Accumulation of 2-Keto-L-Gulonate at 33℃ by a Thermotolerant Gluconobacter Oxydans Mutant Obtained by Ion Beam Implantation

To obtain thermotolerant mutants of G. oxydans, which can enhance the transformation rate of L-sorbose to 2-Keto-L-gulonate （2-KLG） at 33℃ in a two-step process of vitamin C manufacture, ion beam was used as a mutation source. Gluconobacter oxydans GO and Bacillus megaterium B0 were used in this study. The original strain Gluconobacter oxydans GO was mutated by the heavy ion implantation facility at the Institute of Plasma Physics, Chinese Academy of Sciences. Several mutants including Gluconobacter oxydans GI13 were isolated and cocultured with Bacillus megaterium B0 at 33℃ in shaking flasks. The average transformation rate of the new mixed strain GI13-B0 in per gram-molecule reached 94.4% after seven passages in shaking flasks, which was increased by 7% when compared with the original mixed strain G0-B0 （Gluconobacter oxydans GO and Bacillus megaterium B0）. Moreover, the transformation rate of I13B0 was stable at 94% at temperatures ranging from 25℃ to 33℃, which would be of much value in reducing energy consumption in the manufacture of L-ascorbic acid, especially in the season of summer. To clarify some mechanism of the mutation, the specific activities of L-sorbose dehydrogenase in both GO and GI13 were estimated.     

A Preliminary Study of the Application of a Model Animal-Caenorhabidity elegans＇ Exposure to a Low-Energy Ion Irradiation System

Because of the lack of suitable animal models adapted to high vacuum stress in the low-energy ion implantation system, the bio-effects ion irradiation with an energy less than 50 keV on multi-cellular animal individuals have never been investigated so far. The nematode Caenorhabditis elegans has proved to be an excellent animal model used for the study of a broad spectrum of biological issues. The purpose of this work was to investigate the viability of this animal under ion irradiation. We studied the protection effects of glycerol and trehalose on the enhancement of nematodes＇ ability to bear the vacuum stress. The results showed that the survival of the nematodes was enhanced remarkably under long and slow desiccation, even without glycerol and trehalose. 159 glycerol showed a better anti-vacuum stress effect on the nematodes than trehalose did under short-time desiccation. Low-temperature pre-treatment or post-treatment of the samples had no obvious effect on the survival scored after argon ion irradiation. Moreover, little effect was induced by 15% glycerol- and vacuum-exposure on germ cell apoptosis, compared to the untreated control sample. It issuggested that such treatment would provide relatively low background for genotoxic evaluations with ion irradiation.     

用H_2O_2,O_3和ClO_2漂白针叶木硫酸盐浆

用Ｈ２Ｏ２，Ｏ３和ＣｌＯ２漂白针叶木硫酸盐浆ＢｌｅａｃｈｉｎｇｏｆｓｏｆｔｗｏｏｄｋｒａｆｔｐｕｌｐｓｗｉｔｈＨ２Ｏ２，Ｏ３，ａｎｄＣｌＯ２一、前言近年来，全无氯漂白（ＴＣＦ）技术发展非常迅速。１９９０年首次报道了在工业上应用ＴＣＦ漂白技术，当时，用...     

水泥路面拉毛机液压系统

水泥路面施工工艺比较复杂，有摊铺、振捣、抹光、拉毛四道工序。而拉毛工序必须在水泥路面初凝之后进行。由于人工拉毛质量难以保证，而购买进口拉毛机价格昂贵。所以，国内已有许多单位在研究与开发。笔者通过广泛的调研，对水泥路面拉毛机进行了初步的设计。该机为两履带行走，采用四点找平液压缸构成的浮动机架调子系统和拉毛滚安装在拉毛滚架上，而拉毛滚架相对于主机架可垂直升降的机构。拉毛滚拉毛与履带行走方向相垂直，即纵向行走，横向拉毛。本文仅对该机液压系统加以分析与介绍，液压系统见图1。l行走液压系统由于水泥路面拉毛机…     

轴向柱塞泵泄漏的检测与修理

轴向柱塞泵压力高、排量大、易于实现变量,但其使用条件要求较高,对液压油的黏度、清洁度、泵转速、自吸条件的要求都较高。当某些条件不能满足要求时,将会导致其工作能力迅速下降甚至损坏,其中最常见就是造成泄漏迅速增大,有时会完全丧失工作能力。本文以XB型轴向柱塞泵为例,对轴向柱塞泵的泄漏、原位简易检测和修复进行探讨,以期对使用与维修有所帮助。1轴向柱塞泵的泄漏图1是XB型柱塞泵的结构简图,能够形成泄漏的部位在图中以带括号的数字标出。需要说明的是,这些部位在工作时都有正常泄漏,问题是使用过程中由于某些使用条件的不满足,…     

胡萝卜发根培养甘薯茎线虫体系研究

利用发根农杆菌转化的胡萝卜发根建立了甘薯茎线虫的单寄主培养体系,观察了甘薯茎线虫的行为及生活史。结果表明：在胡萝卜发根上培养甘薯茎线虫,便于研究其行为,可以清楚地观察到线虫在根毛处自由取食及侵入发根内部活动情况;雌虫可以正常产卵,线虫在20～25天内完成正常的生活史。基于观察到的上述结果,初步证实了所构建的胡萝卜发根培养甘薯茎线虫体系的可行性。     

西部严寒地区公共建筑遮阳技术研究

严寒地区供热周期普遍长达半年以上,冬季供热能耗远大于夏季供冷能耗。该地区采取遮阳措施后可以减少太阳辐射,降低夏季制冷能耗,但同时会导致冬季的供热能耗增加。本文探讨了西部严寒地区某公共建筑采用不同遮阳措施后的全年能耗。结果显示：内遮阳可有效降低建筑夏季能耗。采用高反低透的材料,全年能耗增加6%。若内遮阳考虑“人为干预”,可实现夏季节能率25%。