Growth and osmotic response of Lactobacillus bulgaricus ATCC 11842 under hyperosmotic constraint were investigated in a chemically defined medium （CDM） and MRS medium. NaCl could inhibit the growth of L. bulgaricus ...Growth and osmotic response of Lactobacillus bulgaricus ATCC 11842 under hyperosmotic constraint were investigated in a chemically defined medium （CDM） and MRS medium. NaCl could inhibit the growth of L. bulgaricus which decreased with increasing NaCl concentration. In the MRS, NaCl of 1.0 mol·L-1 was the biggest salt stress concentration; in the CDM, 0.8 mol·L-1 was the biggest inhibition concentration. In contrast to what was observed in other lactic acid bacteria, proline, glycine betaine and related molecules were unable to relieve inhibition of growth of L. bulgaricus under osmotic constraint. This was correlated to the absence of sequences homologous to the genes coding for glycine-betaine and/or proline transporters described in Lactococcus lactis and Bacillus subtilis. The amino acid aspartate and alanine were proved to be osmoprotective under NaCl stress. Addition of peptone （0.25% w/v） in the presence of salt led to a stimulation of the growth, as the decrease of the lag time and generation time, and the final biomass increased from 0.31 to 0.64.展开更多
Predictive microbiology was utilized to model Staphylococcus aureus （S. aureus） growth and staphylococcal enterotoxin A （SEA） production in milk in this study. The modifed logistic model, modifed Gompertz model an...Predictive microbiology was utilized to model Staphylococcus aureus （S. aureus） growth and staphylococcal enterotoxin A （SEA） production in milk in this study. The modifed logistic model, modifed Gompertz model and Baranyi model were applied to model growth data of S. aureus between 15℃ and 37℃. Model comparisons indicated that Baranyi model described the growth data more accurately than two others with a mean square error of 0.0129. Growth rates generated from Baranyi model matched the observed ones with a bias factor of 0.999 and an accuracy factor of 1.01, and ft a square root model with respect to temperature; other two modifed models both overestimated the observed ones. SEA amount began to be detected when the cell number reached106.4 cfu ？ mL-1, and showed the linear correlation with time. Besides, the rate of SEA production ftted an exponential relationship as a function of temperature. Predictions based on the study could be applied to indicate possible growth of S. aureus and prevent the occurrence of staphylococcal food poisoning.展开更多
Human milk fat （HMF） is the component that supplies the highest fraction of the infant＇s required dietary energy. Other sources of fat are necessary and crucial for infants while the breastfeeding is not possible, ...Human milk fat （HMF） is the component that supplies the highest fraction of the infant＇s required dietary energy. Other sources of fat are necessary and crucial for infants while the breastfeeding is not possible, desirable or sufficient. There is enough scientific evidence that suggests the composition and distribution of the fatty acids affect the absorption of the fat in infants greatly, which influences the growth and health of infants. However, the composition and distribution of the fatty acids in certain fat such as cow milk fat or vegetable oil are different from those in human milk. So as to mimic human milk fat composition and structure, a series of human milk fat substitutes （HMFS） have been developed through enzymatic interesterification reaction during recent years This review described current trends in the production of HMFS, discussed the significance and methods of preparing HMFS and the problems and put forward potential solutions about this kind of product.展开更多
Drying technology of angiotensin converting enzyme （ACE） inhibitory peptides derived from bovine casein was investigated. No significance was observed on ACE inhibitory activity of products prepared by spay drying a...Drying technology of angiotensin converting enzyme （ACE） inhibitory peptides derived from bovine casein was investigated. No significance was observed on ACE inhibitory activity of products prepared by spay drying and freeze drying （P〉0.05）. Spay drying was the best drying process for practical industry production. The inlet temperature ranged from 140℃ to 160℃ and the exit temperature ranged from 70 ℃ to 90 ℃ during the spay drying process. Under the optimal conditions, scale-up of angiotensin converted enzyme inhibitory peptide from 1 L to 10 L and the experiment was successively conducted. Peptide yield was 29% and half inhibitory concentration （IC50） was 0.53 g. L^-1.展开更多
基金Supported by the National Natural Science Funds (31201397)Science Fund for Distinguished Young Scholars Program for Changjiang Scholars and Innovative Research Team in University (IRT0959)Doctor Start Fund of Northeast Agricultural University (2010RCB59)
文摘Growth and osmotic response of Lactobacillus bulgaricus ATCC 11842 under hyperosmotic constraint were investigated in a chemically defined medium （CDM） and MRS medium. NaCl could inhibit the growth of L. bulgaricus which decreased with increasing NaCl concentration. In the MRS, NaCl of 1.0 mol·L-1 was the biggest salt stress concentration; in the CDM, 0.8 mol·L-1 was the biggest inhibition concentration. In contrast to what was observed in other lactic acid bacteria, proline, glycine betaine and related molecules were unable to relieve inhibition of growth of L. bulgaricus under osmotic constraint. This was correlated to the absence of sequences homologous to the genes coding for glycine-betaine and/or proline transporters described in Lactococcus lactis and Bacillus subtilis. The amino acid aspartate and alanine were proved to be osmoprotective under NaCl stress. Addition of peptone （0.25% w/v） in the presence of salt led to a stimulation of the growth, as the decrease of the lag time and generation time, and the final biomass increased from 0.31 to 0.64.
基金Supported by"Academic Backbone"Project of Northeast Agricultural University(15XG26)the National High-level Talents Special Support Program of China
文摘Predictive microbiology was utilized to model Staphylococcus aureus （S. aureus） growth and staphylococcal enterotoxin A （SEA） production in milk in this study. The modifed logistic model, modifed Gompertz model and Baranyi model were applied to model growth data of S. aureus between 15℃ and 37℃. Model comparisons indicated that Baranyi model described the growth data more accurately than two others with a mean square error of 0.0129. Growth rates generated from Baranyi model matched the observed ones with a bias factor of 0.999 and an accuracy factor of 1.01, and ft a square root model with respect to temperature; other two modifed models both overestimated the observed ones. SEA amount began to be detected when the cell number reached106.4 cfu ？ mL-1, and showed the linear correlation with time. Besides, the rate of SEA production ftted an exponential relationship as a function of temperature. Predictions based on the study could be applied to indicate possible growth of S. aureus and prevent the occurrence of staphylococcal food poisoning.
基金Supported by Innovative Team of Developmental Science and Technology of Bio-dairy Products,Northeast AgriculturalUninversity (CXT007)
文摘Human milk fat （HMF） is the component that supplies the highest fraction of the infant＇s required dietary energy. Other sources of fat are necessary and crucial for infants while the breastfeeding is not possible, desirable or sufficient. There is enough scientific evidence that suggests the composition and distribution of the fatty acids affect the absorption of the fat in infants greatly, which influences the growth and health of infants. However, the composition and distribution of the fatty acids in certain fat such as cow milk fat or vegetable oil are different from those in human milk. So as to mimic human milk fat composition and structure, a series of human milk fat substitutes （HMFS） have been developed through enzymatic interesterification reaction during recent years This review described current trends in the production of HMFS, discussed the significance and methods of preparing HMFS and the problems and put forward potential solutions about this kind of product.
基金Supported by Scientific Research Foundation for Young Scholars of Heilongjiang Province of China (QC07C25)The National High Technology Research and Development Program of China (2008AA10Z315)
文摘Drying technology of angiotensin converting enzyme （ACE） inhibitory peptides derived from bovine casein was investigated. No significance was observed on ACE inhibitory activity of products prepared by spay drying and freeze drying （P〉0.05）. Spay drying was the best drying process for practical industry production. The inlet temperature ranged from 140℃ to 160℃ and the exit temperature ranged from 70 ℃ to 90 ℃ during the spay drying process. Under the optimal conditions, scale-up of angiotensin converted enzyme inhibitory peptide from 1 L to 10 L and the experiment was successively conducted. Peptide yield was 29% and half inhibitory concentration （IC50） was 0.53 g. L^-1.
