己糖转运蛋白在酿酒酵母生长与酒精发酵中的作用

酿酒酵母(Saccharomyces cerevisiae)的生长和发酵与其己糖转运蛋白家族紧密相关.酵母己糖转运蛋白家族包括Hxtlp至Hxt17p、Ga12p、以及同源蛋白Snf3p和Rgt2p这两个葡萄糖感应器.其中Hxt1p～Hxt7p对酵母生长及发酵发挥重要作用,缺失这7个蛋白的酵母无法从培养基中摄取己糖进行生长和发酵.根据对己糖的亲和力的不同,这几个转运蛋白可分为低亲和力转运子.包括Hxt1P和Hxt3p;高亲和力转运子,包括Hxt6p和Hxt7p;以及中等亲和力转运子Hxt2p和Hxt4p;而Hxt5p在生长发酵过程中没有发现有任何诱导表达.本文介绍了Hxt1p-Hxt7p等己糖转运蛋白在酵母生长发酵不同阶段中所发挥的作用,以期为构建高乙醇发酵效率的工业酵母菌株提供参考.     

海藻糖在提高酿酒酵母细胞耐铝性中的作用

海藻糖是一种由两个葡萄糖分子通过,α-α1,1糖苷键连接的非还原性双糖,广泛存在于微生物、动物和植物体内,对生物大分子的活性具有良好的保护效果,对生物体抗逆性起着重要作用。铝是地壳中含量最为丰富的金属元素,是一种严重的环境毒剂,在酸性环境中,对生物生长有重要影响。本文采用酿酒酵母菌株LK及其耐铝突变株LKt,分析它们胞内海藻糖含量的差异,研究铝胁迫下胞内海藻糖的变化。研究结果表明海藻糖含量的提高可明显增加酵母细胞在铝胁迫时的存活率。耐铝突变株LKt在铝胁迫下诱导产生海藻糖的能力显著高于原始菌株LK;酿酒酵母菌株中海藻糖诱导合成积累含量与其耐铝性存在密切正关系,是酵母主要耐铝机制之一。     

Bioremediation of heavy metals in food industry: Application of Saccharomyces cerevisiae

Heavy metals are natural elements in the Earth’s crust that can enter human food through industrial or agricultural processing, in the form of fertilizers and pesticides. These elements are not biodegradable. Some heavy metals are known as pollutants and are toxic, and their bioaccumulation in plant and animal tissues can cause undesirable effects for humans; therefore, their amount in water and food should always be under control. The aim of this study is to investigate the conditions for the bioremediation of heavy metals in foods. Various physical, chemical, and biological methods have been used to reduce the heavy metal content in the environment. During the last decades, bioremediation methods using plants and microorganisms have created interest to researchers for their advantages such as being more specific and environmentally friendly. The main pollutant elements in foods and beverages are lead, cadmium, arsenic, and mercury, which have their own permissible limits. Among the microorganisms that are capable of bioremediation of heavy metals, Saccharomyces cerevisiae is an interesting choice for its special characteristics and being safe for humans, which make it quite common and useful in the food industry. Its mass production as the byproduct of the fermentation industry and the low cost of culture media are the other advantages. The ability of this yeast to remove an individual separated element has also been widely investigated. In countries with high heavy metal pollution in wheat, the use of S. cerevisiae is a native solution for overcoming the problem of solution.This article summarizes the main conditions for heavy metal absorption by S. cerevisiae.How to cite: Massoud R, Hadiani MR, Khosravi Darani K, et al. Bioremediation of heavy metals in food industry: Application of Saccharomyces cerevisiae. Electron J Biotechnol 2019;37. https://doi.org/10.1016/j.ejbt.2018.11.003.     

Adaptive evolution and selection of stress-resistant Saccharomyces cerevisiae for very high-gravity bioethanol fermentation

BackgroundIn industrial yeasts, selection and breeding for resistance to multiple stresses is a focus of current research. The objective of this study was to investigate the tolerance to multiple stresses of Saccharomyces cerevisiae obtained through an adaptive laboratory evolution strategy involving a repeated liquid nitrogen freeze–thaw process coupled with multi-stress shock selection. We also assessed the related resistance mechanisms and very high-gravity (VHG) bioethanol production of this strain.ResultsElite S. cerevisiae strain YF10-5, exhibiting improved VHG fermentation capacity and stress resistance to osmotic pressure and ethanol, was isolated following ten consecutive rounds of liquid nitrogen freeze–thaw treatment followed by plate screening under osmotic and ethanol stress. The ethanol yield of YF10-5 was 16% higher than that of the parent strain during 35% (w/v) glucose fermentation. Furthermore, there was upregulation of three genes (HSP26, HSP30, and HSP104) encoding heat-shock proteins involved in the stress response, one gene (TPS1) involved in the synthesis of trehalose, and three genes (ADH1, HXK1, and PFK1) involved in ethanol metabolism and intracellular trehalose accumulation in YF10-5 yeast cells, indicating increased stress tolerance and fermentative capacity. YF10-5 also showed excellent fermentation performance during the simultaneous saccharification and fermentation of VHG sweet potato mash, producing 13.40% (w/v) ethanol, which corresponded to 93.95% of the theoretical ethanol yield.ConclusionsA multiple-stress-tolerant yeast clone was obtained using adaptive evolution by a freeze–thaw method coupled with stress shock selection. The selected robust yeast strain exhibits potential for bioethanol production through VHG fermentation.How to cite: Zhang Q, Jin Y, Fang Y, et al. Adaptive evolution and selection of stress-resistant Saccharomyces cerevisiae for very high gravity bioethanol fermentation. Electron J Biotechnol 2019;41. https://doi.org/10.1016/j.ejbt.2019.06.003     

Effective diffusion coefficients and bioconversion rates of inhibitory compounds in flocs of Saccharomyces cerevisiae

BackgroundFermentation strategies for bioethanol production that use flocculating Saccharomyces cerevisiae yeast need to account for the mechanism by which inhibitory compounds, generated in the hydrolysis of lignocellulosic materials, are tolerated and detoxified by a yeast floc.ResultsDiffusion coefficients and first-order kinetic bioconversion rate coefficients were measured for three fermentation inhibitory compounds (furfural, hydroxymethylfurfural, and vanillin) in self-aggregated flocs of S. cerevisiae NRRL Y-265. Thièle-type moduli and internal effectiveness factors were obtained by simulating a simple steady-state spherical floc model.ConclusionsThe obtained values for the Thiéle moduli and internal effectiveness factors showed that the bioconversion rate of the inhibitory compounds is the dominant phenomenon over mass transfer inside the flocs.How to cite: Landaeta R, Acevedo F, Aroca G. Effective diffusion coefficients and bioconversion rates of inhibitory compounds in flocs of Saccharomyces cerevisiae. Electron J Biotechnol 2019;42. https://doi.org/10.1016/j.rjbt.2019.08.001     

On the castor dynamic behavior

In this paper, a model describing the castor three-dimensional dynamic behavior, is presented. A procedure, based on the Udwadia-Kalaba formulation has been implemented to write the castor non-linear motion equations. The model takes into account the flexural and lateral compliance of the castor frame and the phenomena related to the wheel rotation. To prescind from the wheel-road interaction parameters, the hypothesis of no sideslip of the wheel has been adopted but other tire models can be easily implemented. The non-linear system stability is evaluated integrating the motion equations and performing a fitting procedure on the natural steering oscillation.     

Expression of antimicrobial peptide Cecropin P1 in Saccharomyces cerevisiae and its antibacterial and antiviral activity in vitro

BackgroundCecropin P1, acting as an antimicrobial, has a broad-spectrum antibacterial activity with some antiviral and antifungal properties. It is a promising natural alternative to antibiotics which is originally isolated from the pig intestinal parasitic nematode Ascaris suum. Many studies have shown that Cecropin P1 is helpful for the prevention or treatment of clinical diseases. Therefore, it is very necessary to establish a safe, nontoxic, and efficient expression method of Cecropin P1.ResultsThe results indicated that the recombinant protein was about 5.5 kDa showed by Tricine–SDS–PAGE and Western blot. And Cecropin P1 was efficiently secreted and expressed after 12 h of induction, with an increasing yield over the course of the induction. Its maximum concentration was 7.83 mg/L after concentration and purification. In addition, in vitro experiments demonstrated that Cecropin P1 not only exerted a strong inhibitory effect on Escherichia coli, Salmonella sp., Shigella sp., and Pasteurella sp., but also displayed an antiviral activity against PRRSV NADC30-Like strain.ConclusionsCollectively, the strategy of expressing Cecropin P1 in Saccharomyces cerevisiae is harmless, efficient, and safe for cells. In addition, the expressed Cecropin P1 has antiviral and antibacterial properties concurrently.How to cite: Jiang R, Zhang P, Wu X, et al., Expression of antimicrobial peptide Cecropin P1 in Saccharomyces cerevisiae and its antibacterial and antiviral activity in vitro. Electron J Biotechnol 2021;50. https://doi.org/10.1016/j.ejbt.2020.12.006     

论西部大开发中的政府行为取向

西部大开发是关中华民族繁荣昌盛的伟大战备决策。从西部大开发的战略意义着手，结合对建国之初的156项基础工程建设和东南沿海改革开放的模式分析，指出在西部开发,政府应以市场机制为基础充分发挥政府的宏观调控作用。     

On the asymptotic behavior of solutions of certain second-order differential equations

In this paper, the second order non-linear differential equation

     

关于政府行为与发展知识经济的关系

此文分析了我国各级政府在发展知识经济———知识产业中应有的定位 ,指出 :政府介入知识经济发展是肯定的 ,最好的办法是用政策、法规设计一种制度 ,使社会生产力诸要素纳入到制度中运行。国外从十二个领域激励、设计社会创新系统 ,并力求保证各项政策“连贯一致地运用 ,达到影响创新的关键性政策要素系统集成” ,这正是本文得出的一个有深刻教益的观念。     

幼儿分享意识及行为培养初探

随着宝宝慢慢的长大,他的自主意识越来越明显,慢慢的显现出一种维护自己利益的表现,那就是拒绝分享,一切都以自己为中心。在家庭教育以及在园的教育的尝试中显试,父母及幼儿园的老师对这种拒绝分享行为的教育干预是有效果的。     

技术创新网络中企业合作动机及合作行为的分析

技术创新网络是由不同合作主体形成的,加入网络的企业具有各自的合作动机,合作动机的差异性直接导致了企业在合作过程中的不同合作行为。在对相关文献梳理的基础上,将网络内企业的合作动机分为效率导向、竞争导向、学习导向与信息导向,并在理论上分析了不同合作动机对合作行为的具体影响。研究对于正确理解技术创新网络中企业的合作行为,制订企业的合作政策具有重要意义。     

论学术批评实名制与科研"恶集富"效应

辞旧迎新的春节前后,举国上下一片欢腾.但在申奥成功、加入世贸、足球出线等等喜庆氛围中,隐隐传来阵阵难以遏拒的"叹息":假冒伪劣、"诚信"危机,足球"黑哨",学术腐败…….正是在这样的社会背景下,中国科学院出台了<中国科学院院士科学道德自律准则>.围绕"准则"的出台,权威人士发表访谈;中央电视台的<经济半小时>节目还独家公布了有关"准则"内部会议的录音.一时间,社会舆论纷纷扬扬,公众传媒见仁见智,各种"看法"、"说法"接踵而来.