Correlated changes in skeletal muscle connective tissue and flesh texture during starvation and re‐feeding in brown trout (Salmo trutta) reared in seawater

Quantitative and qualitative changes to muscle and collagen were analysed following starvation and re‐feeding of brown trout (Salmo trutta) reared in seawater. Fish were submitted to starvation for 2 months followed by re‐feeding for 1 month and compared with a control group continuously fed. Classical effects of starvation on growth and morphometrics traits were observed with only a partial recovery of these parameters after 1 month of re‐feeding. Muscle composition of starved fish was significantly affected (lower dry matter content and higher post‐mortem pH) compared with control fish and was partially recovered in re‐fed fish compared with continuously fed fish. Muscle structure and composition were affected with thinner muscle fibre and higher connective tissue content for the starved fish but similar thickness of myosepta compared with the control group. No difference was observed after 1 month of re‐feeding. Characteristics of the connective tissue were significantly affected by starvation (more high weight molecular collagen form, higher thermal stability of skin collagen). These differences remained significant after the re‐feeding period. Starved fish showed also higher mechanical resistance of the raw flesh compared with the control group, but no difference in rheological measurements was observed after 1 month of re‐feeding. The changes in texture and their relationships with muscle composition, muscle structure and collagen characteristics are discussed. Copyright © 2004 Society of Chemical Industry     

THE ATTACHMENT OF BREWING YEAST TO GLASS

The secondary conditioning of cask and bottled beer with live yeast is normally facilitated by ensuring the sedimentation of the yeast to the base of the package prior to dispense. Here we examine the resistance of yeast sediment to disruption in bottled conditioned beer by investigating the attachment of brewing yeast to glass. An attachment assay is described which, when applied to brewing yeast, demonstrated that these yeasts are not naturally adhesive. However, yeast may be encouraged to form an attached mat by the physiological manipulation of starvation. The significance of this observation is discussed in relation to the effect of beer composition on yeast attachment.     

Nitrogen starvation induces expression of Lg‐FLO1 and flocculation in bottom‐fermenting yeast

When exponentially growing cells of bottom‐fermenting yeast were starved for nitrogen or were grown on proline (a non‐preferred nitrogen source), flocculation was induced. This flocculation was not induced by starvation for either carbon or amino acids. Expression of Lg‐FLO1, which is required for flocculation of bottom‐fermenting yeast, was also found to be induced by starvation for nitrogen. This suggests that the flocculation of bottom‐fermenting yeast is under the control of a nitrogen catabolite repression (NCR)‐like mechanism. Copyright © 2012 John Wiley & Sons, Ltd.     

Stresses on immobilized phanerochaete chrysosporium hyphae in submerged cultures for ligninase production

Effects of hydraulic shear stress and oxygen starvation stress on immobilized white-rot fungus Phanerochaete chrysosporium in submerged cultures for ligninase production were studied. The immobilized fungal hyphae formed an even mycelial mat on a rotating cylindrical stainless steel net showing little sensitivity to the shear stress. The average activity of ligninase over 24 h during a peak production period was 389 U/L at a tip velocity of 0.44 m/s and 369 U/L at a doubled tip velocity of 0.88 m/s. When the dissolved oxygen level dropped below 1 mg/L, the fungal cells responded to the oxygen starvation stress and released a considerable amount of protease. The proteolytic denaturation of ligninase was the major reason that a negligible ligninase activity was detected at a low aeration rate.     

原位氮饥饿发酵工艺中梯度补氮对谷氨酰胺合成酶的调控

The effects of uniform and gradient fed nitrogen on glutamine synthetase (GS), glutamate dehydrogenase(GDH) and glutamate synthase ((K)GAT)were investigated in glutamine production by fermentation of Corynebacterium glutamicum NS611 after 3 h of in-situ nitrogen starvation. It was shown that the strain in the later growth phase entered naturally into in-situ nitrogen starvation by controlling the initial concentration of urea and the biomass was slightly decreased. The pH value reached 6.5 again in the culture system, which confirmed the beginning of nitrogen starvation in the culture system. After 3 h nitrogen starvation the activity of GS was increased over two folds and the time of high activity of GS persisted three folds longer in the gradient fed nitrogen system than that in the normal fed batch. The higher activity of GDH was also maintained. The glutamine production increased by 72 % than the original technology of nitrogen starvation and the time of fermentation was shortened by above 12 h.     

Parametric study of kW-class solid oxide fuel cell stacks fueled by hydrogen and methane with fully multiphysical coupling model

Multiphysics models are important tools for the design and optimization of solid oxide fuel cells (SOFCs). The computational efficiency of a sophisticated multiphysics model is improved by a factor of 4 by symmetry utilization and grid optimization, allowing its routine use for the analysis and diagnosis of industrial-sized SOFC stacks. The predictive power of the model is tested by the experimental data. Parametric numerical studies, together with indepth theoretical analyses, on the performance characteristics of kW-class stacks fueled by H₂ and CH₄ are carried out with this accurate model. It is concluded: (1) CH₄ is advantageous for providing lower maximum temperature and temperature gradient, and higher energy efficiency. (2) H₂ is advantageous for generating more electricity and being more resistant to fuel starvation. (3) Insufficient air supply can cause high thermal gradient. (4) Fuel uniformity is critically dependent on the stack design and affects all aspects of stack performance.     

Thickness effects of anode catalyst layer on reversal tolerant performance in proton exchange membrane fuel cell

Real-world driving conditions will likely cause hydrogen starvation at the anode chambers of stacks to trigger voltage reversal events, posing a tremendous challenge to the durability of proton exchange membrane fuel cells (PEMFCs). The reversal-tolerant anode (RTA), a material-based solution, that inclusion of oxygen evolution reaction (OER) catalyst into the anode is usually employed to cope with the voltage reversal issue. In this work, we investigate the impact of anode catalyst layer thickness on the voltage reversal performance of the membrane-electrode assemblies (MEAs) with conventional anodes (Pt/C catalyst) and RTAs doped with IrO₂ catalyst, a representative OER catalyst. We find that regardless of how thick the anode catalyst layer is, the conventional MEAs exhibit almost similar voltage reversal behaviors and times, only about 1 min to reach the shutdown voltage (?2.5 V). As for the RTA MEAs, a surprising thickness effect that the thinner RTA with the same IrO₂ loading shows superior voltage reversal tolerance. Notably, an ultra-thin RTA (~2 μm) exhibits the reversal tolerance time of 310 min, which is five times higher reversal tolerance time than most of the reported RTAs. We conclude that this thickness effect mainly results from the ionomer distribution on the OER catalyst. Besides, we observe that the RTA with a higher ionomer content shows the better reversal tolerance performance. Our work highlights the importance of the OER Triple-Phase-Boundary (TPB) and the need for improved electrode designs for robust RTAs.     

乏油与表面划痕对纯滑动弹流接触的影响的实验研究

实验研究全膜和乏油条件下钢球表面划痕对弹流润滑的影响。使用光干涉技术观测轻载和重载时全膜和乏油条件下划痕在不同位置处接触区油膜的形状,使用MBI软件测量油膜中截面曲线。结果表明:与光滑表面结果相比,划痕在轻载条件下对油膜波动的影响更大;与全膜润滑结果相比,乏油降低了划痕对油膜分布产生的波动,并且改变了凹谷的弹性变形。     

Genome-Wide Identification and Characterization of Carboxypeptidase Genes in Silkworm (Bombyx mori)

The silkworm (Bombyx mori) is an economically-important insect that can secrete silk. Carboxypeptidases have been found in various metazoan species and play important roles in physiological and biochemical reactions. Here, we analyzed the silkworm genome database and characterized 48 carboxypeptidases, including 34 metal carboxypeptidases (BmMCP1–BmMCP34) and 14 serine carboxypeptidases (BmSCP1–BmSCP14), to better understand their diverse functions. Compared to other insects, our results indicated that carboxypeptidases from silkworm have more family members. These silkworm carboxypeptidases could be divided into four families: Peptidase_M2 carboxypeptidases, Peptidase_M14 carboxypeptidases, Peptidase_S10 carboxypeptidases and Peptidase_S28 carboxypeptidases. Microarray analysis showed that the carboxypeptidases had distinct expression patterns, whereas quantitative real-time PCR demonstrated that the expression level of 13 carboxypeptidases significantly decreased after starvation and restored after re-feeding. Overall, our study provides new insights into the functional and evolutionary features of silkworm carboxypeptidases.