为探究Levan型果聚糖对‘泰番3号’番茄生长和品质的影响,研究采用盆栽试验法,设试验组(复合肥+Levan型果聚糖)与对照组(仅复合肥),测定其叶片光合特性、果实重量、维生素C和番茄红素含量等指标。结果表明:试验组的净光合速率(Pn)和水...为探究Levan型果聚糖对‘泰番3号’番茄生长和品质的影响,研究采用盆栽试验法,设试验组(复合肥+Levan型果聚糖)与对照组(仅复合肥),测定其叶片光合特性、果实重量、维生素C和番茄红素含量等指标。结果表明:试验组的净光合速率(Pn)和水分利用效率(water use efficiency, WUE)显著高于对照组,分别提高了34.4%和373.1%;维生素C和番茄红素含量分别增加9.83%和12.61%,但单果重量和总产量无显著差异。以上结果说明,Levan型果聚糖可有效提升番茄光合能力、增强水分利用效率并改善果实营养品质,为其绿色高效栽培提供技术支撑。展开更多
Levan produced by Gluconobacter spp.has great potential in biotechnological applications.However,Gluconobacter spp.can synthesize organic acids during fermentation,resulting in environmental acidification.Few studies ...Levan produced by Gluconobacter spp.has great potential in biotechnological applications.However,Gluconobacter spp.can synthesize organic acids during fermentation,resulting in environmental acidification.Few studies have focused on the effects of environmental acidification on levan synthesis.This study revealed that the organic acids,mainly gluconic acid(GA)and 2-keto-gluconic acid(2KGA)secreted by Gluconobacter sp.MP2116 created a highly acidic environment(pH<3)that inhibited levan biosynthesis.The levansucrase derived from strain MP2116 had high enzyme activity at pH 4.0~pH 6.5.When the ambient pH was less than 3,the enzyme activity decreased by 67%.Knocking out the mgdh gene of membrane-bound glucose dehydrogenase(mGDH)in the GA and 2KGA synthesis pathway in strain MP2116 eliminated the inhibitory effect of high acid levels on levansucrase function.As a result,the levan yield increased from 7.4 g/l(wild-type)to 18.8 g/l(Δmgdh)during fermentation without pH control.This study provides a new strategy for improving levan production by preventing the inhibition of polysaccharide synthesis by environmental acidification.展开更多
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
文摘为探究Levan型果聚糖对‘泰番3号’番茄生长和品质的影响,研究采用盆栽试验法,设试验组(复合肥+Levan型果聚糖)与对照组(仅复合肥),测定其叶片光合特性、果实重量、维生素C和番茄红素含量等指标。结果表明:试验组的净光合速率(Pn)和水分利用效率(water use efficiency, WUE)显著高于对照组,分别提高了34.4%和373.1%;维生素C和番茄红素含量分别增加9.83%和12.61%,但单果重量和总产量无显著差异。以上结果说明,Levan型果聚糖可有效提升番茄光合能力、增强水分利用效率并改善果实营养品质,为其绿色高效栽培提供技术支撑。
基金supported by the Shandong Provincial Natural Science Foundation(ZR2023MC113)Taishan Scholar Construction Foundation of Shandong Province(tshw20130963).
文摘Levan produced by Gluconobacter spp.has great potential in biotechnological applications.However,Gluconobacter spp.can synthesize organic acids during fermentation,resulting in environmental acidification.Few studies have focused on the effects of environmental acidification on levan synthesis.This study revealed that the organic acids,mainly gluconic acid(GA)and 2-keto-gluconic acid(2KGA)secreted by Gluconobacter sp.MP2116 created a highly acidic environment(pH<3)that inhibited levan biosynthesis.The levansucrase derived from strain MP2116 had high enzyme activity at pH 4.0~pH 6.5.When the ambient pH was less than 3,the enzyme activity decreased by 67%.Knocking out the mgdh gene of membrane-bound glucose dehydrogenase(mGDH)in the GA and 2KGA synthesis pathway in strain MP2116 eliminated the inhibitory effect of high acid levels on levansucrase function.As a result,the levan yield increased from 7.4 g/l(wild-type)to 18.8 g/l(Δmgdh)during fermentation without pH control.This study provides a new strategy for improving levan production by preventing the inhibition of polysaccharide synthesis by environmental acidification.
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.
