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排序方式: 共有680条查询结果,搜索用时 15 毫秒
61.
Reeves AR Brikun IA Cernota WH Leach BI Gonzalez MC Weber JM 《Journal of industrial microbiology & biotechnology》2006,33(7):600-609
In carbohydrate-based fermentations of Saccharopolyspora erythraea, a polar knockout of the methylmalonyl-CoA mutase (MCM) gene, mutB, improved erythromycin production an average of 126% (within the range of 102–153% for a 0.95 confidence interval). In oil-based fermentations, where erythromycin production by the wild-type strain averages 184% higher (141–236%, 0.95 CI) than in carbohydrate-based fermentations, the same polar knockout in mutB surprisingly reduced erythromycin production by 66% (53–76%, 0.95 CI). A metabolic model is proposed where in carbohydrate-based fermentations MCM acts as a drain on the methylmalonyl-CoA metabolite pool, and in oil-based fermentations, MCM acts in the reverse direction to fill the methylmalonyl-CoA pool. Therefore, the model explains, in part, how the well-known oil-based process improvement for erythromycin production operates at the biochemical level; furthermore, it illustrates how the mutB erythromycin strain improvement mutation operates at the genetic level in carbohydrate-based fermentations. 相似文献
62.
Characteristics of bacteria showing high denitrification activity in saline wastewater 总被引:1,自引:0,他引:1
Yoshie S Ogawa T Makino H Hirosawa H Tsuneda S Hirata A 《Letters in applied microbiology》2006,42(3):277-283
AIMS: Denitrification efficiency at 10% salinity was compared with that at 2% salinity. The characteristics of bacterial strains isolated from the denitrification system, where an improvement of denitrification efficiency was observed at a high salinity were investigated. METHODS AND RESULTS: Two continuous feeding denitrification systems for saline solutions of 2% and 10% salinity, were operated. Denitrification efficiency at 10% salinity was higher than that at 2% salinity. The bacterial strains were isolated using the trypticase soy agar (TSA) medium at 30 degrees C. The phylogenetic analysis of 16S rRNA gene sequences of isolates indicated that halophilic species were predominant at 10% salinity. CONCLUSIONS: The improvement of denitrification efficiency at a high salinity was demonstrated. The strains isolated from the denitrifying system with 10% salinity were halophilic bacteria, Halomonas sp. and Marinobacter sp., suggesting that these bacteria show a high denitrifying activity at 10% salinity. SIGNIFICANCE AND IMPACT OF THE STUDY: The long-term acclimated sludge used in this study resulted in high denitrification performance at a high salinity, indicating that the design of a high-performance denitrification system for saline wastewater will be possible. 相似文献
63.
A new functionally based kinetic model for enzymatic hydrolysis of pure cellulose by the Trichoderma cellulase system is presented. The model represents the actions of cellobiohydrolases I, cellobiohydrolase II, and endoglucanase I; and incorporates two measurable and physically interpretable substrate parameters: the degree of polymerization (DP) and the fraction of beta-glucosidic bonds accessible to cellulase, F(a) (Zhang and Lynd, 2004). Initial enzyme-limited reaction rates simulated by the model are consistent with several important behaviors reported in the literature, including the effects of substrate characteristics on exoglucanase and endoglucanase activities; the degree of endo/exoglucanase synergy; the endoglucanase partition coefficient on hydrolysis rates; and enzyme loading on relative reaction rates for different substrates. This is the first cellulase kinetic model involving a single set of kinetic parameters that is successfully applied to a variety of cellulosic substrates, and the first that describes more than one behavior associated with enzymatic hydrolysis. The model has potential utility for data accommodation and design of industrial processes, structuring, testing, and extending understanding of cellulase enzyme systems when experimental date are available, and providing guidance for functional design of cellulase systems at a molecular scale. Opportunities to further refine cellulase kinetic models are discussed, including parameters that would benefit from further study. 相似文献
64.
Advances in Arachis genomics for peanut improvement 总被引:3,自引:0,他引:3
Pandey MK Monyo E Ozias-Akins P Liang X Guimarães P Nigam SN Upadhyaya HD Janila P Zhang X Guo B Cook DR Bertioli DJ Michelmore R Varshney RK 《Biotechnology advances》2012,30(3):639-651
Peanut genomics is very challenging due to its inherent problem of genetic architecture. Blockage of gene flow from diploid wild relatives to the tetraploid; cultivated peanut, recent polyploidization combined with self pollination, and the narrow genetic base of the primary genepool have resulted in low genetic diversity that has remained a major bottleneck for genetic improvement of peanut. Harnessing the rich source of wild relatives has been negligible due to differences in ploidy level as well as genetic drag and undesirable alleles for low yield. Lack of appropriate genomic resources has severely hampered molecular breeding activities, and this crop remains among the less-studied crops. The last five years, however, have witnessed accelerated development of genomic resources such as development of molecular markers, genetic and physical maps, generation of expressed sequenced tags (ESTs), development of mutant resources, and functional genomics platforms that facilitate the identification of QTLs and discovery of genes associated with tolerance/resistance to abiotic and biotic stresses and agronomic traits. Molecular breeding has been initiated for several traits for development of superior genotypes. The genome or at least gene space sequence is expected to be available in near future and this will further accelerate use of biotechnological approaches for peanut improvement. 相似文献
65.
琥珀酸脱氢酶作用的实验是《生物化学》课程的重要实验之一。由于材料来源、成本、操作、结果等在实验教学中存在的问题,影响了该实验的效果和开出率。采用普通鸽子胸脯处肌肉作为实验材料,并对实验条件和程序进行优化,从而使教学取得了较好的效果,实验开出率也得以提高。 相似文献
66.
一种启动子克隆的改良Adaptor-PCR方法及在橡胶树上的应用实例 总被引:1,自引:0,他引:1
真核生物通过顺式作用元件和反式作用因子相互作用实现基因的转录调控,而启动子区域含有多种顺式元件,作为基因表达调控网络的枢纽控制着基因转录的起始与效率,一直是基因表达调控研究的重点[1]。本文提供了一种改良的基于Adaptor-PCR启动子克隆方法,改进了接头序列,设计了适合两步法PCR的接头引物。选取了25种限制性内切酶对橡胶树基因组DNA进行酶切,在所有酶切产物都平端化后,与改进的接头连接,成功构建了以Adaptor-PCR为基础的橡胶树基因启动子克隆文库,并利用此文库成功克隆了橡胶树6个蔗糖转运蛋白基因、1个转化酶基因和1个海藻糖合酶基因的启动子。本文研究结果为橡胶树基因启动子克隆提供了一个高效平台,也为其他生物基因启动子克隆提供了有益的参考。 相似文献
67.
68.
69.
Ives Bruno M. Efombagn Juan C. Motamayor Olivier Sounigo Albertus B. Eskes Salomon Nyassé Christian Cilas Ray Schnell Maria J. Manzanares-Dauleux Maria Kolesnikova-Allen 《Tree Genetics & Genomes》2008,4(4):821-831
The genetic diversity of 400 accessions collected in cacao farms, 95 GenBank, and 31 reference accessions was analyzed using
the 12 microsatellite markers. The GenBank and reference accessions were subdivided into 12 accession groups (AG) that belong
to the traditional cacao genetic groups (GG) Lower Amazon Forastero (LA), Upper Amazon Forastero (UA), Trinitario, and Criollo
(Cr). The 12-microsatellite loci revealed a total of 125 alleles, 113 of which were present in the farm accession group (FA).
The within and between group variation for all AGs accounted respectively for 81% and 19% of the total molecular variation.
The average F
is for the FA was 0.15 suggesting a moderate level of inbreeding. Significant differences for the level of gene diversity were
found between the farm (0.50), GenBank (0.42 to 0.62), and reference (0.10 to 0.60) AGs. Genetic differentiation among AGs
was variable with F
st values varying between 0.14 and 0.57 for the different AGs. Analysis using a Bayesian model-based method showed the existence
of a high level of admixture for the farm accessions group. The LA genes were most represented in the FA (54%), followed by
UA (33%) and Cr (7%). The genes of LA were also the most represented in the GenBank (48%), followed by UA (24%) and Cr (14%).
Only 14% and 6% of the genes of the GenBank and farm accessions, respectively, could not be attributed to any of the reference
GGs. The results suggest the predominating presence of LA genes in the Cameroon farm accessions and a high level of admixture,
with apparent presence of genes of more than three GGs in most accessions. The traditional Trinitario types appear to have
almost disappeared from farmers fields. The admixture must be the result of hybridization and recombination of these genes
from the different GGs in seed gardens and in farmers’ fields. The use of selected farm accessions will depend on the GG that
it belongs to and also on their level of heterozygosity. Further implications of the results for breeding and for introduction
of new germplasm into the Cameroon GenBank are discussed. 相似文献
70.
The contribution of distant hybridization with decaploid Agropyron elongatum to wheat improvement in China 总被引:1,自引:0,他引:1
Zhensheng Li Bin Li Yiping Tong 《遗传学报》2008,35(8):451-456
Wheat is a staple food crop in the world as well as in China. Because of the progress of wheat breeding and other agricultural sci-technologies, the wheat grain yield per unit area has increased more than five folds from 1952 to 2006 in China. The first part of this article briefly reviews the history of wheat breeding in China. Second, the establishment of "Triticum aestivum-Agropyron" distant hybridization system and its contribution to wheat production and breeding in China are summarized. Finally, the future challenges of wheat breeding are discussed, which include how to increase the utilization efficiencies of water, soil nutrient and light energy through breeding.As an example, our research progress on how to increase light use efficiency in wheat through breeding is introduced and discussed. 相似文献