Current research is concerned with the stability of stochastic logistic equation with Ornstein-Uhlenbeck process. First, this research proves that the stochastic logistic model with Ornstein-Uhlenbeck process has a po...Current research is concerned with the stability of stochastic logistic equation with Ornstein-Uhlenbeck process. First, this research proves that the stochastic logistic model with Ornstein-Uhlenbeck process has a positive solution. After that, it also introduces the sufficient conditions for stochastically stability of stochastic logistic model for cell growth of microorganism in fermentation process for positive equilibrium point by using Lyapunov function. In addition, this research establishes the sufficient conditions for zero solution as mentioned in Appendix A due to the cell growth of microorganism μmax, which cannot be negative in fermentation process. Furthermore, for numerical simulation, current research uses the 4-stage stochastic Runge-Kutta (SRK4) method to show the reality of the results.展开更多
In dairy and food industries lactic acid bacteria （LAB） have been used in form of starter culture that plays vital role in fermentation; as flavouring and texturizing or as preservative agents. There is increasing e...In dairy and food industries lactic acid bacteria （LAB） have been used in form of starter culture that plays vital role in fermentation; as flavouring and texturizing or as preservative agents. There is increasing evidence that lactobacilli which inhabit the gastrointestinal tract develop antimicrobial activities and participate in the host＇s defence system[1]. During fermentation, most of the LAB produces a number of different compounds like organic acids, hydrogen peroxide, diacetyl, acetaldehyde, carbon dioxide, polysaccharides, and proteinaceous compounds called bacteriocins or bacteriocinogenic peptides.展开更多
The rheological properties of wheat flour are very important for the production of bakery products,and the milling methods greatly influence the rheological properties.In this paper,we measured the particle size distr...The rheological properties of wheat flour are very important for the production of bakery products,and the milling methods greatly influence the rheological properties.In this paper,we measured the particle size distributions,damaged starch contents,granular morphology,and pasting properties of the wheat flour,also carried out the uniaxial elongation test,the texture profile analysis,and rheological properties of the dough to evaluate effects of two milling methods,i.e.impact mill(IM)and hammer mill(HM),on the rheological properties of wheat flour and dough.The results showed that milling methods had no significant effects on flour pasting temperature(except the flour H3 obtained by HM grinding three times)and springiness of dough.Flour samples milled by IM had a lower damaged starch content,higher trough viscosity,higher final viscosity and higher values of setback compared to samples processed by HM.After repeated milling of IM,the damaged starch content of the endosperm granules could be controlled below 1%(P<0.05).There was a gap between H1 and H2 in the elastic modulus value of the non-fermented dough group,and the difference increased after fermentation,which was more obvious in the values of viscosity modulus.The more the milling times,the greater the elastic and viscosity modulus of dough of flour processed by both IM and HM.展开更多
The objective of the present study was to examine the effect of different weaning methods on the ruminal methanogenic archaea composition and diversity in Holstein calves.Thirty-six newborn Holstein bull calves were a...The objective of the present study was to examine the effect of different weaning methods on the ruminal methanogenic archaea composition and diversity in Holstein calves.Thirty-six newborn Holstein bull calves were assigned to 1 of 3 treatments:(1)conventional weaning(d 56)and fed a high proportion of solid feed(CWS);(2)conventional weaning(d 56)and fed a high proportion of liquid feed(CWL);(3)early weaning(d 42)and fed with a high proportion of solid feed(EWS).High-throughput sequencing of the methyl coenzyme M reductase(mcr A)gene,which encodes theα-subunit of methyl coenzyme M reductase-the enzyme that catalyzes the final step in methanogenesis was used to determine the composition and diversity of rumen methanogens.No significant difference(P>0.05)was observed for operational taxonomic units(OTUs)or richness indices,but diversity indices increased(P<0.05)for calves fed high dietary solids.Predominant families across the three treatments were Methanobacteriaceae,Thermoplasmataceae and Methanomassiliicoccaceae.Calves in the EWS treatment had a higher(P<0.05)relative abundance of Methanobrevibacter sp.strain AbM4 and Methanosphaera stadtmanae,while calves in the CWL treatment had a higher(P<0.05)abundance of Methanosphaera sp.strain SM9.A positive(P<0.05)relationship was identified between butyrate and Methanobrevibacter sp.strain AbM4.In conclusion,the composition and diversity of methanogens in the rumen of Holstein calves varied under the different weaning methods.This study identified a positive relationship between butyrate and Methanobrevibacter sp.strain AbM4,potentially reflecting correlations between ruminal fermentation variables and methanogenesis function.These in-depth analyses provide further understanding of weaning methods for intensified production systems.展开更多
Scientifically sound methods to rapidly measure fecal indicator bacteria are important to ensure safe water for drinking and recreational purposes.A total of 200 water samples obtained from the Three Gorges Reservoir ...Scientifically sound methods to rapidly measure fecal indicator bacteria are important to ensure safe water for drinking and recreational purposes.A total of 200 water samples obtained from the Three Gorges Reservoir during three successive one-year study periods（October 2009 to September 2012） were analyzed using multiple-tube fermentation（MTF）and most probable numbers combined with polymerase chain reaction（MPN-PCR）.The MPN-PCR method was found to be significantly more sensitive than the MTF method for detecting Escherichia coli and Enterococcus spp.,and of equal sensitivity for detecting total coliforms when all surface water samples were grouped together.The two analytical methods had a strong,significant relationship,but MPN-PCR took only 12-18 hr,compared with the 3-8 days needed using the MTF method.Bacterial concentrations varied per sampling site but were significantly lower in the mainstream of the Yangtze River than those in the backwater areas of tributaries.The water quality of 85.8% of water samples from the mainstream was suitable for use as a centralized potable water source,while the water quality of 52.5% of water samples from the backwater areas was unsuitable for recreational activities.Relationships between fecal indicator bacteria showed significant correlation（r = 0.636-0.909,p 〈 0.01,n = 200）,while a weak but significant correlation was found between fecal indicators and water turbidity,water temperature,daily inflow,and total dissolved solids（r = 0.237-0.532,p 〈 0.05,n = 200）.The study indicated that MPN-PCR is a rapid and easily performed deoxyribonucleic acid（DNA）-based method for quantitative detection of viable total coliforms,E.coli,and Enterococcus spp.in surface water.展开更多
为提高海洋来源成团泛菌(Pantoea agglomerans)Y-03产低温甾醇酯酶的酶活力,该研究首先通过单因素试验及Plackett-Burman(PB)试验确定成团泛菌Y-03产低温甾醇酯酶酶活的显著影响因素,然后运用Box-Behnken(BB)响应面试验对其发酵工艺进...为提高海洋来源成团泛菌(Pantoea agglomerans)Y-03产低温甾醇酯酶的酶活力,该研究首先通过单因素试验及Plackett-Burman(PB)试验确定成团泛菌Y-03产低温甾醇酯酶酶活的显著影响因素,然后运用Box-Behnken(BB)响应面试验对其发酵工艺进行优化。结果表明,成团泛菌Y-03产低温甾醇酯酶的最适发酵工艺为葡萄糖添加量3.7%、胰蛋白胨添加量1.3%、K_(2)HPO_(4)添加量0.4%、初始p H值8、转速180 r/min、接种量4%、装液量44 m L/250 m L、发酵温度27℃。在此优化条件下,甾醇酯酶活力为484.24 U/L,相比于优化前酶活力提高143.89%。该研究为提高成团泛菌的甾醇酯酶产量及酶活力和未来放大生产研究奠定了基础。展开更多
文摘Current research is concerned with the stability of stochastic logistic equation with Ornstein-Uhlenbeck process. First, this research proves that the stochastic logistic model with Ornstein-Uhlenbeck process has a positive solution. After that, it also introduces the sufficient conditions for stochastically stability of stochastic logistic model for cell growth of microorganism in fermentation process for positive equilibrium point by using Lyapunov function. In addition, this research establishes the sufficient conditions for zero solution as mentioned in Appendix A due to the cell growth of microorganism μmax, which cannot be negative in fermentation process. Furthermore, for numerical simulation, current research uses the 4-stage stochastic Runge-Kutta (SRK4) method to show the reality of the results.
文摘In dairy and food industries lactic acid bacteria （LAB） have been used in form of starter culture that plays vital role in fermentation; as flavouring and texturizing or as preservative agents. There is increasing evidence that lactobacilli which inhabit the gastrointestinal tract develop antimicrobial activities and participate in the host＇s defence system[1]. During fermentation, most of the LAB produces a number of different compounds like organic acids, hydrogen peroxide, diacetyl, acetaldehyde, carbon dioxide, polysaccharides, and proteinaceous compounds called bacteriocins or bacteriocinogenic peptides.
基金the National Natural Science Foundation of China(No.31571873)the National Key Research and Development Program(2018YFD0401001)。
文摘The rheological properties of wheat flour are very important for the production of bakery products,and the milling methods greatly influence the rheological properties.In this paper,we measured the particle size distributions,damaged starch contents,granular morphology,and pasting properties of the wheat flour,also carried out the uniaxial elongation test,the texture profile analysis,and rheological properties of the dough to evaluate effects of two milling methods,i.e.impact mill(IM)and hammer mill(HM),on the rheological properties of wheat flour and dough.The results showed that milling methods had no significant effects on flour pasting temperature(except the flour H3 obtained by HM grinding three times)and springiness of dough.Flour samples milled by IM had a lower damaged starch content,higher trough viscosity,higher final viscosity and higher values of setback compared to samples processed by HM.After repeated milling of IM,the damaged starch content of the endosperm granules could be controlled below 1%(P<0.05).There was a gap between H1 and H2 in the elastic modulus value of the non-fermented dough group,and the difference increased after fermentation,which was more obvious in the values of viscosity modulus.The more the milling times,the greater the elastic and viscosity modulus of dough of flour processed by both IM and HM.
基金supported by the Key Program for International S&T Cooperation Projects of China(2016YFE0109000)the National Key R&D Program of China(2017YFF0211702)+1 种基金the National Natural Science Foundation of China(41475126 and 31802085)the Young Scientist Lifting Project,China(2017–2019)
文摘The objective of the present study was to examine the effect of different weaning methods on the ruminal methanogenic archaea composition and diversity in Holstein calves.Thirty-six newborn Holstein bull calves were assigned to 1 of 3 treatments:(1)conventional weaning(d 56)and fed a high proportion of solid feed(CWS);(2)conventional weaning(d 56)and fed a high proportion of liquid feed(CWL);(3)early weaning(d 42)and fed with a high proportion of solid feed(EWS).High-throughput sequencing of the methyl coenzyme M reductase(mcr A)gene,which encodes theα-subunit of methyl coenzyme M reductase-the enzyme that catalyzes the final step in methanogenesis was used to determine the composition and diversity of rumen methanogens.No significant difference(P>0.05)was observed for operational taxonomic units(OTUs)or richness indices,but diversity indices increased(P<0.05)for calves fed high dietary solids.Predominant families across the three treatments were Methanobacteriaceae,Thermoplasmataceae and Methanomassiliicoccaceae.Calves in the EWS treatment had a higher(P<0.05)relative abundance of Methanobrevibacter sp.strain AbM4 and Methanosphaera stadtmanae,while calves in the CWL treatment had a higher(P<0.05)abundance of Methanosphaera sp.strain SM9.A positive(P<0.05)relationship was identified between butyrate and Methanobrevibacter sp.strain AbM4.In conclusion,the composition and diversity of methanogens in the rumen of Holstein calves varied under the different weaning methods.This study identified a positive relationship between butyrate and Methanobrevibacter sp.strain AbM4,potentially reflecting correlations between ruminal fermentation variables and methanogenesis function.These in-depth analyses provide further understanding of weaning methods for intensified production systems.
基金supported by the Basic and Advanced Research Project of Chongqing CSTC (No.cstc2013jcyj A20011)the Special Foundation for Scientific and Technological Talents of Wanzhou District of Chongqing Province,China
文摘Scientifically sound methods to rapidly measure fecal indicator bacteria are important to ensure safe water for drinking and recreational purposes.A total of 200 water samples obtained from the Three Gorges Reservoir during three successive one-year study periods（October 2009 to September 2012） were analyzed using multiple-tube fermentation（MTF）and most probable numbers combined with polymerase chain reaction（MPN-PCR）.The MPN-PCR method was found to be significantly more sensitive than the MTF method for detecting Escherichia coli and Enterococcus spp.,and of equal sensitivity for detecting total coliforms when all surface water samples were grouped together.The two analytical methods had a strong,significant relationship,but MPN-PCR took only 12-18 hr,compared with the 3-8 days needed using the MTF method.Bacterial concentrations varied per sampling site but were significantly lower in the mainstream of the Yangtze River than those in the backwater areas of tributaries.The water quality of 85.8% of water samples from the mainstream was suitable for use as a centralized potable water source,while the water quality of 52.5% of water samples from the backwater areas was unsuitable for recreational activities.Relationships between fecal indicator bacteria showed significant correlation（r = 0.636-0.909,p 〈 0.01,n = 200）,while a weak but significant correlation was found between fecal indicators and water turbidity,water temperature,daily inflow,and total dissolved solids（r = 0.237-0.532,p 〈 0.05,n = 200）.The study indicated that MPN-PCR is a rapid and easily performed deoxyribonucleic acid（DNA）-based method for quantitative detection of viable total coliforms,E.coli,and Enterococcus spp.in surface water.
文摘为提高海洋来源成团泛菌(Pantoea agglomerans)Y-03产低温甾醇酯酶的酶活力,该研究首先通过单因素试验及Plackett-Burman(PB)试验确定成团泛菌Y-03产低温甾醇酯酶酶活的显著影响因素,然后运用Box-Behnken(BB)响应面试验对其发酵工艺进行优化。结果表明,成团泛菌Y-03产低温甾醇酯酶的最适发酵工艺为葡萄糖添加量3.7%、胰蛋白胨添加量1.3%、K_(2)HPO_(4)添加量0.4%、初始p H值8、转速180 r/min、接种量4%、装液量44 m L/250 m L、发酵温度27℃。在此优化条件下,甾醇酯酶活力为484.24 U/L,相比于优化前酶活力提高143.89%。该研究为提高成团泛菌的甾醇酯酶产量及酶活力和未来放大生产研究奠定了基础。
