAB strains to control Cl.sporogenes spores in semi-hard cheese samples as biocontrol agents at 4℃ storage.展开更多
文摘The influence of relative humidity (RH) on quasistatic current-voltage (I-V) characteristics of Bifidobacterium animalis subsp. lactis BB-12 thin layers was studied for the first time. The value of electrical conductivity in 75% RH was found to be in the order of 10-7 (ohm·cm)-1, which was 106 orders of magnitude higher than that observed in dry atmosphere. It was concluded that RH played a key role in hysteresis behavior of the measured (I-V) characteristics. FTIR measurements showed that under water moisture environment, the associated bonds between amine and carboxyl group were greatly strengthened that was the source of free charge carries after ionization. The surface charge of Bifidobacterium animalis subsp. lactis BB-12 was found to be negative by zeta potential measurements, claiming that electrons were the charge carriers.
文摘Raw goat milk cheeses are known for their natural microflora linked to many biodiversity factors such as the use of raw milk. That microflora serves probiotic attribution conferring a beneficial health impact on the consumer. Darfiyeh is an artisanal raw goat milk cheese manufactured traditionally in Northern Lebanese Mountains. To emphasize its clinical significance in both digestive and immune system, and to provide health remunerations to the consumer, the cheese microbiota will be investigated. To serve that purpose, the presence of the two potent probiotic Lactic Acid Bacteria (LAB): Lactococcus lactis subsp. lactis and Lactobacillus plantarum will be investigated. For bacterial identification, selection and isolation: culture-dependent techniques that imply the use of laboratory media will be implemented, and culture independent techniques: Polymerase Chain Reaction (PCR) will be applied for further validation. Both bacteria were further verified as Lactococcus lactis subsp. lactis and Lactobacillus plantarum by implementing specie-specific primers for the qualitative PCR.
基金Supported by Doctoral Fund of Jilin Agricultural University(20070193005)~~
文摘[Objective]In order to improve expression vector of L.lactis at food grade and widen application range of original system.[Method] Taking pNZ8149 as basis,the promoter PnisA of pNZ8149 was inserted L.lactis MG1363 and SPusp45 of unknown secretory protein in downstream.Through PCR technology,specific primers were used to delete restriction sites between promoter sequence and signal peptide gene sequence and ensure better distance between SD sequence and start codon to construct secreting expression vector pNZS.The reporter gene gus was recombined into multiple cloning site of pNZS to construct pNZS-gus and L.lactis was transformed by electroporation.10 ng/ml nisin was used for induction culture,then culture solution was conducted GUS staining test.[Result]The new constructed L.lactis N3900/pNZS-gus system could express active GUS protein and GUS protein could be secreted out of cell.[Conclusion]The successful construction of this system lays foundation for secretion expression study of protein and oral vaccine research.
文摘The autolysis and proteolysis are important features in the strains of L. lactis used in the manufacture of cheese. The autolytic and proteolytic activity of L. lactis has been linked with the development of flavor and texture in the cheese. On the other hand, there is a growing interest in new strains isolated from raw-milk cheeses and vegetables. These wild-strains have showed different features of industrial importance in comparison with those observed in commercial cultures. However, it still not clear if the autolytic and proteolytic properties of these wild-strains differ from the industrial strains. The objective of this work was to assess the autolytic and proteolytic activities of 21 strains of L. lactis isolated from diverse sources. The rates of autolysis and proteolysis observed in vitro were highly strain-dependent. The pH and the NaCl concentration in the media affected significantly the autolysis of L. lactis. The strains isolated from vegetable showed in general low and medium autolytic activity, whereas the strains isolated from raw-milk cheeses had medium to high autolytic activity. The strain with highest proteolytic activity was a strain isolated from corn leaves. Although still not clear how this strain acquired this pronounced characteristic.
文摘Our objective is to solve the lactose malabsorption and intolerance of human beings by combining micro-ecology path with genetic engineering technique. Plasmid pMG36e was used to clone and express a β-galactosidase gene from L. delbrueckü bulgaricus strain 1.1480 in the Lactococcus lactis subsp. cremoris MG1363 and Lactococcus lactis subsp. lactis IL1403. The recombinant plasmid was preserved and proliferated in Escherichia coli ( E. coli) JM109, and transformed into MG1363 and IL1403 by electroporation. The protein expression was studied. ( 1 ) The bifidobacterium culture medium ( BBL) was suitable for the growth of the strain 1.1480. (2) With 13 amino acids at the N-terminus from the vector, β-gal- actosidase fusion protein (which retained the enzyme activity) could be successfully expressed in E. coli JM109, MG1363 and IL1403, but the expression quantity was larger in the former than in the latter two. (3) The SD sequence designed could be successfully recognized by both the E. coli and the Lactococcus lactis, but the expression level of the non-fusion β-galac- tosidase protein was lower than that of the fusion protein in the same host. The β-galactosidase genetically engineered E. coli JM109 is a useful tool to produce this enzyme in vitro . The signal peptide of the usp45 protein from the Lactococcus lac- tis can be added before the promoter sequence to promote β-galactosidase secretion from Lactococcus lactis . The potential ap- plication of the β-galactosidase genetically engineered MG1363 and IL1403 to cure the lactose malabsorption and lactose in- tolerance in both health food and medicine is promising.
文摘The citrate metabolism has been extensively studied in lactic acid bacteria (LAB) for its aroma compound production. Among the 4-carbon (C4) by-products obtained from citrate fermentation, diacetyl is one of the better known products for its contribution to the buttery aroma of dairy products. A lot of documents deal with ways to improve diacetyl concentration in food matrices. Apart from these organoleptic advantages, in a microbial ecosystem, the citrate metabolism gives selective advantages to citrate positive microorganisms. Citrate metabolism allows the LAB to use another carbon source for their growth, withstand acidic conditions and generate a “proton motive force” (PMF). Moreover, the citrate/glucid co-metabolism leads to the fast release of organic compounds known for having bacteriostatic effects. Under specific conditions, the C4?pathway liberates diacetyl which is bacteriostatic. In this review we first describe the citrate metabolism and the enzymes involved in the two homo- and heterofermentative LABLc diacetylactisandLeuconostocspp. Moreover, the way to shift the metabolic pathway toward the production of aromatic compounds is discussed for both of these fermentative types of bacteria. Finally, the selective advantages of citrate metabolism for LAB in complex microbial ecosystems are delineated.
文摘A randomized case control prospective method was adopted in this study in order to assess the health benefit associated with the Darfiyeh cheese, a traditional Lebanese raw goat milk cheese ripened in goat skin. 21 participants were recruited and divided into 2 groups: test group (n = 10) and control group (n = 11). Venous blood and stools were collected at day 14, 21 and day 0 and 21 respectively. Flow cytometry was performed on blood sample. Fecal samples were plated on Plate Count Agar (PCA) and de Man, Rogosa and Sharpe Agar (MRS) agar in order to monitor any alteration in the gastrointestinal tract (GIT). At day 24, a significant increase by 27.67% (p = 0.043) in the bacterial count was seen on the MRS agar for the test group in comparison to no change in the total bacterial count. At day 14 a significant drop (p = 0.026) in CD3+/CD4+ population in the test group (35.67 vs 42.87), and a non-significant drop (p = 0.818) in CD8+ (24.76 vs 28.28) is seen when compared to control group. At day 24, no significant change (p = 0.20) in the CD3+/CD4+ population in comparison between both groups and no change in CD8+ or Geo means in both groups. In conclusion, an alteration in the GIT microflora could be hinted at by the lactobacilli bacterium, which was not reflected on the total bacterial count.
基金Fatmanur Demirbas¸was supported by Turkish Council of Higher Education with 100/2000 PhD programme and by TUB˙ITAK with 2211-C programme.
文摘Clostridium sporogenes and Clostridium tepidium strains were detected in traditional Kashar cheese samples with late blowing characteristics.To control Clostridium spp.,in Kashar cheese,dairy originated Lactic Acid Bacteria(LAB)strains were tested under in vitro conditions and during Kashar production.Two strains,Lactiplantibacillus plantarum and Lactococcus lactis subsp.lactis demonstrated anticlostridial activity in vitro and the co-inoculum of these two strains(107 cfu g^(-1))were tested during the challenge test on Kashar cheese production in which a contamination ratio of 10^(4) cfu g^(-1) with spores of Cl.sporogenes were applied.Kashar samples were stored at 4℃ and 25℃ during 40 days of storage period and microbiological and physicochemical properties of Kashar samples were determined during this period.A decrement of nearly 1 log cfu g^(-1) in Cl.sporogenes numbers was observed in Kashar samples produced with co-inoculum of Lb.plantarum and L.lactis subsp.lactis stored at 4℃ but this was not the case for the Kashar samples stored at 25℃.This study revealed the potential of distinct LAB strains to control Cl.sporogenes spores in semi-hard cheese samples as biocontrol agents at 4℃ storage.
