木薯和玉米原料丁醇发酵中丁醇丙酮质量比的图论理论计算及其验证

在丁醇发酵产溶剂阶段,乙酸和丁酸的生成途径、消耗途径同时存在,各自形成一个闭环路径。本研究利用图论对丁醇发酵中丁醇丙酮质量比进行了理论计算,并对以木薯和玉米为原料的丁醇发酵进行了模拟计算,结果表明:丁酸闭环路径(L2环)的代谢强度是影响丁醇丙酮质量比的主要因素,并且L2环的代谢强度越弱,丁醇丙酮质量比越高;与玉米原料丁醇发酵相比,木薯原料发酵的m(丁醇)/m(丙酮)提高了16.7%。实验结果证实了以上计算结果:在传统发酵、油醇萃取发酵和生物柴油萃取发酵中,以木薯(适时添加酵母浸粉)为原料的发酵批次与以玉米为原料的发酵批次相比,由于其丁酸闭环路径代谢强度较弱,相应发酵方式下丁醇丙酮质量比分别提高了12.9%、61.4%和6.7%,而且两种原料相应发酵方式的丁醇总产量和生产效率基本持平。另外,高丁醇丙酮质量比的木薯发酵所得改良型生物柴油中丁醇浓度与玉米发酵的相比提高了16%,性能得到进一步提高。     

添加有机酸对Clostridium acetobutylicum合成丙酮和丁醇的影响

为提高丙酮-丁醇梭菌厌氧发酵生产丙酮和丁醇的能力,在发酵过程中添加有机酸（乙酸和丁酸）,考察其对菌体生长、溶剂合成影响。实验表明：当添加1.5 g/L乙酸时能够促进菌体的生长,促进丙酮的合成,在600 nm处的最大OD值比参照值高出18.4%,丙酮的最终质量分数提高了21.05%,但不能促进丁醇的合成;当添加1.0g/L丁酸时能够促进菌体生长,促进丁醇的合成,在600 nm处的最大OD比参照值高22.29%,丁醇的最终质量分数比对照组提高了24.32%,但不能促进丙酮的合成。     

Pervaporative butanol fermentation by Clostridium acetobutylicum B18

Extractive acetone-butanol-ethanol (ABE) fermentation was carried out successfully using pervaporation and a low-acid-producing Clostridium acetobutylicum B18. A pervaporation module with 0.17 m(2) of surface area was made of silicone membrane of 240 mum thickness. Pervaporation experiments using make-up solutions showed that butanol and acetone fluxes increased linearly with their concentrations in the aqueous phase. Fickian diffusion coefficients were constants for fixed air flow rates, and increased at higher sweep air flow rates. During batch and fed-batch fermentations, pervaporation at an air flow rate of 8 L/min removed butanol and acetone efficiently. Butanol concentration was maintained below 4.5 g/L even though Clostridium acetobutylicum B18 produced butanol steadily. Pervaporation could not remove organic acids efficiently, but organic acids did not accumulate because strain B18 produced little organic acid and recycled added organic acids efficiently. With pervaporation, glucose consumption rate increased compared to without pervaporation, and up to 160 g/L of glucose was consumed during 80 h. Cell growth was not inhibited by possible salt accumulation or oxygen diffusion through the silicone tubing. The culture volume was maintained relatively constant during fed-batch operation because of an offsetting effect of water and product removal by pervaporation and addition of nutrient supplements. (c) 1994 John Wiley & Sons, Inc.     

Columnar cacti as sources of energy and protein for frugivorous bats in a semi‐arid ecosystem

Columnar cacti constitute the dominant elements in the vegetation structure of arid and semi‐arid New World ecosystems representing a plethora of food resources for vertebrate consumers. Previous stable isotope analysis in Central Mexico showed that columnar cacti are of low importance to build tissue for frugivorous bats. We used carbon stable isotope analysis of whole blood and breath samples collected from four species of frugivorous bats (Sturnira parvidens, Sturnira ludovici, Artibeus jamaicensis, and Artibeus intermedius) to reconstruct the importance of cactus plants in their diet. Breath samples were collected within 10 min (B₁₀) of bat capture and ~12 h after capture (B₇₂₀), representing the oxidation of recently ingested food and of body reserves, respectively. We expected that bats relied primarily on non‐cactus food to construct tissues and fuel oxidative metabolism. Non‐cactus food strongly predominated for tissue building, whereas oxidative metabolism was supported by a moderate preponderance of non‐cactus food for B₁₀ samples, and a moderate preponderance of cactus food or an equal contribution of both sources for B₇₂₀ samples. Artibeus and Surnira species appear to cover a narrow part of the diet with cactus food, confirming that the incorporation of nutrients derived from these plants is not generalized among vertebrate consumers.     

烟管菌漆酶的分离纯化及部分酶学性质研究

烟管菌Bjerkandera adustaWZFF.W-Y11漆酶粗酶液经过丙酮分级沉淀、DEAE-Cellulose离子交换层析、Sephadex G-100凝胶过滤,得到了三种电泳纯的漆酶同工酶,总酶活回收率达到65.5%,其中LacA平均纯化了29.2倍,LacB纯化了5.1倍,LacC纯化了18.5倍;三种同工酶的分子量分别为LacA:68.7kDa、LacB:80.2kDa、LacC:77.2kDa。LacA、LacC氧化愈创木酚的Km大于氧化ABTS的Km,最适作用温度在45-70℃,最适反应pH3.0-5.5,65℃时LacC比LacA稳定,LacC在pH3.5-6.0稳定,LacA在pH5.0-9.0稳定,Al3+对LacA、LacC的酶活有促进作用,Cl-、Fe3+、Hg2+抑制LacA、LacC的酶活,Cu2+抑制LacC的酶活,而对LacA的活性没有明显影响。     

The flavoproteome of the yeast Saccharomyces cerevisiae

Genome analysis of the yeast Saccharomyces cerevisiae identified 68 genes encoding flavin-dependent proteins (1.1% of protein encoding genes) to which 47 distinct biochemical functions were assigned. The majority of flavoproteins operate in mitochondria where they participate in redox processes revolving around the transfer of electrons to the electron transport chain. In addition, we found that flavoenzymes play a central role in various aspects of iron metabolism, such as iron uptake, the biogenesis of iron–sulfur clusters and insertion of the heme cofactor into apocytochromes. Another important group of flavoenzymes is directly (Dus1-4p and Mto1p) or indirectly (Tyw1p) involved in reactions leading to tRNA-modifications. Despite the wealth of genetic information available for S. cerevisiae, we were surprised that many flavoproteins are poorly characterized biochemically. For example, the role of the yeast flavodoxins Pst2p, Rfs1p and Ycp4p with regard to their electron donor and acceptor is presently unknown. Similarly, the function of the heterodimeric Aim45p/Cir1p, which is homologous to the electron-transferring flavoproteins of higher eukaryotes, in electron transfer processes occurring in the mitochondrial matrix remains to be elucidated. This lack of information extends to the five membrane proteins involved in riboflavin or FAD transport as well as FMN and FAD homeostasis within the yeast cell. Nevertheless, several yeast flavoproteins, were identified as convenient model systems both in terms of their mechanism of action as well as structurally to improve our understanding of diseases caused by dysfunctional human flavoprotein orthologs.     

Real-time measurement of particulate matter deposition in the lung

Abstract

Air pollution and cigarette smoke are recognized health risks. A method was developed for the measurement of the deposition fraction (DF) of polydisperse particulate matter (PM) in human airways. Ten normal volunteers [three females, age range 18–67 years, mean age (SD) 43.9 (14)] made single breath exhalations after inhalation to total lung capacity. The exhaled breath was diverted to a multichannel laser diffraction chamber where the particulate profiler measured 0.3–1.0-µm particles. DF was inversely related to expiration flow-rate, 0.69 (0.02) at 4 l min^?1 and 0.5 (0.01) at 13 l min^?1, respectively (p<0.05), and was influenced by the inhalation flow-rate [0.70 (0.02) at 3 l min^?1 and 0.59 (0.02) at 13 l min^?1, respectively (p<0.05)], while no differences were found between nasal and oral inhalation (0.68 (0.05) versus 0.67 (0.06), p>0.05). Higher breath holding times were associated with elevated DF [0.74 (0.02) at 20 s, and 0.62 (0.05) without breath holding (p<0.01)]. When the expiratory flow was controlled and the breath hold time standardized, DF was reproducible (CV?=?4.85%). PM can be measured in the exhaled breath and its DF can be quantified using a portable device. These methods may be useful in studies investigating the health effects of air pollution and tobacco smoke.     

定点突变提高虎杖聚酮合酶的苯亚甲基丙酮合酶活性北大核心CSCD

虎杖(Polygonum cuspidatum)聚酮合酶(polyketide synthase 1,PcPKS1)同时具有查尔酮合酶(chalcone synthase,CHS)及苯亚甲基丙酮合酶(benzylidene acetone synthase,BAS)催化活性,能够催化生成聚酮类化合物柚皮素查尔酮和苯亚甲基丙酮,进而催化合成黄酮类或覆盆子酮等具有多种生物学活性的化合物。本研究通过分析虎杖PcPKS1与掌叶大黄(Rheum palmatum)BAS、拟南芥(Arabidopsis thaliana)CHS等家族成员的序列以及酶催化位点的构象,确定可能影响酶功能的3个氨基酸位点:Thr133、Ser134、Ser339。采用定点突变对PcPKS1进行分子修饰,成功获得2个突变体并进行相关体外酶促反应,高效液相色谱(high performance liquid chromatography,HPLC)产物分析结果表明,在pH 7.0和pH 9.0的体外酶促条件下,突变体T133LS134A和S339V维持BAS和CHS双功能活性,且BAS活性显著高于原PcPKS1。本研究为利用PcPKS1进行基因工程调节黄酮类和覆盆子酮化合物的生物合成提供理论依据。     

Exhaled 8-isoprostane in childhood asthma

Background

In the backdrop of conflicting reports (some studies reported adverse outcomes of biomass fuel use whereas few studies reported absence of any association between adverse health effect and fuel use, may be due to presence of large number of confounding variables) on the respiratory health effects of biomass fuel use, this cross sectional survey was undertaken to understand the role of fuel use on pulmonary function.

Method

This study was conducted in a village of western India involving 369 randomly selected adult subjects (165 male and 204 female). All the subjects were interviewed and were subjected to pulmonary function test. Analysis of covariance was performed to compare the levels of different pulmonary function test parameters in relation to different fuel use taking care of the role of possible confounding factors.

Results

This study showed that biomass fuel use (especially wood) is an important factor for deterioration of pulmonary function (particularly in female). FEV₁ (p < .05), FEV₁ % (p < .01), PEFR (p < .05) and FEF_25–75 (p < .01) values were significantly lower in biomass fuel using females than nonusers. Comparison of only biomass fuel use vs. only LPG (Liquefied Petroleum Gas) use and only wood vs. only LPG use has showed that LPG is a safer fuel so far as deterioration of pulmonary function is concerned. This study observes some deterioration of pulmonary function in the male subjects also, who came from biomass fuel using families.

Conclusion

This study concluded that traditional biomass fuels like wood have adverse effects on pulmonary function.     

Controllable regioselective enzymatic synthesis of polymerizable 5′-O-vinyl- and 3′-O-vinyl-nucleoside analogues in acetone

An efficient synthesis of polymerizable 3'- and 5'-O-acyl-nucleoside derivatives has been developed from inosine and 2'-deoxyuridine by enzyme-catalyzed regioselective acylation with divinyl dicarboxylates. In acetone, Lipozyme (immobilized lipase from Mucor miehei) gave 5'-O-acyl-nucleoside products, and PPL (lipase from porcine pancreas) provided 3'-O-acyl-nucleoside products.