Fermentation of bioflocculant with Corynebacterium glutamicum was studied by way of kinetic modeling.Lorentzian modified Logistic model, time-corrected Luedeking–Piret and Luedeking–Piret type models were proposed a...Fermentation of bioflocculant with Corynebacterium glutamicum was studied by way of kinetic modeling.Lorentzian modified Logistic model, time-corrected Luedeking–Piret and Luedeking–Piret type models were proposed and applied to describe the cell growth, bioflocculant synthesis and consumption of substrates, with the correlation of initial biomass concentration and initial glucose concentration, respectively. The results showed that these models could well characterize the batch culture process of C. glutamicum at various initial glucose concentrations from 10.0 to 17.5 g·L-1. The initial biomass concentration could shorten the lag time of cell growth,while the maximum biomass concentration was achieved only at the optimal initial glucose concentration of16.22 g·L-1. A novel three-stage fed-batch strategy for bioflocculant production was developed based on the model prediction, in which the lag phase, quick biomass growth and bioflocculant production stages were sequentially proceeded with the adjustment of glucose concentration and dissolved oxygen. Biomass of2.23 g·L-1was obtained and bioflocculant concentration was enhanced to 176.32 mg·L-1, 18.62% and403.63% higher than those in the batch process, respectively, indicating an efficient fed-batch culture strategy for bioflocculant production.展开更多
Fifty bacterial strains isolated from dairy product, skin and blood from cancer and kidney failure dialysis patients were identified to 22 species and the following genera： Brevibacterium, Corynebacterium, Arthrobact...Fifty bacterial strains isolated from dairy product, skin and blood from cancer and kidney failure dialysis patients were identified to 22 species and the following genera： Brevibacterium, Corynebacterium, Arthrobacter, Actinomyces, Exiguobacterium, Kocuria, Micrococcus, Rothia, Rhodococcus and classified numerically using a set of 52 phenetic characteristics, using simple matching coefficient （Ssm） and clustering method of unweighted average linkage between groups by SPSS program. They were also grouped to 7 main clusters and 29 sub-clusters in the hierarchical tree. Twelve isolates of the different species from the genera Brevibacterium, Arthrobacter, Corynebacterium, Kocuria, Rhodococcus, Rothia were selected from the taxonomic clusters and probed for lin gene by peR. One species Kocuria rhizophila which inhibited most of the test organism did not have lin gene in the chromosome while the species Corynebacterium glucuronolyticum, Arthrobacter comminsii, Arthrobacter oxydans have the lin gene. Our results establish a wide distribution of the structural gene encoding this Iinocin M 18 within coryneform bacteria and also in the genus Kocuria.展开更多
Rhodococcus equi, previously known as Corynebacterium equi, is one of the most important causes of zoonotic infections in grazing animals. Increased cases of human infection with R. equi have been reported, especially...Rhodococcus equi, previously known as Corynebacterium equi, is one of the most important causes of zoonotic infections in grazing animals. Increased cases of human infection with R. equi have been reported, especially in immunocompromised patients, within recent years. We present a case of R. equi bacteremia in a 51-year-old man with diabetes and liver cirrhosis, on long-term corticosteroid therapy after skin-grafting surgery. The patient recovered soon after he was treated with vancomycin. This review focuses on the microbiological characteristics of this organism, and the diagnosis and treatment of this infection.展开更多
The glycerol utilization (gyl) operon is involved in clavulanic acid (CA) production by Streptomyces clavuligerus, and possibly supplies the glyceraldehyde-3-phosphate (G3P) precursor for CA biosynthesis. The gyl oper...The glycerol utilization (gyl) operon is involved in clavulanic acid (CA) production by Streptomyces clavuligerus, and possibly supplies the glyceraldehyde-3-phosphate (G3P) precursor for CA biosynthesis. The gyl operon is regulated by GylR and is induced by glycerol. To enhance CA production in S. clavuligerus, an extra copy of ccaR expressed from Pgyl (the gyl promoter) was integrated into the chromosome of S. clavuligerus NRRL 3585. This construct coordinated the transcription of CA biosynthetic pathway genes with expression of the gyl operon. In the transformants carrying the Pgyl-controlled regulatory gene ccaR, CA production was enhanced 3.19-fold in glycerol-enriched batch cultures, relative to the control strain carrying an extra copy of ccaR controlled by its own promoter (PccaR). Consistent with enhanced CA production, the transcription levels of ccaR, ceas2 and claR were significantly up-regulated in the transformants containing Pgyl-controlled ccaR.展开更多
We developed a colorimetric assay to quantify clavulanic acid （CA） in culture broth of Streptomyces clavuligerus, to facilitate screening of a large number of S. clavuligerus mutants. The assay is based on a β-1act...We developed a colorimetric assay to quantify clavulanic acid （CA） in culture broth of Streptomyces clavuligerus, to facilitate screening of a large number of S. clavuligerus mutants. The assay is based on a β-1actamase-catalyzed reaction, in which the yellow substrate nitrocefin （λmax=390 nm） is converted to a red product （λmax=486 nm）. Since CA can irreversibly inhibit β-1actamase activity, the level of CA in a sample can be measured as a function of the A390]A486 ratio in the assay mixture. The sensitivity and detection window of the assay were determined to be 50 μg L -1 and 50 μg L to 10 mg L-1, respectively. The reliability of the assay was confirmed by comparing assay results with those obtained by HPLC. The assay was used to screen a pool of 65 S. clavuligerus mutants and was reliable for identifying CA over-producing mutants. Therefore, the assay saves time and labor in large-scale mutant screening and evaluation tasks. The detection window and the reliability of this assay are markedly better than those of previously reported CA assays. This assay method is suitable for high throughput screening of microbial samples and allows direct visual observation of CA levels on agar plates.展开更多
基金Supported by the National Natural Science Foundation of China(21206143,51378444)the program for New Century Excellent Talents of Education Ministry of China(ncet-13-0501)
文摘Fermentation of bioflocculant with Corynebacterium glutamicum was studied by way of kinetic modeling.Lorentzian modified Logistic model, time-corrected Luedeking–Piret and Luedeking–Piret type models were proposed and applied to describe the cell growth, bioflocculant synthesis and consumption of substrates, with the correlation of initial biomass concentration and initial glucose concentration, respectively. The results showed that these models could well characterize the batch culture process of C. glutamicum at various initial glucose concentrations from 10.0 to 17.5 g·L-1. The initial biomass concentration could shorten the lag time of cell growth,while the maximum biomass concentration was achieved only at the optimal initial glucose concentration of16.22 g·L-1. A novel three-stage fed-batch strategy for bioflocculant production was developed based on the model prediction, in which the lag phase, quick biomass growth and bioflocculant production stages were sequentially proceeded with the adjustment of glucose concentration and dissolved oxygen. Biomass of2.23 g·L-1was obtained and bioflocculant concentration was enhanced to 176.32 mg·L-1, 18.62% and403.63% higher than those in the batch process, respectively, indicating an efficient fed-batch culture strategy for bioflocculant production.
文摘Fifty bacterial strains isolated from dairy product, skin and blood from cancer and kidney failure dialysis patients were identified to 22 species and the following genera： Brevibacterium, Corynebacterium, Arthrobacter, Actinomyces, Exiguobacterium, Kocuria, Micrococcus, Rothia, Rhodococcus and classified numerically using a set of 52 phenetic characteristics, using simple matching coefficient （Ssm） and clustering method of unweighted average linkage between groups by SPSS program. They were also grouped to 7 main clusters and 29 sub-clusters in the hierarchical tree. Twelve isolates of the different species from the genera Brevibacterium, Arthrobacter, Corynebacterium, Kocuria, Rhodococcus, Rothia were selected from the taxonomic clusters and probed for lin gene by peR. One species Kocuria rhizophila which inhibited most of the test organism did not have lin gene in the chromosome while the species Corynebacterium glucuronolyticum, Arthrobacter comminsii, Arthrobacter oxydans have the lin gene. Our results establish a wide distribution of the structural gene encoding this Iinocin M 18 within coryneform bacteria and also in the genus Kocuria.
基金Project supported by the National Natural Science Foundation of China (No. 30871130)the Youth Talent Special Fund of the Health Bureau of Zhejiang Province, China (No. 2008QN016)
文摘Rhodococcus equi, previously known as Corynebacterium equi, is one of the most important causes of zoonotic infections in grazing animals. Increased cases of human infection with R. equi have been reported, especially in immunocompromised patients, within recent years. We present a case of R. equi bacteremia in a 51-year-old man with diabetes and liver cirrhosis, on long-term corticosteroid therapy after skin-grafting surgery. The patient recovered soon after he was treated with vancomycin. This review focuses on the microbiological characteristics of this organism, and the diagnosis and treatment of this infection.
基金supported by grants from the Ministry of Science and Technology of China (2009CB118905)
文摘The glycerol utilization (gyl) operon is involved in clavulanic acid (CA) production by Streptomyces clavuligerus, and possibly supplies the glyceraldehyde-3-phosphate (G3P) precursor for CA biosynthesis. The gyl operon is regulated by GylR and is induced by glycerol. To enhance CA production in S. clavuligerus, an extra copy of ccaR expressed from Pgyl (the gyl promoter) was integrated into the chromosome of S. clavuligerus NRRL 3585. This construct coordinated the transcription of CA biosynthetic pathway genes with expression of the gyl operon. In the transformants carrying the Pgyl-controlled regulatory gene ccaR, CA production was enhanced 3.19-fold in glycerol-enriched batch cultures, relative to the control strain carrying an extra copy of ccaR controlled by its own promoter (PccaR). Consistent with enhanced CA production, the transcription levels of ccaR, ceas2 and claR were significantly up-regulated in the transformants containing Pgyl-controlled ccaR.
基金supported by the Young Scientists Fund (Grant No. 31000025) from the National Natural Science Foundation of ChinaNational High Technology Research and Development Program of China (Grant No. 2012AA021302)
文摘We developed a colorimetric assay to quantify clavulanic acid （CA） in culture broth of Streptomyces clavuligerus, to facilitate screening of a large number of S. clavuligerus mutants. The assay is based on a β-1actamase-catalyzed reaction, in which the yellow substrate nitrocefin （λmax=390 nm） is converted to a red product （λmax=486 nm）. Since CA can irreversibly inhibit β-1actamase activity, the level of CA in a sample can be measured as a function of the A390]A486 ratio in the assay mixture. The sensitivity and detection window of the assay were determined to be 50 μg L -1 and 50 μg L to 10 mg L-1, respectively. The reliability of the assay was confirmed by comparing assay results with those obtained by HPLC. The assay was used to screen a pool of 65 S. clavuligerus mutants and was reliable for identifying CA over-producing mutants. Therefore, the assay saves time and labor in large-scale mutant screening and evaluation tasks. The detection window and the reliability of this assay are markedly better than those of previously reported CA assays. This assay method is suitable for high throughput screening of microbial samples and allows direct visual observation of CA levels on agar plates.
