Acetylation of loofa (Luffa cylindrica) sponge as immobilization carrier for bioprocesses involving cellulase

The feasibility of using loofa sponge for immobilization of cellulase-producing microorganisms was investigated by acetylating loofa sponge. Acetylation was achieved by autoclaving process of loofa sponge immersed in acetic anhydride at various temperatures for various times. The degree of acetylation, as inferred by the weight percentage gain (WPG), was enhanced by increasing both temperature and the duration of acetylation. The acetylation of a piece of loofa sponge in an autoclave at 120 degrees C for 20 min resulted in a WPG of about 8%, which was sufficient to protect the loofa sponge against cellulose degradation. The acetylated loofa sponge prepared under this condition was not decomposed by commercial cellulase and its structure was maintained for more than 720 h during repeated-batch treatments with commercial cellulase. A flocculating yeast (Saccharomyces cerevisiae IR-2) and a fungus (Trichoderma reesei QM9414) were successfully immobilized in the acetylated loofa sponge. In each case, the percentage of immobilized cells was as high as that obtained using nonacetylated loofa sponge. Acetylation had no adverse effects on cell growth and immobilization of T. reesei QM9414, as well as on cell growth and ethanol production by S. cerevisiae IR-2. T. reesei QM9414 immobilized on an acetylated loofa sponge was successfully used for repeated-batch cellulase production from commercial cellulose powder. Although the acetylated loofa sponge showed a slight weight loss, it was not disintegrated by activated sludge. The results obtained in this study showed that acetylated loofa sponge is suitable as an immobilization carrier for bioprocesses involving cellulase.     

Fundamentals of cell proliferation: control of the cell cycle

Cell proliferation in higher eukaryotes is controlled by the extracellular environment and the state of differentiation. Many cells exist in a nondividing growth state termed quiescence. Some quiescent cells cannot proliferate and are said to be terminally differentiated. Others can be stimulated to divide in response to environmental signals or when cell replacement is needed. Finally, some cells undergo continual proliferation and differentiation. Growth regulatory factors generally act at specific stages of the cell cycle, most commonly during the first gap phase of the cell cycle. Once cells initiate DNA synthesis, they are generally committed to complete DNA replication. After DNA synthesis, additional signals determine whether cells in the last gap phase proceed through mitosis. In recent years, genes that appear to be critical for progression through the first two gap phases have been identified. Many are proto-oncogenes and therefore can neoplastically transform certain cells when mutated or inappropriately expressed. Growth factors that stimulate proliferation induce the expression of several proto-oncogenes; growth inhibitory factors often suppress proto-oncogene expression. As cells differentiate, the response to extracellular factors changes. In many cases, this may be due to intracellular controls that alter the response of certain proto-oncogenes to external signals.     

Refinement of inverter model considering dead‐time for performance improvement in predictive instantaneous current control

Model predictive instantaneous‐current control (MPIC), which was proposed in our earlier works, enables us to achieve better instantaneous current control using mathematical models of an inverter and permanent magnet synchronous motors (PMSMs). However, dead‐time to avoid short breakdown in the inverter is not usually considered in a general inverter model. Such an unmodeled part in the inverter model prevents accurate prediction of current evolution in motor systems based on the model predictive control. Therefore, in this paper, we analyze current response resulting from the dead‐time in the MPIC, and propose a refined inverter model considering the dead‐time so that control performance is improved. The effectiveness of the proposed method is verified through simulation and experiments. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Levels of phthalates and adipates in processed foods and migration of di-isononyl adipate from polyvinyl chloride film into foods

The levels of dibutyl phthalate (DBP), butylbenzyl phthalate (BBP), di-(2-ethylhexyl) phthalate (DEPHP), di-isononyl phthalate (DINP), di-(2-ethylhexyl) adipate (DEHA) and di-isononyl adipate (DINA) were determined in 50 processed foods (ham and sausage, fried dumpling and shao-mai, fish paste products, croquette and fried fish, bread, noodle, pickles, etc.). DBP, BBP, DEHP, DINP, DEHA, and DINA were contained at nd approximately 47.7, nd approximately 16.6, nd approximately 749, nd approximately 358, nd approximately 57.2 and nd approximately 20,200 ppb, respectively. High-level contamination of DINA was found in fish paste products, croquette and shao-mai, presumably because of migration from plasticized wrapping film using for food packaging. We studied the relationship between DINA migration from wrapped PVC film into fried croquette and its standing time after frying. When the croquette was wrapped immediately after frying, the migration from wrapping film into the croquette was highest (36,400 ng/g). On wrapping after standing for 5 min and 30 min, the migration level was reduced to 1/3.5 and 1/14 of the highest level, respectively.     

A rapid-detection method for radioactive cesium in the air

We propose a method of rapidly detecting radioactive cesium floating in the air for the purpose of alerting people active in the ‘difficult-to-return zone’ of Fukushima to changes in airborne radioactivity. With this purpose in mind, we set requirement specifications and created a new system concept. The targeted detection limit was 30 Bq/m³ and the mandatory level of measurement time was 48 min with a target level of 12 min, and these periods are 10 times faster than those of conventional air monitors. The system consists of a conventional gamma-spectrometer with a novel shaped shield. The targeted peak region of the measured energy spectrum is analyzed. After the basic design and confirmation of feasibility, we perform some experiments in the normal environment of Yokohama city and the difficult-to-return zone of Fukushima. Using the results, we conducted the design improvement and performance evaluation. As a result, the system performance is found to satisfy requirements. We thus conclude that this system is a promising candidate for rapid detection of airborne radioactivity in the difficult-to-return zone of Fukushima.     

In situ time-resolved X-ray diffraction of tobermorite formation in autoclaved aerated concrete: Influence of silica source reactivity and Al addition

The hydrothermal formation of tobermorite during the processing of autoclaved aerated concrete was investigated by in situ X-ray diffraction (XRD) analysis. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used.To investigate the effects of the silica source, reactive quartz from chert and less-reactive quartz from quartz sand were used as starting materials. The effect of Al addition on tobermorite formation was also studied. In all cases, C-S-H, hydroxylellestadite and katoite were clearly observed as intermediates.Acceleration of tobermorite formation by Al addition was clearly observed. However, Al addition did not affect the dissolution rate of quartz. Two pathways, via C-S-H and katoite, were also observed in the Al-containing system. These results suggest that the structure of initially formed C-S-H is important for the subsequent tobermorite formation reactions.     

Control of carbon incorporation in AlAs grown by atomic layer epitaxy using variously orientated substrates

We demonstrate a method for successfully controlling carbon incorporation in AlAs layers grown by atomic layer epitaxy (ALE) using various GaAs substrates with different orientations. The number of alkyl radicals attached to an Al atom at the surface, which is a main factor in carbon incorporation, can be intentionally controlled by changing substrate orientation. We found that the carbon incorporation in ALE-AlAs using the (3 1 1)B surface is 2 x 10¹⁷,cm^-3, which is the lowest value ever reported for ALE-AlAs that satisfies one-monolayer self-limiting growth conditions.     

Kinetics of solid acid catalyzed 1-octene reactions with TiO2 in sub- and supercritical water

Acid catalyzed reactions of 1-octene on TiO₂ in sub- and supercritical water were investigated (T = 250-450 °C, P = 11-33 MPa). The main products were 2-octene and 2-octanol. Additionally, other liner C₈ alkenes and liner secondary C₈ alcohols were produced as by-products. Through kinetic analysis, acid catalyzed reactions can divide into the reaction catalyzed by Lewis acidic sites on TiO₂ and the reaction catalyzed by protons produced by the dissociation of water molecules. Each type of the reaction is affected by water density or ionic product of water, respectively, therefore, reaction mechanism changes with temperature and pressure. From the contribution of each reaction type, the temperature dependence of cis/trans ratio of produced 2-octene could also be explained.     

Correction and evaluation of the effect due to parasitic motion on primary accelerometer calibration

Primary accelerometer calibration is carried out under the assumption that a vibration exciter gives a rectilinear motion to an accelerometer to be calibrated. However practical vibration given by the vibration exciter includes parasitic motion such as transverse, rocking, and bending motion. Such parasitic motion would give two serious effects on primary calibration results, transverse motion effect and vibration distribution effect. Transverse motion effect is caused by an inner product of the vectors of both transverse motion and transverse sensitivity. On the other hand, the vibration distribution effect is caused by relative motion between a sensing point of accelerometer and a spot sensed by the interferometer. As these effects have close interaction between parasitic motion and measuring instruments, it would be very difficult to evaluate them by measuring independently each component.