Development of a chemically defined medium for Planctopirus limnophila to increase biomass production

BackgroundPlanctomycetes is a phylum of biofilm-forming bacteria with numerous biosynthetic gene clusters, offering a promising source of new bioactive secondary metabolites. However, the current generation of chemically defined media achieves only low biomass yields, hindering research on these species. We therefore developed a chemically defined medium for the model organism Planctopirus limnophila to increase biomass production.ResultsWe found that P. limnophila grows best with a 10 mM sodium phosphate buffer. The replacement of complex nitrogen sources with defined amino acid solutions did not inhibit growth. Screening for vitamin requirements revealed that only cyanocobalamin (B12) is needed for growth. We used response surface methodology to optimize the medium, resulting in concentrations of 10 g/L glucose, 34 mL/L Hutner’s basal salts, 23.18 mM KNO₃, 2.318 mM NH₄Cl and 0.02 mg/L cyanocobalamin. The analysis of amino acid consumption allowed us to develop a customized amino acid solution lacking six of the amino acids present in Aminoplasmal 10%. Fed-batch cultivation in a bioreactor using the optimized medium achieved a final ΔOD₆₀₀ of 46.8 ± 0.5 after 108 h, corresponding to a cell dry weight of 13.6 ± 0.7 g/L.ConclusionsThe optimized chemically defined medium allowed us to produce larger amounts of biomass more quickly than reported in earlier studies. Further research should focus on triggering P. limnophila biofilm formation to activate the gene clusters responsible for secondary metabolism.How to cite: Kruppa OC, Gerlach D, Fan R, et al. Development of a chemically defined medium for Planctopirus limnophila to increase biomass production. Electron J Biotechnol 2021;54. https://doi.org/10.1016/j.ejbt.2021.09.002.     

对机关事业单位养老保险改革的思考

一直以来遭受口诛笔伐的养老金双轨制终被废除,伴随着机关事业单位养老保险的改革,养老金制度取得了里程碑式的进步。但并轨后,退休金差别却"涛声依旧",公务员职业年金的建立掀起了大众关于养老金公平又一轮的争议。巨大的转制成本、三大风险的应对,都是养老金改革亟待解决的问题。如何顺利推进改革,完善政策措施,我们可以结合本国国情,借鉴国际经验,推迟退休年龄。同时引入弹性退休制,建立名义账户制,实行延期福利,促进企业年金的广覆盖,建立多层次养老保险制度,实现公平和效率以及养老制度可持续发展。     

Does the Great Firewall Really Isolate the Chinese? Integrating Access Blockage With Cultural Factors to Explain Web User Behavior

The dominant understanding of Internet censorship posits that blocking access to foreign-based websites creates isolated communities of Internet users. We question this discourse for its assumption that if given access people would use all websites. We develop a conceptual framework that integrates access blockage with social structures to explain Web users’ choices, and argue that users visit websites they find culturally proximate and that access blockage matters only when such sites are blocked. We examine the case of China, where online blockage is notoriously comprehensive, and compare Chinese Web usage patterns with those elsewhere. Analyzing audience traffic among the 1000 most visited websites, we find that websites cluster according to language and geography. Chinese websites constitute one cluster, which resembles other such geolinguistic clusters in terms of both its composition and its degree of isolation. Our sociological investigation reveals a greater role of cultural proximity than access blockage in explaining online behaviors.     

当代西方文学思潮的界定

本文以当代西方文学为研究对象,通过深入的理论梳理来探究其在时空维度上的界定,认为1968年不仅是一个界定当代西方的重要时间节点,同时也是当代西方文学思潮起始之点,现实主义文学思潮、存在主义文学思潮、新左派与反文化文学思潮、后殖民主义文学思潮、女性主义文学思潮、流行文化文学思潮、生态主义文学思潮以及实验主义文学思潮便是其中最为突出的代表。这些文学思潮归根结底是当代西方资本主义经济基础、社会存在的反映,同时又是文学作为意识形态形式用审美特殊性探寻社会出路、寻找人的生存的新的可能性的文化心声。     

浙派研究综述

本文回顾了迄今为止浙派的研究情况,从浙派的界定、相关论争、浙派与清代文化的关系及浙派诗人与派系研究三个方面,总结至今在浙派研究方面所取得的成就,并试图为深化该领域的研究略陈管见。     

养老金会计的国际比较与启示

随着社会的不断发展与进步,人口的老龄化问题日益严重。在我国已进入老龄化社会的同时,国内对企业养老金会计的研究多还停留在对发达国家及其企业的养老金会计处理的介绍阶段,缺乏对企业养老金会计理论与实务的研究,这使得如何完善养老保险体制成为政府、企业和个人等多方关注的焦点。本文介绍养老金会计的基本框架,导入国外先进的养老金会计模式,旨在对中国的养老金会计改革提供参考。     

有限责任公司股东出资转让行为论析

我国公司法第35条沿袭传统公司立法精神,对有限责任公司股东向非股东的第三人转让出资设置了两项限制条件,其立法价值需要重估。立法中规定的全体股东过半数同意无法真正起到制约股东向第三人转让出资的作用。其他股东的优先购买权也不能对抗转让出资的股东与第三人的出资转让行为。     

醉驾入刑的实践困境阐释

醉驾入刑后,在实践中面临着诸多困境.首先,国家治理能力低下导致了选择性司法的不可避免,进而使我国本已有限的司法权威更加弱化.其次,侦查主体角色的混乱,证据标准的不合理,诉讼期间的不合理缩短都对刑事程序法的实施构成了破坏.再次,入罪标准的降低,将使更多的人背负罪犯恶名,从而对他们的生活产生巨大影响,有可能促使更多的人犯罪.此外,罪驾入刑的实施,将对制酒、餐饮以及娱乐等行业的正常经营构成冲击.所以,我们应该严守犯罪圈的界限,坚持刑法的谦抑性,当能够通过现有立法对醉酒驾驶进行治理时,就坚决不单独适用刑罚的手段.     

论不纯正不作为犯的作为义务的司法认定

目前我国的刑事立法并没有对不纯正的不作为犯作出明确的规定,但是在刑事司法实践中却对不纯正的不作为犯进行定罪处刑,这种矛盾造成了立法与司法的脱节。而解决这个矛盾的关键就在于对不纯正不作为犯的作为义务进行精准的界定,对其作为义务的范围规定的过宽,有可能导致刑法的泛化和刑罚的膨胀,有损刑法的谦抑性原则;反之,对作为义务的界定过窄,则使刑法的处罚范围过小,有损刑法的法益保护机能。因此,科学、准确的明晰不纯正不作为犯的作为义务,对我国的刑事理论和刑事司法都大有裨益。     

从刑法的谦抑性和效益、公正价值看醉驾入罪

刑法的谦抑性指的是只有在立法机关认为某一规范必不可少,确实没有其他更好的可以替代刑罚的方法存在的情况下,才能将某种违反法律秩序的行为规定为犯罪行为。从刑法的谦抑性原理分析,醉驾入罪不具有可行性和必要性;从刑法追求的效益和公正价值分析,其不能满足效益和公正价值的内在要求。因此,醉驾行为不应当被规定为犯罪。