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21.
目前几乎所有有机化学品和塑料是从原油和天然气中生产的, 而生物技术的应用使得利用可再生资源进行大规模化工生产成为可能。以下主要综述了白色生物技术, 即利用细菌、酵母或酶将可发酵糖转化为特定的化学产品的技术。白色生物技术极大节省了不可再生能源的消耗, 减少了温室气体的排放。在有利条件下, 如果化工生产中相关技术有了发展并且可以成功以木质纤维素为原料, 那么到2050年不可再生能源的消耗将减少将近2/3 (67%)。欧洲(EU-25)地区的分析表明, 白色生物技术相关的用地在未来几年的欧洲不会受到制约, 尤其是有大量闲置资源的东欧。另外, 虽然原则上可以在白色生物技术中使用自然的细菌和酶, 但是很多专家认为, 利用经遗传改造生物体(GMO)可以达到高产量、高浓度、高效率, 这对实现经济活力是必要的。值得注意的是, 目前并不是所有的重组基因和其他物种间的相互作用所带来的后果都可预见, 因此化工生产释放的GMOs的安全失活和处理非常重要, 但是如果采取足够的预防措施, 在白色生物技术中应用GMOs的风险是可以控制的。我们认为, 生物生产过程的技术突破、下游生产过程的控制、化石燃料的高价格、可发酵糖的低价获得是生物质化学产业发展中的关键因素, 这4个因素及其他伴随策略是发展整体白色生物技术的要求。 相似文献
22.
The cellobiose catabolic system of Escherichia coli K12 is being used to
study the role of cryptic genes in evolution of new functions. Escherichia
coli does not use beta-glucoside sugars; however, mutations in several loci
can activate the cryptic bgl operon and permit growth on the beta-glucoside
sugars arbutin and salicin. Such Bgl+ mutants do not use cellobiose, which
is the most common beta-glucoside in nature. We have isolated a Cel+
(cellobiose-utilizing) mutant from a Bgl+ mutant of E. coli K12. The Cel+
mutant grows well on cellobiose, arbutin, and salicin. Genes for
utilization of these beta-glucosides are located at 37.8 min on the E. coli
map. The genes of the bgl operon are not involved in cellobiose
utilization. Introduction of a deletion covering bgl does not affect the
ability to utilize cellobiose, arbutin, or salicin, indicating that the new
Cel+ genes provide all three functions. Spontaneous cellobiose negative
mutants also become arbutin and salicin negative. Analysis of
beta-glucoside positive revertants of these mutants indicates that there
are separate loci for utilization of each of the beta-glucoside sugars. The
genes are closely linked and may be activated from a single locus. A fourth
gene at an unknown location increases the growth rate on cellobiose. The
cel genes constitute a second cryptic system for beta-glucoside utilization
in E. coli K12.
相似文献
23.
Fasciocutaneous vessels in the upper arm: application to the design of new fasciocutaneous flaps 总被引:2,自引:0,他引:2
The principles of the blood supply to the upper arm are described. Despite the large, fleshy nature of the biceps and the triceps, the blood supply to upper arm skin is not from the underlying muscles, but is by fasciocutaneous perforators emerging along the medial and lateral intermuscular septa. Fifty dissections of preserved cadavers have shown that on the lateral side the fasciocutaneous perforators consistently arise from the middle collateral artery. The available length of this vessel and its diameter have been measured and are reported. The design of a flap based on this vessel, in a manner analogous to the Chinese forearm flap on the radial artery, is described. 相似文献
24.
25.
—Acetyl-CoA: 1,4-diaminobutane N-acetyltransferase catalyses the first step of putrescine catabolism in mammalian brain. It may be important in putrescine degradation of other tissues as well. Its specific activity is higher in homogenates of immature than of mature rat brains. A steady decline of putrescine acetylase activity is observed from birth until approx adult levels are reached at day 30. Microsomes and purified nuclei from brains of 2-day-old rats show considerably higher putrescine acetylase activities than the corresponding subcellular organelles from adult brains. Increased putrescine acetylase activities were found in nitroso-ethylurea-induced gliomas, together with a dramatic increase of putrescine concentration. High tissue concentrations of putrescine are, however, not necessarily correlated with enhanced putrescine acetylase activities. In trout brains a linear increase of acetyl-CoA: 1,4-diaminobutane N-acetyltransferase activity was observed together with a decrease of putrescine concentration after adaptation of the animals to increased water temperature. 相似文献
26.
Disturbance legacies and climate jointly drive tree growth and mortality in an intensively studied boreal forest 总被引:1,自引:0,他引:1
Ben Bond‐Lamberty Adrian V. Rocha Katherine Calvin Bruce Holmes Chuankuan Wang Michael L. Goulden 《Global Change Biology》2014,20(1):216-227
Most North American forests are at some stage of post‐disturbance regrowth, subject to a changing climate, and exhibit growth and mortality patterns that may not be closely coupled to annual environmental conditions. Distinguishing the possibly interacting effects of these processes is necessary to put short‐term studies in a longer term context, and particularly important for the carbon‐dense, fire‐prone boreal forest. The goals of this study were to combine dendrochronological sampling, inventory records, and machine‐learning algorithms to understand how tree growth and death have changed at one highly studied site (Northern Old Black Spruce, NOBS) in the central Canadian boreal forest. Over the 1999–2012 inventory period, mean tree diameter increased even as stand density and basal area declined significantly. Tree mortality averaged 1.4 ± 0.6% yr?1, with most mortality occurring in medium‐sized trees; new recruitment was minimal. There have been at least two, and probably three, significant influxes of new trees since stand initiation, but none in recent decades. A combined tree ring chronology constructed from sampling in 2001, 2004, and 2012 showed several periods of extreme growth depression, with increased mortality lagging depressed growth by ~5 years. Higher minimum and maximum air temperatures exerted a negative influence on tree growth, while precipitation and climate moisture index had a positive effect; both current‐ and previous‐year data exerted significant effects. Models based on these variables explained 23–44% of the ring‐width variability. We suggest that past climate extremes led to significant mortality still visible in the current forest structure, with decadal dynamics superimposed on slower patterns of fire and succession. These results have significant implications for our understanding of previous work at NOBS, the carbon sequestration capability of old‐growth stands in a disturbance‐prone landscape, and the sustainable management of regional forests in a changing climate. 相似文献
27.
Thomas Ryckmans Laurent Balan?on Olivier Berton Christophe Genicot Yves Lamberty Benedicte Lallemand Patrick Pasau Nathalie Pirlot Luc Quéré Patrice Talaga 《Bioorganic & medicinal chemistry letters》2002,12(2):261-264
Compounds combining NK(1) antagonism and serotonin reuptake inhibition are described, and potentially represent a new generation of antidepressants. Compound 24 displays good affinities for both the NK(1) receptor and the serotonin reuptake site (32 and 25 nM, respectively). 相似文献
28.
Steven E Reid Emily J Kay Lisa J Neilson Anne‐Theres Henze Jens Serneels Ewan J McGhee Sandeep Dhayade Colin Nixon John BG Mackey Alice Santi Karthic Swaminathan Dimitris Athineos Vasileios Papalazarou Francesca Patella Álvaro Román‐Fernández Yasmin ElMaghloob Juan Ramon Hernandez‐Fernaud Ralf H Adams Shehab Ismail David M Bryant Manuel Salmeron‐Sanchez Laura M Machesky Leo M Carlin Karen Blyth Massimiliano Mazzone Sara Zanivan 《The EMBO journal》2017,36(16):2373-2389
Tumor progression alters the composition and physical properties of the extracellular matrix. Particularly, increased matrix stiffness has profound effects on tumor growth and metastasis. While endothelial cells are key players in cancer progression, the influence of tumor stiffness on the endothelium and the impact on metastasis is unknown. Through quantitative mass spectrometry, we find that the matricellular protein CCN1/CYR61 is highly regulated by stiffness in endothelial cells. We show that stiffness‐induced CCN1 activates β‐catenin nuclear translocation and signaling and that this contributes to upregulate N‐cadherin levels on the surface of the endothelium, in vitro. This facilitates N‐cadherin‐dependent cancer cell–endothelium interaction. Using intravital imaging, we show that knockout of Ccn1 in endothelial cells inhibits melanoma cancer cell binding to the blood vessels, a critical step in cancer cell transit through the vasculature to metastasize. Targeting stiffness‐induced changes in the vasculature, such as CCN1, is therefore a potential yet unappreciated mechanism to impair metastasis. 相似文献
29.
Eicosapentaenoic and docosahexaenoic acids production by and okara-utilizing potential of thraustochytrids 总被引:3,自引:0,他引:3
K W Fan F Chen E BG Jones L LP Vrijmoed 《Journal of industrial microbiology & biotechnology》2001,27(4):199-202
Nine thraustochytrid strains isolated from subtropical mangroves were screened for their eicosapentaenoic acid (EPA) and docosahexaenoic
acid (DHA) production potential in a glucose yeast extract medium. Their ability to utilize okara (soymilk residue) for growth
and EPA and DHA production was also evaluated. EPA yield was low in most strains, while DHA level was high on glucose yeast
extract medium, producing 28.1–41.1% of total fatty acids, for all strains, with the exception of Ulkenia sp. KF13. The DHA yield of Schizochytrium mangrovei strains ranged from 747.7 to 2778.9 mg/l after 52 h of fermentation at 25°C. All strains utilized okara as a substrate for
growth, but DHA yield was lower when compared with fermentation in a glucose yeast extract medium. Journal of Industrial Microbiology & Biotechnology (2001) 27, 199–202.
Received 11 December 2000/ Accepted in revised form 29 June 2001 相似文献
30.