We examined the effect of linseed supplementation in finishing diet on intramuscular fat level and fatty acid composition of three bovine muscles （longissimus dorsi-LD, semitendinosus-ST, psoas major-PM）, total of s...We examined the effect of linseed supplementation in finishing diet on intramuscular fat level and fatty acid composition of three bovine muscles （longissimus dorsi-LD, semitendinosus-ST, psoas major-PM）, total of sixty-two young bulls, from six different genotypes Angus （A）, Charolais （CH）, Holstein-Friesian （H）, Hungarian Grey （HG）, Hungarian Simmental （HS）, Charolais x Hungarian Grey F1 （CHxHG）. The results showed that A bulls had the highest intramuscular fat （IM） level （3.76）, particularly in PM （4.74）, followed by HG （3.40）, crossbred HG （3.05）, CH （2.33）, HS （2.21）, with the lowest level for H （2.11） bulls. IMF for LD （2.87） and ST （1.77） muscles were significantly lower than PM （3.60） for all groups. SFA was significantly higher for PM than the other two, due to the high level oflM. The highest MUFA was detected in LD, significantly different from others. ST contained the highest PUFA （12.99）, followed by LD （10.30） and PM （10.19）. The n-6 fatty acids were affected either by breed, or by muscle type. The linoleic acid was the highest in muscle samples of Holstein bulls except for PM, while the lowest was in A bulls in all cases. The same tendency can be seen in all cases for long chain n-6 fatty acids. The overall mean of n-3 fatty acids varied among genotypes from 1.36 to 1.80%. The highest level was measured in ST of CH and H （2.19）, whereas the lowest one in LD of HG （1.22）. Significant differences among genotypes were shown only for PM. The level of n-3 series long chain fatty acids was the highest for ST, for LD and PM in H, CH and HS, respectively. The ratio of n-6/n-3 ranged from 4.48 to 6.22 and was significantly less favorable in H than in A bulls. The highest CLA level was detected in all cases in HG bulls.展开更多
Promoters are the most important tools to control and regulate the gene expression in synthetic biology and metabolic engineering. The expression of target genes in Escherichia coli is usually controlled by the high-s...Promoters are the most important tools to control and regulate the gene expression in synthetic biology and metabolic engineering. The expression of target genes in Escherichia coli is usually controlled by the high-strength inducible promoter with the result that the abnormally high transcription of these genes creates excessive metabolic load on the host, which decreases product formation. The constitutive expression systems are capable of avoiding these defects. In this study, to enrich the application of constitutive promoters in metabolic engineering, four promoters from the glycolytic pathway of E. coli were cloned and characterized using the enhanced green fluorescent protein as reporter. Among these promoters, Pgap Awas determined as the strongest one, the strength of which was about 8.92% of that of the widely used inducible promoter PT7. This promoter was used to control the expression of heterologous xylose reductase in E. coli for xylitol synthesis so as to verify its function in pathway engineering. The maximum xylitol titer(40.6 g·L-1) produced by engineered E. coli under the control of the constitutive promoter Pgap Awas obviously higher than that under the control of the inducible promoter PT7,indicating the feasibility and superiority of promoter Pgap Ain the metabolic engineering of E. coli.展开更多
An ideal surrogate host for heterologous production of various natural products is expected to have efficient nutrient utilization,fast growth,abundant precursors and energy supply,and a pronounced gene expression.Str...An ideal surrogate host for heterologous production of various natural products is expected to have efficient nutrient utilization,fast growth,abundant precursors and energy supply,and a pronounced gene expression.Streptomyces albus BK3-25 is a high-yield industrial strain producing type-Ⅰ polyketide sahnomycin,with a unique ability of bean oil utilization.Its potential of being a surrogate host for heterologous production of PKS was engineered and evaluated herein.Firstly,introduction of a three-gene cassette for the biosynthesis of ethylmalonyl-CoA resulted in accumulation of ethylmalonyl-CoA precursor and sahnomycin,and subsequent deletion of the sahnomycin biosynthetic gene cluster resulted in a host with rich supplies of common polyketide precursors,including malonyl-CoA,methylmalonyl-CoA,and ethylmalonyl-CoA.Secondly,the energy and reducing force were measured,and the improved accumulation of ATP and NADPH was observed in the mutant.Furthermore,the strength of a series of selected endogenous promoters based on microarray data was assessed at different growth phases,and a strong constitutive promoter was identified,providing a useful tool for further engineered gene expression.Finally,the potential of the BK3-25 derived host ZXJ-6 was evaluated with the introduction of the actinorhodin biosynthetic gene cluster from Streptomyces coelicolor,and the heterologous production of actinorhodin was obtained.This work clearly indicated the potential of the high-yield sahnomycin producer as a surrogate host for heterologous production of polyketides,although more genetic manipulation should be conducted to streamline its performance.展开更多
文摘We examined the effect of linseed supplementation in finishing diet on intramuscular fat level and fatty acid composition of three bovine muscles （longissimus dorsi-LD, semitendinosus-ST, psoas major-PM）, total of sixty-two young bulls, from six different genotypes Angus （A）, Charolais （CH）, Holstein-Friesian （H）, Hungarian Grey （HG）, Hungarian Simmental （HS）, Charolais x Hungarian Grey F1 （CHxHG）. The results showed that A bulls had the highest intramuscular fat （IM） level （3.76）, particularly in PM （4.74）, followed by HG （3.40）, crossbred HG （3.05）, CH （2.33）, HS （2.21）, with the lowest level for H （2.11） bulls. IMF for LD （2.87） and ST （1.77） muscles were significantly lower than PM （3.60） for all groups. SFA was significantly higher for PM than the other two, due to the high level oflM. The highest MUFA was detected in LD, significantly different from others. ST contained the highest PUFA （12.99）, followed by LD （10.30） and PM （10.19）. The n-6 fatty acids were affected either by breed, or by muscle type. The linoleic acid was the highest in muscle samples of Holstein bulls except for PM, while the lowest was in A bulls in all cases. The same tendency can be seen in all cases for long chain n-6 fatty acids. The overall mean of n-3 fatty acids varied among genotypes from 1.36 to 1.80%. The highest level was measured in ST of CH and H （2.19）, whereas the lowest one in LD of HG （1.22）. Significant differences among genotypes were shown only for PM. The level of n-3 series long chain fatty acids was the highest for ST, for LD and PM in H, CH and HS, respectively. The ratio of n-6/n-3 ranged from 4.48 to 6.22 and was significantly less favorable in H than in A bulls. The highest CLA level was detected in all cases in HG bulls.
基金Supported by the National High Technology Research and Development Program of China(863 Program)(2012AA02A704)the Major State Basic Research Development Program of China(973 Program)(2013CB733900)+1 种基金the National Natural Science Foundation of China(21176028,21376028)the National Research Foundation for the Doctoral Program of Higher Education of China(20121101110050)
文摘Promoters are the most important tools to control and regulate the gene expression in synthetic biology and metabolic engineering. The expression of target genes in Escherichia coli is usually controlled by the high-strength inducible promoter with the result that the abnormally high transcription of these genes creates excessive metabolic load on the host, which decreases product formation. The constitutive expression systems are capable of avoiding these defects. In this study, to enrich the application of constitutive promoters in metabolic engineering, four promoters from the glycolytic pathway of E. coli were cloned and characterized using the enhanced green fluorescent protein as reporter. Among these promoters, Pgap Awas determined as the strongest one, the strength of which was about 8.92% of that of the widely used inducible promoter PT7. This promoter was used to control the expression of heterologous xylose reductase in E. coli for xylitol synthesis so as to verify its function in pathway engineering. The maximum xylitol titer(40.6 g·L-1) produced by engineered E. coli under the control of the constitutive promoter Pgap Awas obviously higher than that under the control of the inducible promoter PT7,indicating the feasibility and superiority of promoter Pgap Ain the metabolic engineering of E. coli.
基金supported by grants from the National Natural Science Foundation of China(21661140002 and 31470157)the Ministry of Science and Technology of China(2012CB721005 and 2012AA022107)
文摘An ideal surrogate host for heterologous production of various natural products is expected to have efficient nutrient utilization,fast growth,abundant precursors and energy supply,and a pronounced gene expression.Streptomyces albus BK3-25 is a high-yield industrial strain producing type-Ⅰ polyketide sahnomycin,with a unique ability of bean oil utilization.Its potential of being a surrogate host for heterologous production of PKS was engineered and evaluated herein.Firstly,introduction of a three-gene cassette for the biosynthesis of ethylmalonyl-CoA resulted in accumulation of ethylmalonyl-CoA precursor and sahnomycin,and subsequent deletion of the sahnomycin biosynthetic gene cluster resulted in a host with rich supplies of common polyketide precursors,including malonyl-CoA,methylmalonyl-CoA,and ethylmalonyl-CoA.Secondly,the energy and reducing force were measured,and the improved accumulation of ATP and NADPH was observed in the mutant.Furthermore,the strength of a series of selected endogenous promoters based on microarray data was assessed at different growth phases,and a strong constitutive promoter was identified,providing a useful tool for further engineered gene expression.Finally,the potential of the BK3-25 derived host ZXJ-6 was evaluated with the introduction of the actinorhodin biosynthetic gene cluster from Streptomyces coelicolor,and the heterologous production of actinorhodin was obtained.This work clearly indicated the potential of the high-yield sahnomycin producer as a surrogate host for heterologous production of polyketides,although more genetic manipulation should be conducted to streamline its performance.
