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排序方式: 共有129条查询结果,搜索用时 31 毫秒
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Gabriel de Souza Colombo Isis Viana Mendes Betúlia de Morais Souto Cristine Chaves Barreto Luana Assis Serra Eliane Ferreira Noronha Nádia Skorupa Parachin João Ricardo Moreira de Almeida Betania Ferraz Quirino 《Letters in applied microbiology》2022,74(6):941-948
The current climate crisis demands replacement of fossil energy sources with sustainable alternatives. In this scenario, second-generation bioethanol, a product of lignocellulosic biomass fermentation, represents a more sustainable alternative. However, Saccharomyces cerevisiae cannot metabolize pentoses, such as xylose, present as a major component of lignocellulosic biomass. Xylose isomerase (XI) is an enzyme that allows xylose consumption by yeasts, because it converts xylose into xylulose, which is further converted to ethanol by the pentose-phosphate pathway. Only a few XI were successfully expressed in S. cerevisiae strains. This work presents a new bacterial XI, named GR-XI 1, obtained from a Brazilian goat rumen metagenomic library. Phylogenetic analysis confirmed the bacterial origin of the gene, which is related to Firmicutes XIs. After codon optimization, this enzyme, renamed XySC1, was functionally expressed in S. cerevisiae, allowing growth in media with xylose as sole carbon source. Overexpression of XySC1 in S. cerevisiae allowed the recombinant strain to efficiently consume and metabolize xylose under aerobic conditions. 相似文献
123.
Sergio Balzano Dominique Marie Priscillia Gourvil Daniel Vaulot 《The ISME journal》2012,6(8):1480-1498
The composition of photosynthetic pico and nanoeukaryotes was investigated in the North East Pacific and the Arctic Ocean with special emphasis on the Beaufort Sea during the MALINA cruise in summer 2009. Photosynthetic populations were sorted using flow cytometry based on their size and pigment fluorescence. Diversity of the sorted photosynthetic eukaryotes was determined using terminal-restriction fragment length polymorphism analysis and cloning/sequencing of the 18S ribosomal RNA gene. Picoplankton was dominated by Mamiellophyceae, a class of small green algae previously included in the prasinophytes: in the North East Pacific, the contribution of an Arctic Micromonas ecotype increased steadily northward becoming the only taxon occurring at most stations throughout the Beaufort Sea. In contrast, nanoplankton was more diverse: North Pacific stations were dominated by Pseudo-nitzschia sp. whereas those in the Beaufort Sea were dominated by two distinct Chaetoceros species as well as by Chrysophyceae, Pelagophyceae and Chrysochromulina spp.. This study confirms the importance of Arctic Micromonas within picoplankton throughout the Beaufort Sea and demonstrates that the photosynthetic picoeukaryote community in the Arctic is much less diverse than at lower latitudes. Moreover, in contrast to what occurs in warmer waters, most of the key pico- and nanoplankton species found in the Beaufort Sea could be successfully established in culture. 相似文献
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Fabiano de A. Ximenes Fabiane Quirino de Paula Silveira Edivaldo Ximenes F. Filho 《Current microbiology》1996,33(2):71-77
Nine Trichoderma harzianum strains were screened for β-xylosidase activity when grown in solid-state cultures on media containing wheat bran as the
carbon source. All strains produced β-xylosidase activity, the most active being in extracts of cultures of T. harzianum strain 4. A β-xylosidase was purified by ammonium sulfate precipitation, ultrafiltration, gel filtration, and ion exchange
chromatography from solid-state cultures of T. harzianum strain C. Enzyme preparations yielded a single band when stained for protein following eletrophoresis. The molecular weight
value, calculated following SDS-PAGE, was determined to be 60 kDa. β-Xylosidase was most active at pH 4.0–4.5 and 70°C. This
enzyme had a K
m
value of 0.053 mM. The phenol-sulfuric acid method detected the presence of a small amount of carbohydrate in the purified
enzyme preparation. β-Xylosidase was active against some p-nitrophenylglycosides. The enzyme was inactive against xylan and PNPG. β-xylosidase activity was inhibited by xylose and
SDS. Iodoacetamide, dithiothreitol, gluconolactone, glucose, and mercuric chloride failed to inactivate this enzyme's activity.
A synergistic effect was observed when β-xylosidase from T. harzianum strain C and β-xylanase from Aspergillus fumigatus were incubated with pretreated arabinoxylan.
Received: 1 December 1995 / Accepted: 11 December 1995 相似文献
126.
Lai Q Avolio AW Manzia TM Agnes S Tisone G Berloco PB Rossi M 《The International journal of biological markers》2011,26(3):153-159
Background: Milan criteria (MC) represent the most commonly adopted criteria for the selection of patients with hepatocellular carcinoma (HCC) waiting for liver transplantation (LT). However, MC are exclusively based on morphological aspects. The aim of the present study was to evaluate pre-LT-detectable biological parameters, to compare them with morphological ones in terms of tumor recurrence prediction and patient survival. Methods: A cohort of 153 consecutive adult patients who underwent LT for HCC on cirrhosis from January 1999 to March 2009 was retrospectively analyzed. Results: HCC recurrence was observed in 12 patients (7.8%). At multivariate logistic regression analysis, serum alpha-fetoprotein (AFP) was the unique independent negative risk factor for the development of HCC recurrence (odds ratio 2.0, p=0.03). Adopting a cutoff value of 210 ng/mL, patients who presented serum AFP =210 ng/mL showed a 5-year survival rate of 23.3% versus 76.2% observed in patients with pre-LT serum AFP <210 ng/mL (log-rank test: <0.0001). Conclusions: In our experience, AFP was the strongest predictor of HCC recurrence, stronger than tumor morphology. AFP could ameliorate the selection of LT candidates. Further studies to evaluate the combination of morphological and biological criteria are needed. 相似文献
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Yofukuji Katia Yasuko Cardozo Ana Lúcia Paz Quirino Bárbara Angélio Aleixo Matheus Henrique Ferreira Fugi Rosemara 《Hydrobiologia》2021,848(4):913-927
Hydrobiologia - The diversity of aquatic macrophytes can offer different local conditions required to support an increased number of microhabitats, therefore resulting in diverse biotic... 相似文献