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

《Electronic Journal of Biotechnology》2021

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.  相似文献   

Reexamining Fear Appeal Models from Cognitive Appraisal Theory and Functional Emotion Theory Perspectives     

Jiyeon So  Kai Kuang  Hyunyi Cho 《Communication monographs》2016,83(1):120-144

Recognizing inconsistencies between the extant fear appeal theories and emotion literature, this research integrated cognitive appraisal theory and functional emotion theory into a fear appeal literature and proposed a model that describes a process through which both fear and anxiety can contribute to adaptive responses. Findings from an experiment (N = 927) supported the predictions. Fear and anxiety emerged as distinct constructs. Perceived susceptibility was a stronger predictor of anxiety than fear, while perceived severity was a stronger predictor of fear than anxiety. In addition, greater fear and anxiety led to greater response efficacy through increased motivation to obtain protection-related information and heightened attention to such information, thus mediating the threat and coping appraisal processes. The SEM model testing the predictions showed that perceived susceptibility had the strongest total effects on protection intention, followed by anxiety, perceived severity, and fear.  相似文献   

电力变压器绕组变形的测试     

丰伟  黄问贵 《九江职业技术学院学报》2011,(2):15-16

通过试验手段对受冲击后的变压器内部线圈绕组受损情况进行检测,对于正确引导变压器的检修,有效地减少设备停电时间具有极其重要的现实意义。同时,对于变压器的检测提供可行的变压器测试方法,以及判断变压器是否适合重新投入运行、投入后是否存在事故隐患。  相似文献   

Effective extraction of elastase from Bacillus sp. fermentation broth using aqueous two-phase system   总被引：1，自引：0，他引：1  

Xu Y  He GQ  Li JJ 《Journal of Zhejiang University. Science. B》2005,6(11):1087-1094

INTRODUCTION Aqueous two-phase system (ATPS) is widely used in biochemistry and biotechnology for purifica- tion of proteins (Diamond and Hsu, 1992; Balasubramaniam et al., 2003), enzymes (Pan et al., 2001; Bim and Franco, 2000), amino acids (Li et al., 2002), antibiotics (Yang et al., 1994; Guan et al., 1994), nucleic acids (Ohlsson et al., 1978; Kimura, 2000), aroma compounds (Marco et al., 2000) and lactic acid (Planas et al., 1998). ATPS is mainly composed of two-incompatible p…  相似文献   

基于等级反应模型的CAT系统的研究和开发     

周婕  陈平  丁树良 《考试研究》2005,(3)

计算机化自适应测验是现代测验研究中的一个重要领域,而目前大多研究都基于0-1评分模型,适用范围不广。本文对Samejima等级反应模型进行探讨和研究,运用DELPHI开发研制多级评分计算机化自适应测验。  相似文献   

Application of response surface methodology in medium optimization for pyruvic acid production of <Emphasis Type="Italic">Torulopsis glabrata</Emphasis> TP19 in batch fermentation     

Zhang J  Gao NF 《Journal of Zhejiang University. Science. B》2007,8(2):98-104

Response surface methodology （RSM） was used to optimize the fermentation medium for enhancing pyruvic acid production by Torulopsis glabrata TP19. In the first step of optimization, with Plackett-Burman design, ammonium sulfate, glucose and nicotinic acid were found to be the important factors affecting pyruvic acid production significantly. In the second step, a 23 full factorial central composite design and RSM were applied to determine the optimal concentration of each significant variable. A second-order polynomial was determined by the multiple regression analysis of the experimental data. The optimum values for the critical components were obtained as follows： ammonium sulfate 0.7498 （10.75 g/L）, glucose 0.9383 （109.38 g/L） and nicotinic acid 0.3633 （7.86 mg/L） with a predicted value of maximum pyruvic acid production of 42.2 g/L. Under the optimal conditions, the practical pyruvic acid production was 42.4 g/L. The determination coefficient （R^2） was 0.9483, which ensures adequate credibility of the model. By scaling up fermentation from flask to jar fermentor, we obtained promising results.  相似文献   

Development and Validation of a Multimedia-based Assessment of Scientific Inquiry Abilities     

Che-Yu Kuo  Tsung-Hau Jen  Ying-Shao Hsu 《International Journal of Science Education》2013,35(14):2326-2357

The potential of computer-based assessments for capturing complex learning outcomes has been discussed; however, relatively little is understood about how to leverage such potential for summative and accountability purposes. The aim of this study is to develop and validate a multimedia-based assessment of scientific inquiry abilities (MASIA) to cover a more comprehensive construct of inquiry abilities and target secondary school students in different grades while this potential is leveraged. We implemented five steps derived from the construct modeling approach to design MASIA. During the implementation, multiple sources of evidence were collected in the steps of pilot testing and Rasch modeling to support the validity of MASIA. Particularly, through the participation of 1,066 8th and 11th graders, MASIA showed satisfactory psychometric properties to discriminate students with different levels of inquiry abilities in 101 items in 29 tasks when Rasch models were applied. Additionally, the Wright map indicated that MASIA offered accurate information about students’ inquiry abilities because of the comparability of the distributions of student abilities and item difficulties. The analysis results also suggested that MASIA offered precise measures of inquiry abilities when the components (questioning, experimenting, analyzing, and explaining) were regarded as a coherent construct. Finally, the increased mean difficulty thresholds of item responses along with three performance levels across all sub-abilities supported the alignment between our scoring rubrics and our inquiry framework. Together with other sources of validity in the pilot testing, the results offered evidence to support the validity of MASIA.  相似文献   

The effects of Success for All in the Netherlands on the reading achievement of first-grade students at risk of reading problems     

《Studies in Educational Evaluation》2023

This article reports outcomes of a quasi-experimental evaluation of Success for All (SfA), a comprehensive school reform program that has recently been introduced in the Netherlands. The Response to Intervention framework is used to describe how SfA supports students at different Tiers. The effects of SfA on five reading subskills were investigated for first-grade students at risk of reading problems. 299 students from two different cohorts were involved. Multilevel analyses demonstrated a significant effect of SfA on reading comprehension (ES = +0.26) in the first cohort. For the second cohort and the other reading subskills, mostly small positive effects of SfA were found, though these effects were not statistically significant. Furthermore, the relationship between tutoring intensity and reading achievement was examined. In the second cohort, a significant negative association of tutoring intensity with word and text reading skills was found. Implementation issues that may have impacted the outcomes are discussed.  相似文献   

The Integration of Common Core and Response to Intervention: Supporting Vulnerable Readers in a Time of Sophisticated Standards     

Elizabeth L. Jaeger  P. David Pearson 《The Educational forum》2017,81(1):92-107

The Common Core State Standards and Response to Intervention are significant contemporary educational initiatives that have emerged largely in isolation from one another. We argue that an integration of these initiatives is beneficial. We trace the independent development of these two initiatives and offer suggestions for how they might fruitfully transact, fully supporting vulnerable readers in their efforts to master sophisticated standards. Results from a school implementing these initiatives as an integrated whole are discussed.  相似文献   

《野草》的互文性探究     

陈贺兰 《福建师范大学学报(哲学社会科学版)》2011,(6)

《野草》的互文性文本可划分成五种不同类型。互文作为一种表现手法,其具体实现途径多种多样,可交替使用。互文源自两个相似灵魂的必然靠近,鲁迅与尼采的生命共感召唤出作品中一系列相近的意象。从互文手法在鲁迅作品中的演变可以窥见鲁迅心境的变化。  相似文献