Breeding of high malate‐producing diploid sake yeast with a homozygous mutation in the VID24 gene

Malate is an important taste component of sake (a Japanese alcoholic beverage) that is produced by the yeast Saccharomyces cerevisiae during alcoholic fermentation. A variety of methods for generating high malate‐producing yeast strains have been developed to date. We recently reported that a high malate‐producing strain was isolated as a mutant sensitive to dimethyl succinate (DMS), and that a mutation in the vacuolar import and degradation protein (VID) 24 gene was responsible for high malate productivity and DMS sensitivity. In this work, the relationships between heterozygous and homozygous mutants of VID24 and malate productivity in diploid sake yeast were examined and a method was developed for breeding a higher malate‐producing strain. First a diploid yeast was generated with a homozygous VID24 mutation by genetic engineering. The homozygous integrants produced more malate during sake brewing and grew more slowly in DMS medium than wild‐type and heterozygous integrants. Thus, the genotype of the VID24 mutation influenced the level of malate production and sensitivity to DMS in diploid yeast. Then a homozygous mutant from a heterozygous mutant was obtained without genetic engineering by ultraviolet irradiation and culturing in DMS with nystatin enrichment. The non‐genetically modified sake yeast with a homozygous VID24 mutation exhibited a higher level of malate productivity than the parent heterozygous mutant strain. These findings provide a basis for controlling malate production in yeast, and thereby regulating malate levels in sake. Copyright © 2016 The Institute of Brewing & Distilling     

Acrylamide elution from roasted barley grains into mugicha and its formation during roasting

This paper investigated acrylamide elution from roasted barley grain into mugicha and its formation during roasting of the grain. Mugicha is an infusion of roasted barley grains. Highly water-soluble acrylamide was easily extracted to mugicha from milled roasted barley grains in teabags. On the other hand, the acrylamide concentration in mugicha prepared from loose grain increased with longer simmering and steeping times. During roasting in a drum roaster, the acrylamide concentration of the grain increased as the surface temperature rose, reaching a maximum at 180–240°C. Above this temperature, the acrylamide concentration decreased with continued roasting, exhibiting an inverted ‘U’-shaped curve. For most of the samples, the acrylamide concentration showed good correlation with the value of the colour space parameter L*. The dark-coloured roasted barley grains with lower L* values contained lower amounts of acrylamide as a result of deep roasting. The level of asparagine in barley grains was found to be a significant factor related to acrylamide formation in roasted barley products. The data are an important contribution to the mitigation of acrylamide intake from mugicha.     

Analysis of Cs-adsorption behavior using a column filled with microcapsule beads of potassium copper hexacyanoferrate

Ash-washing technology is a crucially important technology for removing radioactive Cs from contaminated ash. For that technology, Cs⁺ removal from the ash-washing solution by the adsorbent is necessary. This study was conducted to establish rapid preparation of appropriate adsorption columns for Cs⁺ uptake. A one-site model was not used for analysis because the model cannot accommodate sites with different adsorption speed. Results demonstrated that the adsorption behavior of the column filled with the granules of potassium copper hexacyanoferrate was well reproduced by a two-site adsorption model with parameters chosen through analysis of batch adsorption test results.     

基于常时微动观测的钢筋混凝土建筑物振动特性及其地域差异

文章以呼和浩特市区钢筋混凝土建筑物为研究对象, 实施常时微动观测,分析了建筑物的振动特性,以及通过把呼和浩特市与其他地区的观测数据进行比较研究,初步探索了钢筋混凝土建筑物振动特性的地域差异,并得出如下结论: ⑴建筑物的第一次共振周期与楼层数或高度存在正相关关系,而楼层相同时则与建筑年代呈反相关关系,且大多数建筑物具有短轴方向的共振周期与长轴方向相同或较之偏大等特征。⑵大多数建筑物与地基间有着一定的相互作用。⑶同样建筑比较而言,福冈市的建筑物共振周期最小,乌兰巴托市最大,呼和浩特市和台中市的建筑物共振周期因长、短轴方向差异而大小不同。     

Intracellular DNA damage induced by non-thermal, intense narrowband electric fields

Intracellular DNA damages caused by intense burst sinusoidal electric fields (IBSEFs) were investigated by means of an alkaline comet assay method. Non-thermal, 200 ?s-long IBSEF with various frequency values (300 kHz-100MHz) and strengths (up to 200 kV/m) was applied to Chinese hamster ovary (CHO) cells in a suspending medium between 1 mm gap parallel electrodes. The comet assay suggests that 100 kV/m IBSEF with frequencies exceeding 1 MHz or 100 MHz IBSEFs with field strengths exceeding 3 kV/m induces significant DNA damage. According to the numerical calculation of the electric field over a simplified cell model under an alternating electric field, the intracellular field strength increases with increasing alternating frequency. The minimum level of the field strength that induces the DNA damage is in the range of 10-30 kV/m. This intracellular strong field might trigger biological processes leading to the DNA damage.     

Observation of small fatigue crack growth behavior in the extremely low growth rate region of low carbon steel in a hydrogen gas environment

To investigate the effects of hydrogen on crack propagation in the extremely low growth rate range, fully reversed bending fatigue tests were performed on low carbon steel (JIS S10C) in hydrogen and in nitrogen gas environments at a low pressure. A crack showed almost the same non-propagation behavior in nitrogen as that in air. However, a crack in hydrogen continued to propagate even near $10^{7}$ cycles in the same testing strain range as that in nitrogen. In hydrogen gas, a crack grew intermittently by coalescing with a new micro-crack generated by slip behavior. This implies that hydrogen could inhibit the action of any factor affecting non-propagation.