Kefir is a fermented milk product produced by kefir grains traditionally or lyophilized starter culture.Some quality characteristics of kefir produced at 22℃ and 30℃ using kefir grains after addition of microbial le...Kefir is a fermented milk product produced by kefir grains traditionally or lyophilized starter culture.Some quality characteristics of kefir produced at 22℃ and 30℃ using kefir grains after addition of microbial levan and pullulan were investigated for 14 days.Additionally,the survival of different Gram-positive and Gram-negative bacteria strains which were inoculated before and after fermentation were investigated during storage.The pH and titratable acidity were in the ranges of 4.67–4.39 and 1.10–0.87%,respectively.The highest exopolysaccharide values(458.3–465.3 mg/kg)were found in the samples produced with the addition of 1%(w/v)of microbial levan at 30℃.Yeast counts were in the ranges of 6.73–5.11 log CFU/mL while the lactobacilli and lactic streptococci counts were in the ranges of 9.64–7.91 and 9.64–8.69 log CFU/mL,respectively.The microbial polysaccharide addition did not show any significant differences in the enumeration of lactic acid bacteria in kefir(p>0.05).All Gram-positive and Gram-negative bacteria grew/survived during fermentation however Listeria monocytogenes was the most susceptible test bacterium to metabolites during storage.The highest reduction in the counts of L.monocytogenes was determined as 2.39 log units after 24 h of fermentation at 30℃ in the samples which were inoculated before fermentation and produced with the addition of pullulan.Kefir samples produced at 30℃ without polysaccharide addition were considered as the best with respect to appearance,taste,consistency and overall acceptability.展开更多
Levan is a fructose homopolymer obtained from both plants and microorganisms.Microbial levan is typically produced in a variety of molecular weights(MW).Previous studies have shown that different MW of levan exhibit d...Levan is a fructose homopolymer obtained from both plants and microorganisms.Microbial levan is typically produced in a variety of molecular weights(MW).Previous studies have shown that different MW of levan exhibit different biological activities.Though levan was reported for its immunomodulatory effect by increasing nitric oxide(NO)production in RAW264.7 macrophage cells,whether its MW can affect this activity remains unknown.In this study,the effect of different levan MW from Bacillus subtilis on its immunoregulatory properties was investigated.B.subtilis was cultivated using various cultivation parameters to obtain levan of different MW.Three weight average MW of levan,>8×10^(5) Da(M1),1.5×10^(4) Da(M2)and 3.7×10^(3) Da(M3),were selected to test for their effect on modulating NO levels in RAW264.7 cells.Our results showed that M2 increased NO production in a dose-dependent manner,and more effectively than that of M1 and M3.Consistent with these findings,M2 significantly stimulated inducible nitric oxide synthase(iNOS)and cyclooxygenase-2(COX2)protein expression,while less pronounced effects were observed in the cells treated with M1 and M3.Therefore,our results demonstrate that various MW of levan have varying effects on its immunoregulatory activities in RAW264.7 cells.Furthermore,our findings suggest that the size of levan should be taken into account when employing levan as one of the active ingredients in functional foods and immunomodulatory products.展开更多
文摘Kefir is a fermented milk product produced by kefir grains traditionally or lyophilized starter culture.Some quality characteristics of kefir produced at 22℃ and 30℃ using kefir grains after addition of microbial levan and pullulan were investigated for 14 days.Additionally,the survival of different Gram-positive and Gram-negative bacteria strains which were inoculated before and after fermentation were investigated during storage.The pH and titratable acidity were in the ranges of 4.67–4.39 and 1.10–0.87%,respectively.The highest exopolysaccharide values(458.3–465.3 mg/kg)were found in the samples produced with the addition of 1%(w/v)of microbial levan at 30℃.Yeast counts were in the ranges of 6.73–5.11 log CFU/mL while the lactobacilli and lactic streptococci counts were in the ranges of 9.64–7.91 and 9.64–8.69 log CFU/mL,respectively.The microbial polysaccharide addition did not show any significant differences in the enumeration of lactic acid bacteria in kefir(p>0.05).All Gram-positive and Gram-negative bacteria grew/survived during fermentation however Listeria monocytogenes was the most susceptible test bacterium to metabolites during storage.The highest reduction in the counts of L.monocytogenes was determined as 2.39 log units after 24 h of fermentation at 30℃ in the samples which were inoculated before fermentation and produced with the addition of pullulan.Kefir samples produced at 30℃ without polysaccharide addition were considered as the best with respect to appearance,taste,consistency and overall acceptability.
基金financially supported by the Research and Development Fund,Burapha University(Grant no.12/2562&10/2565)the Science Innovation Facility,Faculty of Science,Burapha University(SIF-IN-60300003)+2 种基金the Center of Excellence for Innovation in Chemistry(PERCH-CIC)the Commission on Higher Education,Ministry of Education,Thailandthe Scientific Instruments Center,School of Science,King Mongkut’s Institute of Technology Ladkrabang.
文摘Levan is a fructose homopolymer obtained from both plants and microorganisms.Microbial levan is typically produced in a variety of molecular weights(MW).Previous studies have shown that different MW of levan exhibit different biological activities.Though levan was reported for its immunomodulatory effect by increasing nitric oxide(NO)production in RAW264.7 macrophage cells,whether its MW can affect this activity remains unknown.In this study,the effect of different levan MW from Bacillus subtilis on its immunoregulatory properties was investigated.B.subtilis was cultivated using various cultivation parameters to obtain levan of different MW.Three weight average MW of levan,>8×10^(5) Da(M1),1.5×10^(4) Da(M2)and 3.7×10^(3) Da(M3),were selected to test for their effect on modulating NO levels in RAW264.7 cells.Our results showed that M2 increased NO production in a dose-dependent manner,and more effectively than that of M1 and M3.Consistent with these findings,M2 significantly stimulated inducible nitric oxide synthase(iNOS)and cyclooxygenase-2(COX2)protein expression,while less pronounced effects were observed in the cells treated with M1 and M3.Therefore,our results demonstrate that various MW of levan have varying effects on its immunoregulatory activities in RAW264.7 cells.Furthermore,our findings suggest that the size of levan should be taken into account when employing levan as one of the active ingredients in functional foods and immunomodulatory products.
