排序方式: 共有91条查询结果,搜索用时 312 毫秒
71.
Cao H Mi L Ye Q Zang G Yan M Wang Y Zhang Y Li X Xu L Xiong J Ouyang P Ying H 《Bioresource technology》2011,102(2):1733-1739
A novel NADH-dependent dehydrogenases/reductases (SDRs) superfamily reductase (PsCRII) was isolated from Pichia stipitis. It produced ethyl (S)-4-chloro-3-hydroxybutanoate [(S)-CHBE] in greater than 99% enantiomeric excess. This enzyme was purified to homogeneity by ammonium sulfate precipitation followed by Q-Sepharose chromatography. Compared to similar known reductases producing (S)-CHBE, PsCR II was more suitable for production since the purified PsCRII preferred the inexpensive cofactor NADH to NADPH as the electron donor. Furthermore, the Km of PsCRII for ethyl 4-chloro-3-oxobutanoate (COBE) was 3.3 mM, and the corresponding Vmax was 224 μmol/mg protein/min. The catalytic efficiency is the highest value ever reported for NADH-dependent reductases from yeasts that produce CHBE with high enantioselectivity. In addition, this enzyme exhibited broad substrate specificity for several β-keto esters using NADH as the coenzyme. The properties of PsCRII with those of other carbonyl reductases from yeasts were also compared in this study. 相似文献
72.
73.
Yong Chen Tao Zhou Dong Liu An Li Songbo Xu Qingguo Liu Bingbing Li Hanjie Ying 《Biotechnology and Bioprocess Engineering》2013,18(2):234-241
Pretreated cotton towels were used as carriers to immobilize Clostridium acetobutylicum CGMCC 5234 cells for butanol or ABE production from glucose and xylose. Results showed that cell immobilization was a promising method to increase butanol concentration, yield and productivity regardless of the sugar sources compared with cell suspension. In this study, a high butanol concentration of 10.02 g/L with a yield of 0.20 g/g was obtained from 60 g/L xylose with 9.9 g/L residual xylose using immobilized cells compared with 8.48 g/L butanol and a yield of 0.141 g/g with 20.2 g/L residual xylose from 60 g/L xylose using suspended cells. In mixed-sugar fermentation (30 g/L glucose plus 30 g/L xylose), the immobilized cultures produced 11.1 g/L butanol with a yield of 0.190 g/g, which were 28.3% higher than with suspended cells (8.65 g/L) during which 30 g/L glucose was utilized completely using both immobilized and suspended cells while 3.46 and 13.1 g/L xylose maintained untilized for immobilized and suspended cells, respectively. Based on the results, we speculated that immobilized cells showed enhanced tolerance to butanol toxicity and the cultures preferred glucose to xylose during ABE fermentation. Moreover, the cultures showed obvious difference when grown between high initial concentrations of glucose and those of xylose. Repeated-batch fermentations from glucose with immobilized cells showed better long-term stability than from xylose. At last, the morphologies of free and immobilized cells adsorbed on pretreated cotton towels during the growth cycle were examined by SEM. 相似文献
74.
Hanjie Li Anne M. van der Leun Ido Yofe Yaniv Lubling Dikla Gelbard-Solodkin Alexander C.J. van Akkooi Marlous van den Braber Elisa A. Rozeman John B.A.G. Haanen Christian U. Blank Hugo M. Horlings Eyal David Yael Baran Akhiad Bercovich Aviezer Lifshitz Ton N. Schumacher Amos Tanay Ido Amit 《Cell》2019,176(4):775-789.e18
75.
糖鞘脂(glycosphingolipids,GSLs)广泛存在于各种生物细胞膜的磷脂双分子层中,在维持细胞膜稳定性、调节包括粘附、增殖、凋亡和识别等多种细胞过程方面发挥着重要作用,并参与细胞多种生命活动。除此之外,GSLs与细胞凋亡过程密切相关,肿瘤相关GSLs有望作为恶性肿瘤的诊断标志物和免疫治疗靶点,这些发现对研究细胞凋亡及肿瘤治疗的新方向具有重要意义。因此,本文综述了GSLs介导细胞凋亡及其影响肿瘤细胞发生、发展和转移的最新研究进展,并讨论了GSLs代谢途径及其在肿瘤治疗中的研究现状,以及基于GSLs的靶向治疗策略的发展前景。 相似文献
76.
Acetone–butanol–ethanol competitive sorption simulation from single,binary, and ternary systems in a fixed‐bed of KA‐I resin
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Wei Zhuang Hanjie Ying Renjie Li Qingshi Wen Lili Wang Jingwei Zhou Pengpeng Yang 《Biotechnology progress》2015,31(1):124-134
Separation of butanol based on sorption methodology from acetone–butanol–ethanol (ABE) fermentation broth has advantages in terms of biocompatibility and stability, as well as economy, and therefore gains much attention. In this work a chromatographic column model based on the solid film linear driving force approach and the competitive Langmuir isotherm equations was used to predict the competitive sorption behaviors of ABE single, binary, and ternary mixture. It was observed that the outlet concentration of weaker retained components exceeded the inlet concentration, which is an evidence of competitive adsorption. Butanol, the strongest retained component, could replace ethanol almost completely and also most of acetone. In the end of this work, the proposed model was validated by comparison of the experimental and predicted ABE ternary breakthrough curves using the real ABE fermentation broth as a feed solution. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 31:124–134, 2015 相似文献
77.
Liu D Chen Y Li A Xie J Xiong J Bai J Chen X Niu H Zhou T Ying H 《Bioprocess and biosystems engineering》2012,35(5):729-737
A whole-cell biocatalytic process for uridine 5′-monophosphate (UMP) production from orotic acid by Saccharomyces cerevisiae was developed. To rationally redistribute the metabolic flux between glycolysis and pentose phosphate pathway, statistical
methods were employed first to find out the critical factors in the process. NaH2PO4, MgCl2 and pH were found to be the important factors affecting UMP production significantly. The levels of these three factors required
for the maximum production of UMP were determined: NaH2PO4 22.1 g/L; MgCl2 2.55 g/L; pH 8.15. An enhancement of UMP production from 6.12 to 8.13 g/L was achieved. A significant redistribution of metabolic
fluxes was observed and the underlying mechanism was discussed. 相似文献
78.
Xiaodi Liang Lin Zhang Yufeng Wan Xinyang Yu Yiming Guo Xiaoping Chen Cheng Tan Tianle Huang Hanjie Shen Xianyun Chen Hongying Li Ke Lv Fei Sun Shanguang Chen Jinhu Guo 《PloS one》2012,7(10)
In spaceflight human circadian rhythms and sleep patterns are likely subject to change, which consequently disturbs human physiology, cognitive abilities and performance efficiency. However, the influence of microgravity on sleep and circadian clock as well as the underlying mechanisms remain largely unknown. Placing volunteers in a prone position, whereby their heads rest at an angle of −6° below horizontal, mimics the microgravity environment in orbital flight. Such positioning is termed head-down bed rest (HDBR). In this work, we analysed the influence of a 45-day HDBR on physiological diurnal rhythms. We examined urinary electrolyte and hormone excretion, and the results show a dramatic elevation of cortisol levels during HDBR and recovery. Increased diuresis, melatonin and testosterone were observed at certain periods during HDBR. In addition, we investigated the changes in urination and defecation frequencies and found that the rhythmicity of urinary frequency during lights-off during and after HDBR was higher than control. The grouped defecation frequency data exhibits rhythmicity before and during HDBR but not after HDBR. Together, these data demonstrate that HDBR can alter a number of physiological processes associated with diurnal rhythms. 相似文献
79.
Lin X Wu J Jin X Fan J Li R Wen Q Qian W Liu D Chen X Chen Y Xie J Bai J Ying H 《Biotechnology progress》2012,28(4):962-972
The traditional distillation method for recovery of butanol from fermentation broth is an energy-intensive process. Separation of butanol based on adsorption methodology has advantages in terms of biocompatibility and stability, as well as economy, and therefore gains much attention. However, the application of the commercial adsorbents in the integrated acetone-butanol-ethanol (ABE) fermentation process is restricted due to the low recovery (less than 85%) and the weak capability of enrichment in the eluent (3-4 times). In this study, we investigated the sorption properties of butanol onto three kinds of adsorbents with different polarities developed in our laboratory, that is, XD-41, H-511, and KA-I resin. The sorption behaviors of single component and ABE ternary mixtures presented in the fermentation broths on KA-I resin were investigated. KA-I resin had higher affinity for butanol than for acetone, ethanol, glucose, acetic acid, and butyric acid. Multicomponent ABE sorption on KA-I resin was modeled using a single site extended Langmuir isotherm model. In a desorption study, all the adsorbed components were desorbed in one bed volume of methanol, and the recovery of butanol from KA-I resin was 99.7%. The concentration of butanol in the eluent was increased by a factor of 6.13. In addition, KA-I resin was successfully regenerated by two bed volumes of water. Because of its quick sorption, high sorption capacity, low cost, and ease of desorption and regeneration, KA-I resin exhibits good potential for compatibility with future ABE fermentation coupled with in situ recovery product removal techniques. 相似文献
80.
J Cao X Chen H Ren J Zhang L Li Y Chen J Xiong J Bai H Ying 《World journal of microbiology & biotechnology》2012,28(1):121-127
The production of cyclic adenosine monophosphate (cAMP) by Arthrobacter sp. A302 was studied in a 5 L stirred tank fermentor under a range of pH values (6.5–8.0) and glucose feeding rates. In batch
fermentation under a controlled pH, the optimum pH for cell growth was 7.5 with dry cell density (X) of 11.43 g L, and the
optimum pH for cAMP accumulation was 7.0 with cAMP concentration of 7.41 g L. In order to achieve the high X and cAMP yield
simultaneously, a pH-shift control strategy was proposed based on kinetic analysis of specific cell growth rate (μ) and specific
cAMP formation rate (q
s
). In this method, pH was controlled to 7.0 for the first 30 h of fermentation, and then subsequently shifted to 7.5 and maintained
until the end of the process. Application of this approach significantly enhanced the cAMP concentration. Thereafter, cAMP
production was further improved by combining the above-mentioned pH-control system and fed-batch process with glucose at a
constant feeding rate of 1.0 g L−1 h−1. Under optimum conditions, the final cAMP production was 10.87 g L, which is 110.0, 46.7, and 27.7% higher than that of the
pH-uncontrolled, pH-controlled, and pH-shift controlled methods, respectively. 相似文献