Systems metabolic engineering of Corynebacterium glutamicum eliminates all by-products for selective and high-yield production of the platform chemical 5-aminovalerate

5-aminovalerate (AVA) is a platform chemical of substantial commercial value to derive nylon-5 and five-carbon derivatives like δ-valerolactam, 1,5-pentanediol, glutarate, and 5-hydroxyvalerate. Denovo bio-production synthesis of AVA using metabolically engineered cell factories is regarded as exemplary route to provide this chemical in a sustainable way. So far, this route is limited by low titers, rates and yields and suffers from high levels of by-products. To overcome these limitations, we developed a novel family of AVA producing C. glutamicum cell factories. Stepwise optimization included (i) improved AVA biosynthesis by expression balancing of the heterologous davBA genes from P. putida, (ii) reduced formation of the by-product glutarate by disruption of the catabolic y-aminobutyrate pathway (iii), increased AVA export, and (iv) reduced AVA re-import via native and heterologous transporters to account for the accumulation of intracellular AVA up to 300 mM. Strain C. glutamicum AVA-5A, obtained after several optimization rounds, produced 48.3 g L-1 AVA in a fed-batch process and achieved a high yield of 0.21 g g-1. Surprisingly in later stages, the mutant suddenly accumulated glutarate to an extent equivalent to 30% of the amount of AVA formed, tenfold more than in the early process, displaying a severe drawback toward industrial production. Further exploration led to the discovery that ArgD, naturally aminating N-acetyl-l-ornithine during l-arginine biosynthesis, exhibits deaminating side activity on AVA towards glutarate formation. This promiscuity became relevant because of the high intracellular AVA level and the fact that ArgD became unoccupied with the gradually stronger switch-off of anabolism during production. Glutarate formation was favorably abolished in the advanced strains AVA-6A, AVA-6B, and AVA-7, all lacking argD. In a fed-batch process, C. glutamicum AVA-7 produced 46.5 g L-1 AVA at a yield of 0.34 g g-1 and a maximum productivity of 1.52 g L-1 h-1, outperforming all previously reported efforts and stetting a milestone toward industrial manufacturing of AVA. Notably, the novel cell factories are fully genome-based, offering high genetic stability and requiring no selection markers

“We Need a Big Revolution in Email Advertising”: Users’ Perception of Persuasion in Permission-based Advertising Emails

Persuasive tactics intend to encourage users to open advertising emails. However, these tactics can overwhelm users, which makes them frustrated and leads to lower open rates. This paper intends to understand which persuasive tactics are used and how they are perceived by users. We first developed a categorization of inbox-level persuasive tactics in permission-based advertising emails. We then asked participants to interact with an email inbox prototype, combined with interviews (N=32), to investigate their opinions towards advertising emails and underlying persuasive tactics. Our qualitative findings reveal poor user experience with advertising emails, which was related to feeling surveilled by companies, forced subscriptions, high prior knowledge about persuasive tactics, and a desire for more agency. We also found that using certain persuasive tactics on the inbox level is perceived as ethically inappropriate. Based on these insights, we provide design recommendations to improve advertising communication and make such emails more valuable to users

A bio-based route to the carbon-5 chemical glutaric acid and to bionylon-6,5 using metabolically engineered Corynebacterium glutamicum

In the present work, we established the bio-based production of glutarate, a carbon-5 dicarboxylic acid with recognized value for commercial plastics and other applications, using metabolically engineered Corynebacterium glutamicum. The mutant C. glutamicum AVA-2 served as a starting point for strain development, because it secreted small amounts of glutarate as a consequence of its engineered 5-aminovalerate pathway. Starting from AVA-2, we overexpressed 5-aminovalerate transaminase (gabT) and glutarate semialdehyde dehydrogenase (gabD) under the control of the constitutive tuf promoter to convert 5-aminovalerate further to glutarate. The created strain GTA-1 formed glutarate as a major product, but still secreted 5-aminovalerate as well. This bottleneck was tackled at the level of 5-aminovalerate re-import. The advanced strain GTA-4 overexpressed the newly discovered 5-aminovalerate importer NCgl0464 and formed glutarate from glucose in a yield of 0.27 mol mol−1. In a fed-batch process, GTA-4 produced more than 90 g L−1 glutarate from glucose and molasses based sugars in a yield of up to 0.70 mol mol−1 and a maximum productivity of 1.8 g L−1 h−1, while 5-aminovalerate was no longer secreted. The bio-based glutaric acid was purified to >99.9% purity. Interfacial polymerization and melt polymerization with hexamethylenediamine yielded bionylon-6,5, a polyamide with a unique structure

The effects of privacy-non-invasive interventions on cheating prevention and user experience in unproctored online assessments: An empirical study

peer reviewedPreventing cheating without invading test-takers’ privacy in high-stakes online summative assessments poses a challenge, especially when the assessment is remote and unproctored. We conducted a between-subjects experiment (N = 997) in a realistic online test simulation to investigate the effects of three privacy-non-invasive anti-cheating interventions (honor code reminder, warning message, and monitoring message) on cheating prevention from a user-centered perspective. The quantitative results indicated that, compared to a control condition, displaying a honor code reminder during an online test worked best in lowering the odds of cheating. None of the interventions affected user experience and test-taking self-efficacy significantly. Further open-ended questions revealed that interventions can cause distraction which in turn could potentially evoke negative emotions. The decision to cheat was influenced by the extent to which interventions conveyed that cheating is wrong and also by test-takers’ perception of getting caught if they cheated. We derived recommendations for a fair and cheating-preventive unproctored online assessment for researchers and practitioners

Creating positive learning experiences with technology: A field study on the effects of user experience for digital concept mapping

Learning and assessment are increasingly mediated by digital technologies. Thus, learners’ experiences with these digital technologies are growing in importance, as they might affect learning and assessment. The present paper explores the impact of user experience on digital concept mapping. It builds on user experience theory to explain variance in the intention to use digital concept mapping tools and in concept map-based assessment scores. Furthermore, it identifies fulfillment of psychological needs as an important driver of positive experiences. In a field study in three schools and a university (N = 71), we tested two concept mapping prototypes on computers and tablets. We found that user experience is a significant factor explaining variance in intention to use. User experience also explained variance in three out of four concept mapping scores on tablets, potentially related to the lower pragmatic quality of the tablet prototypes. Fulfillment of psychological needs strongly affected perceptions of different qualities of user experience with digital concept mapping. These results indicate that user experience needs to be considered in digital concept mapping to provide a positive and successful environment for learning and assessment. Finally, we discuss implications for designers of digital learning and assessment tools

"Do we need an entire course about it?": Evaluating two years of teaching HCI in computer science

Educators increasingly agree on the importance of teaching Human-Computer Interaction (HCI) to Computer Science (CS) students, but there is debate on how to best integrate HCI into CS curricula. Unfortunately, standard course evaluations typically do not provide sufficient insights for improving HCI classes. In the present article, we used a human-centered design approach to evaluate our HCI classes, building on a qualitative study with CS students from four introductory HCI classes over two years. We report on a qualitative assessment through interviews, photo elicitation and sentence completion. Specifically, we addressed four research questions: which contents were the most relevant, how students experienced the courses, how they view the role of HCI in CS, and which outcomes they perceived from the HCI courses. We gathered rich qualitative insights beyond the standard course evaluations and derived concrete enhancements for future course iterations. We discuss implications for other HCI educators and contribute recommendations for the living HCI curriculum. Furthermore, we reflect on the usefulness of our methodological approach to collect in-depth constructive feedback from students

Measuring discomfort from glare: recommendations for good practice

This article presents a review of the methods used for subjective evaluation of discomfort from glare, focusing on the two procedures most frequently used in past research – adjustment and category rating. Evidence is presented to demonstrate that some aspects of these procedures influence the evaluation, such as the range of glare source luminances available in an adjustment procedure, leading to biased evaluations and which hence reduce the reliability and validity of the data. The article offers recommendations for good practice when using these procedures and also suggests alternative methods that might be explored in further work

Qualitative methods to explore thermo-spatial perception in outdoor urban spaces

To be able to design thermally comfortable urban spaces, designers require design guidelines that respond to people's thermal and spatial perception. This thermo-spatial perception is influenced by a range of dimensions: the nature and scale of spatial contexts, the kinetic state of the people and the time scale of their perception ('now' or 'the past'). Recently, novel qualitative methods have been developed to link thermal and spatial information of people's perception. To attain an overview of these methods we conducted an extensive literature review. The results show that these qualitative methods respond to the different dimensions by combinations of momentary and long-term thermal perception research in stationary mode and in motion in varying spatial environments. These qualitative methods deliver explicit combination of thermal and spatial information. Based on that evidence, new knowledge relevant to urban design of thermally comfortable urban spaces can be generated

A review of the corrective power of personal comfort systems in non-neutral ambient environments

This paper discusses a spectrum of systems that cool or heat occupants personally, termed ‘personal comfort systems’ (PCS), in order to quantify their ability to produce comfort in ambient temperatures that are above or below the subjects’ neutral temperatures.The comfort-producing effectiveness may be quantified in terms of a temperature difference, coining the index ‘corrective power’ (CP). CP is defined as difference between two ambient temperatures at which equal thermal sensation is achieved - one with no PCS (the reference condition), and one with PCS in use.  CP represents the degree to which a PCS system may “correct” the ambient temperature toward neutrality. CP can alternatively be expressed in terms of thermal sensation and comfort survey scale units.Published studies of PCS are reviewed to extract their CP values. Cooling CP ranges from -1 to -6K, and heating CP from 2K to 10K.  The physical characteristics of the particular PCS systems are not reported in detail here, but are presented as prototypes of what is possible.  Deeper understanding of PCS will require new physiological and psychological information about comfort in local body segments and subsegments, and about spatial and temporal alliesthesia.  These topics present many opportunities for productive future research