The regulation of Mn2+ and Cu2+ uptake in cells of the yeast Candida utilis grown in continuous culture

Abstract Transport of Mn²⁺ was repressed in Candida utilis cells grown in continuous culture in high-Mn²⁺ (100 μM Mn²⁺) medium as compared to cells grown in basic (0.45 μM Mn²⁺) and low-Mn²⁺ (< 0.05 μM Mn²⁺) media. In contrast, no repression of Cu²⁺ uptake occurred in high-Cu²⁺-grown (25 μM Cu²⁺) cells as compared to cells grown in basic medium (0.54 μM Cu²⁺). Cu²⁺-limited cells did not hyperaccumulate Cu²⁺ and there was not significant difference in initial uptake rates for all 3 Cu²⁺ conditions. Mn²⁺ uptake appears to be regulated by a mechanism sensitive to the external Mn²⁺ concentration, whereas Cu²⁺ transport is not governed in this way by the external Cu²⁺.     

高效液相色谱法测定猫豆中左旋多巴的含量

本文用高效液相色谱法测定了猫豆中主旋多巴［Ｌｅｖｏｄｏｐａ］的含量。考察了加样回收率为９８．７０％,变异系数为１．９９％。     

菜心溶菌酶的提纯及酶学性质

菜心（ＢｒａｓｓｉｃａｃａｍｐｅｓｔｒｉｓＬ．ｓｓｐ．ｃｈｉｎｅｎｓｉｓｖａｒ．ｕｔｉｌｉｓ）叶子高速捣碎后,滤液经酸碱处理,硫酸铵分步沉淀,凝胶柱层析等步骤分离纯化溶菌酶,酶比活力达３４１４．６Ｕ／ｍｇ,纯化倍数为１９７．４。菜心溶菌酶在较宽的温度或ｐＨ值范围均有活性,最适温度为６０℃,最适ｐＨ值为５．８,底物Ｋｍ值为８７μｇ／ｍＬ。该酶对热和酸碱的稳定性较高,巯基和酪氨酸残基不是该酶活性中心的必需基团。     

A spectrophotometric method for the determination of the kinetic parameters of NH+4 uptake by yeast cells

Abstract The kinetic parameters of NH⁺₄-uptake in yeast cells were determined by a method that is based on the following changes in the external NH⁺₄ concentration in cell suspensions by using NADH-dependent glutamate formation from NH⁺₄ and 2-oxoglutarate. The kinetics of the observed NADH oxidation were analyzed by computer and enabled an estimation of V _max and K _m of the NH⁺₄-uptake system of the cells.     

Kinetic locking-on and auxiliary tactics for bioaffinity purification of NADP+-dependent dehydrogenases using N6-linked immobilized NADP+ derivatives: Studies with mammalian and microbial glutamate dehydrogenases

This study is concerned with the development and application of kinetic locking-on and auxiliary tactics for bioaffinity purification of NADP(+)-dependent dehydrogenases, specifically (1) the synthesis and characterization of highly substituted N(6)-linked immobilized NADP(+) derivatives using a rapid solid-phase modular approach; (2) the evaluation of the N(6)-linked immobilized NADP(+) derivatives for use with the kinetic locking-on strategy for bioaffinity purification of NADP(+)-dependent dehydrogenases: Model bioaffinity chromatographic studies with glutamate dehydrogenase from bovine liver (GDH with dual cofactor specificity, EC 1.4.1.3) and glutamate dehydrogenase from Candida utilis (GDH which is NADP(+)-specific, EC 1.4.1.4); (3) the selection of an effective "stripping ligand" for NADP(+)-dehydrogenase bioaffinity purifications using N(6)-linked immobilized NADP(+) derivatives in the locking-on mode; and (4) the application of the developed bioaffinity chromatographic system to the purification of C. utilis GDH from a crude cellular extract.Results confirm that the newly developed N(6)-linked immobilized NADP(+) derivatives are suitable for the one-step bioaffinity purification of NADP(+)-dependent GDH provided that they are used in the locking-on mode, steps are taken to inhibit alkaline phosphatase activity in crude cellular extracts, and 2',5'-ADP is used as the stripping ligand during chromatography. The general principles described here are supported by a specific sample enzyme purification; the purification of C. utilis GDH to electrophoretic homogeneity in a single bioaffinity chromatographic step (specific activity, 9.12 micromol/min/mg; purification factor, 83.7; yield 88%). The potential for development of analogous bioaffinity systems for other NADP(+)-dependent dehydrogenases is also discussed.     

Successful biological control of mist flower (Ageratina riparia) in New Zealand: Agent establishment, impact and benefits to the native flora

The white smut fungus (Entyloma ageratinae) and the gall fly (Procecidochares alani) were released in New Zealand in 1998 and 2001 respectively to suppress mist flower (Ageratina riparia). The fungus established and spread rapidly, crossing 80 km of sea to Great Barrier Island within 2 years. The mean number of P. alani galls increased exponentially to 1.96/stem at release sites, but dispersal was slow. The impact of the biocontrol agents was monitored once annually from 1998/99 to 2003/04, at up to 51 sites in the North Island. The mean percentage of live leaves infected with fungus rapidly reached nearly 60%. Maximum plant height declined significantly. In heavy infestations, mean percentage cover of mist flower declined from 81 to 1.5%. Galls were only recorded towards the end of the impact study, and at low mean numbers. As mist flower declined, the species richness and mean percentage cover of native plants increased. In contrast, the species richness and mean percentage cover of exotic plants (excluding mist flower) did not change significantly. Many plant species colonizing the plots were important native mid- or late-successional shrubs or trees. With few exceptions, the exotic plant species common in the plots were not weeds that appeared to threaten native forest habitats. There was only a weak “replacement weed effect” from the potentially serious invader African club moss (Selaginella kraussiana). These data, together with reports of reduced threats to rare endemic plants from mist flower, suggest this rapid, well-monitored weed biocontrol program was very successful.     

利用大豆乳清废水生产SCP的研究

以大豆乳清废水为原料,通过对产朊假丝酵母的培养,使大豆乳清废水中的营养成分被酵母菌吸收利用,从而使菌体生长繁殖产生单细胞蛋白。单细胞蛋白(SCP)产量为8.7 mg/mL,蛋白含量为51.3%;且废水COD去除率达到73.4%,达到了国家乳清废水的标准,从而实现了废水资源化利用的目的。     

Enhanced glutathione production by using low-pH stress coupled with cysteine addition in the treatment of high cell density culture of Candida utilis

Aims: To investigate the effects of pH stress coupled with cysteine addition on glutathione (GSH) production in the treatment of high cell density culture of Candida utilis. Methods and Results: We have previously observed that most Candida utilis cells remained viable after being subjected to pH at 1·2 for 3 h and that some intracellular GSH leaked into the medium. A cysteine addition strategy was applied in fed‐batch production of GSH. A single cysteine addition resulted in higher GSH yield than two separate additions without pH stress. An increase in intracellular GSH content triggered inhibition of γ‐glutamylcysteine synthetase (γ‐GCS). A strategy that combines cysteine addition with low‐pH stress was developed to relieve the inhibition of γ‐GCS. Conclusion: Without pH stress, single shot and double shot cysteine addition yielded a total GSH of 1423 and 1325 mg l^?1. In comparison, a low‐pH stress counterpart resulted in a total GSH of 1542 and 1730 mg l^?1, respectively. With low‐pH stress, we observed GSH secretion into the medium at 673 and 558 mg l^?1 and an increase in the γ‐GCS activity by 1·2‐ and 1·5‐fold, respectively. The specific GSH production yield increased from 1·76% to 1·91% (w/w) for single shot, and 1·64% to 2·14% for double shots. Significance and Impact of the Study: Low‐pH shift was applied to alleviate the feedback inhibition of intracellular GSH on γ‐GCS activity by secreting GSH into the medium. This strategy is coupled with cysteine addition to enhance GSH production in Candida utilis.     

Functional response of a parasitoid Ganaspidium utilis （Hymenoptera： Eucoilidae） on the leafminer Liriomyza trifolii （Diptera： Agromyzidae）

Functional response of a solitary, larval-pupal endoparasitoid of Liriomyza leafminers, Ganaspidium utilis Beardsley, was estimated on Liriomyza trifolii Burgess at three temperatures （17℃, 25℃, 29℃ ） and host densities. A type Ⅱ random parasitoid equation （RPE） was used to estimate instantaneous search rate and handling time. The instantaneous search rate increased as temperature increased. All of the RPE regressions obtained for functional response of G. utilis at different temperatures were significant （P〈0.01）. The slope of RPE regression lines was lower across the temperatures. At 29±2℃, the maximum number of larvae parasitized was 7.8 per day. It decreased to 7.2 larvae parasitized at 25±2℃. At 17±2℃, no significant increment of parasitization was observed due to the host density increments. The estimated handling time was lowest at 17±2℃ and highest at 25 ± 2℃, respectively. The ability of G. utilis to find and parasitize L. trifolii over a wide range of temperatures makes them a good candidate for biological control of Liriomyza leafminers.     

Changes in the starvation response through covalent cell attachment

Covalent attachment of Candida utilis cells, possibly simulating natural microbial immobilizations, stimulated stable and significant enhancement of extracellular production of alkaline protease, specifically induced by four different starvation conditions. The enzyme analysis confirmed the identity of the proteases released under all conditions of starvation and no parallel production of other proteolytic enzyme. The enhancement phenomenon as a uniform and stable effect of the whole cell immobilization is discussed in relation to the effect of multipoint, cell-solid surface contact, potentially bringing positive modulations of complex, cellular functions.