在线推定和控制葡萄糖浓度改善谷氨酸发酵性能

谷氨酸发酵过程一般需要定时、人工分批式地添加葡萄糖。该流加操作方式会引起发酵罐内葡萄糖浓度的剧烈波动, 不利于高效、稳定的谷氨酸生产。谷氨酸发酵具有显著的非增殖耦联特征, 产酸期葡萄糖耗量与氨水耗量存在非常明显的关联性。通过在线计量氨水耗量推定糖耗以及葡萄糖浓度, 可比较准确地将谷氨酸发酵产酸期的糖浓度控制在预先设定的水平。当糖浓度控制在5 g/L~10 g/L的低水平时, 最终谷氨酸浓度可以达到80 g/L的较高水平, 高糖浓度下的渗透压效应有望得到缓解, 有利于发酵生产的稳定。     

发酵工艺条件的多目标优化

以模糊综合评价值作为评价指标、加权单纯形方法优化发酵过程工艺条件。应用本方法,对以谷氨酸发酵废液为原料的酵母发酵过程的发酵温度、ｐＨ、菌种量、初始糖浓度、通气量及流加液糖浓度等工艺条件进行了优化。     

利用甜菜糖蜜发酵生产L-谷氨酸的中间试验

随着味精工业的日益发展,发酵生产L-谷氨酸的工业用粮不断增加。为开辟L-谷氨酸发酵的原料来源,扩大甜菜糖蜜综合利用的范围,我们遵照毛主席关于“备战、备荒、为人民”的教导,在党的一元化领导下,组成了以工人为主体的试验小组,进行了用甜菜糖蜜代替淀粉水解糖发酵生产L-谷氨酸的试验工作,通过     

基于pH的反馈补料方法在谷氨酸发酵中的应用

为简化谷氨酸发酵补料工艺,提出了一种新型的基于pH的补料方式。考察谷氨酸发酵过程中氨消耗量 (x) 和糖消耗量 (y) 发现,两者之间存在较好的线性关系 (y=7.4744x,R2=0.9989),以此为pH反馈补料工艺中补料液中葡萄糖与氨的混合比例,能较好地将谷氨酸发酵过程中葡萄糖浓度稳定在12~21 g/L。比较恒定葡萄糖浓度补料工艺与pH反馈补料工艺发现,采用pH反馈补料工艺进行发酵,葡萄糖转化率、谷氨酸产酸速率分别提高了9.06％和17.5％左右,同时发酵周期缩短2 h以上。     

谷氨酸产生菌FM820-7菌株一次性中糖发酵的研究

自木下等人首先报导谷氨酸发酵工程的研究工作以来,已有很大发展。采用以糖蜜为原料的低糖流加技术进行生产,能得到较好的产酸率。但是由于各种因素的限制,绝大多数厂家还不能采用这一技术。为提高谷氨酸的发酵水平,目前我国的生产厂都正从低糖发酵向中糖发酵过     

一次高糖谷氨酸发酵提高转化率的探讨

味精生产的实践已证明,随着初始糖浓度的提高,转化率反而降低。这是目前味精生产初糖浓度不高(10～15％),设备利用率较低的主要原回。为改变这种落后状态,有些生产厂和科研单位对菌种进行诱变和工艺条件进行改良,均取得一定的效果。沈阳味精厂在500升和5万升发酵罐试验成功的低糖连续流加新工艺,为我国味精工业生产闯出新路,做出了新贡献。尽管如此,对一次高糖(18—20％)发酵研究较少,而一次高糖发酵工艺简单,是味精生产的发展方向。本文论述了由于提高了糖的浓度引起的谷氨酸产生糖生理特性的变化及对谷氨酸生物合成成的影响。探讨了随着糖浓度的提高,转化率反而突而降低的主要原因,为有目的选育谷氨酸产生菌突变株提供了一条新途     

由β-型谷氨酸转化为α-型谷氨酸的方法

在谷氨酸的微生物发酵和提取过程中,如果生产工艺条件控制不当,常因发酵染菌,酮酸过高、残糖高或中和速度快,温度高等因素导致形成β-氨基戊二酸(即β-型谷氨酸),使味精生     

关于谷氨酸高产菌WTH-1菌的选育

近年来,我国味精生产发展很快,已达到相当规模。国外采用一次高糖或低糖流加工艺路线,使发酵产酸率和转化率提高。本试验以北京棒杆菌AS.1.299为亲株,经紫外线、通电、硫酸二乙酯以及氯化锂等复合诱变处理,定向选育耐高糖、耐高谷氨酸、不利用谷氨酸与抗     

谷氨酸发酵过程葡萄糖自动流加系统

补料（流加葡萄糖）操作是谷氨酸发酵过程最重要的操作之一,工业上有各种各样的补料操作方法。控制葡萄糖浓度于一个较为平稳且适中的水平有利于提高谷氨酸发酵的性能指标。通过在线计量谷氨酸发酵中的氨水耗量并据此在线推定发酵液中的葡萄糖浓度,构建了一个谷氨酸发酵自动在线补料系统。使用该控制系统,谷氨酸发酵过程的葡萄糖浓度可以控制在任意水平,平稳、无波动的谷氨酸发酵可以得到实现。     

浓糖谷氨酸发酵试验

目前,国内一般采用10%或13%的初始糖进行L-谷氨酸发酵生产。为了进一步提高发酵产酸率、提取收得率及设备利用率,我们采用加大种子量及发酵中途补加糖液的方法,分别在500升及20,000升发酵罐进行了中试及扩大试验,都取得了很好的效果。采用5%种子量,补加糖液后总糖达15%左右,产酸率在6.0—6.5%左右,转化率为40%左右,发酵周期40     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.