Research outputs from Pure / Zinātniskās darbības rezultāti no ZDIS Pure

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Streptococcus pneumoniae serotypes and factors associated with antimicrobial resistance in Invasive pneumococcal disease cases in Latvia, 2012–2022
(2025-03-12) Savrasova, Larisa; Villeruša, Anita; Zeltiņa, Indra; Krūmiņa, Angelika; Čupeca, Hedija; Balasegaram, Sooria; Grēve, Māra; Savicka, Oksana; Selderina, Solvita; Galajeva, Jelena; Dushacka, Diana; Institute of Public Health; Department of Infectology; Department of Human Physiology and Biochemistry; Statistics Unit
Background: Streptococcus pneumoniae is a major cause of Invasive pneumococcal disease (IPD), including bacteremic pneumonia, septicemia, and meningitis. The introduction of pneumococcal conjugate vaccines (PCVs) has significantly reduced the incidence of IPD caused by vaccine-covered serotypes. However, serotype replacement and antimicrobial resistance remain concerns. In Latvia, vaccination against pneumococcal disease was introduced into the NIP in 2010 with PCV7, later transitioning to PCV10 in 2012 and to PCV15 in 2024. This study aims is to determine the changes in S. pneumoniae antimicrobial resistance and its association with PCV10 serotypes in Latvia. Materials and methods: We conducted a population-based cross-sectional study using IPD surveillance data from Latvia over an 11-year period (2012–2022). IPD cases were defined according to the European Union case definition. Serotyping and antimicrobial susceptibility testing were performed on isolates from normally sterile sites. We analyzed the differences in IPD incidence, serotype distribution, and antimicrobial resistance using chi-square tests and multivariable logistic regression was used to determine associations between antimicrobial resistance and risk factors. Results: A total of 811 IPD cases were reported, with significant differences observed across the study period (p < 0.001). The most common serotypes were 3 and 19A. The proportion of IPD cases caused by PCV10 serotypes significantly decreased over the years, while cases caused by PCV13, PCV15, and PPPV23 serotypes increased. Antimicrobial susceptibility testing revealed resistance rates of 3.8% to penicillin, 5.4% to erythromycin, and 1.2% to cefotaxime/ceftriaxone. Erythromycin resistance showed significant variation over time (p = 0.016), decreasing from 7.1% in 2012 to 4.8% in 2022. Multivariable logistic regression indicated that IPD cases with S. pneumoniae PCV10 serotypes and meningitis were significantly associated with an increased likelihood of penicillin and erythromycin resistance. Conclusion: The study highlights a decrease in erythromycin resistance in IPD cases over time and significant associations between PCV10 serotypes and meningitis in IPD cases and penicillin and erythromycin resistance. The findings underscore the importance of continuous surveillance of S. pneumoniae serotypes and antimicrobial resistance patterns to inform treatment guidelines and vaccination policies. Further research is needed to assess the long-term impact of the PCV15 vaccine on S. pneumoniae serotype distribution and resistance.
Mandibular chondroblastic type osteosarcoma primarily diagnosed as chondrosarcoma as a result of radiation therapy : a case report
(2025-03) Rone, Alise Elizabete; Bāgante, Ieva; Vasilcenko, Irina; Zariņš, Jānis; Deksnis, Renārs; Hasnere, Sigita; Department of Oral and Maxillofacial Surgery and Oral Medicine
Radiation therapy is a recognized etiological factor for osteomyelitis, osteoradionecrosis and multiple sarcomas such as chondrosarcoma and osteosarcoma. Here we present a case of mandibular chondroblastic type osteosarcoma induced by radiotherapy which was primarily misdiagnosed as chondrosarcoma. A female presented with main complaint of pain at the extraction site following multiple teeth extraction and sequestrectomy on the right lower jaw. Medical history revealed stage IV squamous cell carcinoma of the base of the tongue which was treated by surgical excision, chemotherapy and radiotherapy ten years ago. Four recurring sequestrectomies were performed, but only histological material from the fourth sequestrectomy revealed grade 2 chondrosarcoma. This was followed by resection of the tumour and floor of the mouth, mandibular, lip and facial skin reconstruction and operation material through histology was again confirmed to be grade 2 chondrosarcomas. In a year’s time, pathological nodule in thyroid gland was found on CT, surgery was performed. Operation material now revealed high grade chondroblastic type osteosarcoma and additional radiotherapy and chemotherapy was prescribed. This case illustrated chondrosarcoma and chondroblastic type osteosarcoma as a rare malignant incidence, with diagnostical difficulties and treatment. Differential diagnosis should be considered if no positive changes are observed after the designated therapy as well as importance of immunohistological evaluation. One treated malignancy does not exclude development of another unrelated malignancy.
TRFBA : An algorithm to integrate genome-scale metabolic and transcriptional regulatory networks with incorporation of expression data
(2017-04-01) Motamedian, Ehsan; Mohammadi, Maryam; Shojaosadati, Seyed Abbas; Heydari, Mona
Motivation: Integration of different biological networks and data-types has been a major challenge in systems biology. The present study introduces the transcriptional regulated flux balance analysis (TRFBA) algorithm that integrates transcriptional regulatory and metabolic models using a set of expression data for various perturbations. Results: TRFBA considers the expression levels of genes as a new continuous variable and introduces two new linear constraints. The first constraint limits the rate of reaction(s) supported by a metabolic gene using a constant parameter (C) that converts the expression levels to the upper bounds of the reactions. Considering the concept of constraint-based modeling, the second set of constraints correlates the expression level of each target gene with that of its regulating genes. A set of constraints and binary variables was also added to prevent the second set of constraints from overlapping. TRFBA was implemented on Escherichia coli and Saccharomyces cerevisiae models to estimate growth rates under various environmental and genetic perturbations. The error sensitivity to the algorithm parameter was evaluated to find the best value of C. The results indicate a significant improvement in the quantitative prediction of growth in comparison with previously presented algorithms. The robustness of the algorithm to change in the expression data and the regulatory network was tested to evaluate the effect of noisy and incomplete data. Furthermore, the use of added constraints for perturbations without their gene expression profile demonstrates that these constraints can be applied to improve the growth prediction of FBA. Availability and Implementation: TRFBA is implemented in Matlab software and requires COBRA toolbox. Source code is freely available at http://sbme.modares.ac.ir.
A benchmark-driven approach to reconstruct metabolic networks for studying cancer metabolism
(2019) Jamialahmadi, Oveis; Hashemi-Najafabadi, Sameereh; Motamedian, Ehsan; Romeo, Stefano; Bagheri, Fatemeh
Genome-scale metabolic modeling has emerged as a promising way to study the metabolic alterations underlying cancer by identifying novel drug targets and biomarkers. To date, several computational methods have been developed to integrate high-throughput data with existing human metabolic reconstructions to generate context-specific cancer metabolic models. Despite a number of studies focusing on benchmarking the context-specific algorithms, no quantitative assessment has been made to compare the predictive performance of these methods. Here, we integrated various and different datasets used in previous works to design a quantitative platform to examine functional and consistency performance of several existing genome-scale cancer modeling approaches. Next, we used the results obtained here to develop a method for the reconstruction of context-specific metabolic models. We then compared the predictive power and consistency of networks generated by our method to other computational approaches investigated here. Our results showed a satisfactory performance of the developed method in most of the benchmarks. This benchmarking platform is of particular use in algorithm selection and assessing the performance of newly developed algorithms. More importantly, it can serve as guidelines for designing and developing new methods focusing on weaknesses and strengths of existing algorithms.
Adapting Classification Neural Network Architectures for Medical Image Segmentation Using Explainable AI
(2025-02-13) Nikulins, Arturs; Edelmers, Edgars; Sudars, Kaspars; Polaka, Inese; Faculty of Medicine
Segmentation neural networks are widely used in medical imaging to identify anomalies that may impact patient health. Despite their effectiveness, these networks face significant challenges, including the need for extensive annotated patient data, time-consuming manual segmentation processes and restricted data access due to privacy concerns. In contrast, classification neural networks, similar to segmentation neural networks, capture essential parameters for identifying objects during training. This paper leverages this characteristic, combined with explainable artificial intelligence (XAI) techniques, to address the challenges of segmentation. By adapting classification neural networks for segmentation tasks, the proposed approach reduces dependency on manual segmentation. To demonstrate this concept, the Medical Segmentation Decathlon ‘Brain Tumours’ dataset was utilised. A ResNet classification neural network was trained, and XAI tools were applied to generate segmentation-like outputs. Our findings reveal that GuidedBackprop is among the most efficient and effective methods, producing heatmaps that closely resemble segmentation masks by accurately highlighting the entirety of the target object.
A scoping review of longitudinal studies of athlete burnout
(2025-02-14) Dišlere, Beate Evelīna; Mārtinsone, Kristīne; Koļesņikova, Jeļena; Department of Health Psychology and Paedagogy; Psychology Laboratory
INTRODUCTION: Prior research has shown that increasing training and competition loads, along with associated stressors, can negatively impact athletes' mental health and contribute to burnout. While athlete burnout can be associated with various negative sports-related consequences, such as withdrawal from sports or injuries. Although most studies on athlete burnout employ cross-sectional designs, longitudinal approaches could provide valuable insights into athlete burnout changes over time and potential causal relationships between variables and burnout. Therefore, this study aims to systematically examine longitudinal design studies to offer a comprehensive methodological, conceptual, and practical overview of athlete burnout and its associated factors. METHODS: Following PRISMA-ScR guidelines, this review explores what factors influence changes in burnout levels among athletes throughout a sports season. Therefore, studies were selected that examined athlete burnout across both genders, all age groups, and various sport types, using repeated measurements. Published articles from 2014 to 2024 were collected. Eligible studies were identified through three databases: PubMed, Scopus, and Web of Science. RESULTS: A total of 32 studies were analyzed. Quantitative mapping highlights study demographics, measurement approaches, and procedures, while qualitative mapping identifies 26 factors categorized as risk, protective, and factors influenced by burnout. The review highlights the use of tools like the Athlete Burnout Questionnaire and identifies optimal data collection intervals for tracking burnout dynamics. CONCLUSION: This scoping review offers insights into the multidimensional and nonlinear nature of athlete burnout, emphasizing its development through longitudinal studies and the importance of monitoring specific dimensions. The findings revealed various athlete burnout influencing personal and sport-environmental factors, including risk factors like perfectionistic concerns and negative social interaction, protective factors such as resilience-related skills and relatedness, and social support. The study emphasizes the importance of early detection and longitudinal monitoring to prevent burnout and mitigate its impact on athletes' mental health and performance. Further research is needed to explore additional risk and protective factors to develop effective interventions aimed at reducing the risk of burnout in athletes.
Case Study of Primitive Reflexes Impact on Swimming Skill Acquisition By Healthy Children
(Rēzeknes Tehnoloģiju akadēmija, 2020) Bogdanoviča, Irina; Lāriņš, Viesturs; Lubkina, Velta; Kaupužs, Aivars; Znotiņa, Daina; Latvian Academy of Sport Education (LASE)
Primitive reflexes is an automatic muscle reactions which are only present in the first few months, but can remain active in healthy children, thus, impacting on motor proficiency. There is little evidence how primitive reflexes influence on swimming skills acquisition by healthy children. The aim of the study is to examine how primitive reflexes influence swimming skills acquisition by healthy children. Subjects: two 7-year-old girls. Methods: Checklists by Oh et al., (2011) were used to evaluate swimming skill proficiency at swimming lesson 8 and 16. The results were represented as a percentage of the possible maximal score. The testing of the asymmetrical tonic neck reflex, the symmetrical tonic neck reflex, and the tonic labyrinthine reflex was done using Blythe’s, 5-point rating scale. The analysis was carried out using descriptive method. The first girl showed two reflexes at level 1, while the second girl demonstrated all tested reflexes at level 1, 2 and 3. The girl with less total score of reflexes (8%) achieved a better level of swimming proficiency (from 73% to 77%) than the girl with higher (25%) severity of these reflex (from 21% to 33%.). The obteined data evidence about influence of primitive reflexes on swimming skill acquisition by healthy children.
The relationship between international trade relations and regional development : a comprehensive analysis and assessment of influencing factors
(2024) Sirenko, Pavlo; Balian, Izolda; Martyniak, Iryna; Malakhova, Tetiana; Bakushevych, Ivanna
The evolution of the phenomenon of regionalization in old and new regionalism, regional trade agreements and their features (RTAs) is traced based on the provisions of regional science and trade relations, and it is shown that the emergence of numerous RTAs is one of the most significant trends in the modern development of international trade. Theoretical aspects of the influence of regional trade on regional development are considered, in particular within the growth of GDP. On the example of various regions (in particular, Asia-Pacific region, North American continent, South Africa), it is demonstrated that RTAs, as well as free trade areas (FTA) stimulate economic growth in participating countries through increased trade, economies of scale, knowledge and technology transfer. Moreover, it is concluded that the growing trend of regionalization contributes, on the one hand, to strengthening the processes of globalization, on the other hand, to the isolation of integration groupings from the world market and increasing their independence from external demand, allowing participating countries to resist emerging crises and economic shocks.
Utilising artificial intelligence in education : current trends, challenges, and future directions
(2024-01-01) Tymoshenko, Nataliia; Gordiichuk, Galyna; Davydova, Zhanna; Sirenko, Pavlo; Dorozhko, Yevhen
Introduction: the article is dedicated to studying the main capabilities and effectiveness of using AI in the modern education system and the impact of neural networks on developing analytical skills in learners. Method: the research is based on the comprehensive application of analysis, comparative methods, forecasting and data analysis, pedagogical observation, and generalisation methods. Results: the article establishes that AI began actively integrating into the education system in November 2022 with access to the ChatGPT service. It also identifies that the use of artificial intelligence in the education system at various levels is founded on the integration of three primary skills: learning (collection and analysis of information), thinking (analytics, choosing optimal action algorithms), and self-correction (improving setting algorithms to achieve more accurate results). It is established that there are two main directions for using AI to enhance the efficiency of the educational process: the application of generative AI (generating texts, plans, annotations, presentations, images) and predictive AI (automation of educational processes). The use of AI in the education system occurs in three main areas: implementing personalised learning, automating essential educational functions (checking tests, problems, equations, even evaluating creative works), and improving the process of distance education and self-education. Conclusions: it is determined that the main disadvantage of using AI in education is the reduction in the level of socialisation and critical thinking among learners. Therefore, it is crucial to balance using neural networks in the learning process and the presence of the teacher’s personality in this process.
Constructivism in European school education : A qualitative systematic review
(2025-01-10) Radičuks, Roberts; Bula-Biteniece, Inta; Gulbe, Antra; Paškevica, Beata; Rīga Stradiņš University; Latvian Academy of Sport Education (LASE)
This paper undertakes a qualitative systematic review focusing on the definition and application of the concept 'constructivism' within primary and secondary school education, covering students aged from 6 to 18 years, corresponding to ISCED (International Standard Classification of Education) stages 1, 2 and 3. In recent years, there has been increasing discourse advocating for a paradigm shift towards constructivism in educational studies. Yet, within the realm of school education, there exists considerable diversity among authors in their interpretations of constructivism, contributing to a wide range of perspectives on its practical implementation. The aim of this study is to investigate how research literature in the field of school education defines and applies constructivism, and to describe the possible factors contributing to varying interpretations of constructivism. A review of peer-reviewed scientific articles on the practical implementation of constructivism in Europe encompassed studies from 37 countries-Eurydice Network national units (27 EU Member States along with Albania, Bosnia and Herzegovina, the Republic of North Macedonia, Iceland, Liechtenstein, Montenegro, Norway, Serbia, Switzerland and Türkiye). The study utilised following databases: EBSCOhost (including Academic Search Ultimate, Academic Search Complete, Central & Eastern European Academic Source, ERIC), Google Scholar, Scopus, and Web of Science. 33 articles that met the search criteria were chosen for analysis. As a result of the review, four conceptual categories were identified and formulated: Individual domain, Social domain, Cognitive domain, and Emotional domain. Various theoretical paradigms as potential causes for the diversity of definitions are posited. The results from this study can assist educators in gaining a deeper understanding and application of the constructivism concept. The core categories identified in definitions and usage of constructivism represent an asset for school pedagogy, applicable in both theory and practice.
A Recreational Company’s Visual Identity and Its Creation
(2024) Smukā, Ingrīda; Liepiņa, Inga; Latvian Academy of Sport Education (LASE)
New recreational companies are founded every year. Recreation companies founded in Latvia are small, so great attention must be paid to creating a company’s identity. The viability of a company depends on whether the consumer will notice it and whether there will be interest in the recreational service offered by the company. Advertising is very important in today’s world, which is shaped by technology and social networks. Advertising should be short and targeted in order to attract and keep the attention of the target audience. Therefore, the following research goal was set – to study the creation of a leisure company’s visual identity (logo) and the impact of the logo on the consumer. During the research, company logos were examined, as well as document content analysis. An analysis of good practices in successful recreation companies was also conducted. During the study, recommendations from several companies and other researchers for creating a successful logo were analyzed. The study identified the elements of visual identity and also explored the significance of the company’s logotype and shape.
Reconstruction of a regulated two-cell metabolic model to study biohydrogen production in a diazotrophic cyanobacterium Anabaena variabilis ATCC 29413
(2020-01-01) Shahkouhi, Ali Malek; Motamedian, Ehsan
Anabaena variabilis is a diazotrophic filamentous cyanobacterium that differentiates to heterocysts and produces hydrogen as a byproduct. Study on metabolic interactions of the two differentiated cells provides a better understanding of its metabolism especially for improving hydrogen production. To this end, a genome-scale metabolic model for Anabaena variabilis ATCC 29413, iAM957, was reconstructed and evaluated in this research. Then, the model and transcriptomic data of the vegetative and heterocyst cells were applied to construct a regulated two-cell metabolic model. The regulated model improved prediction for biomass in high radiation levels. The regulated model predicts that heterocysts provide an oxygen-free environment and then, this model was used to find strategies for improving hydrogen production in heterocysts. The predictions indicate that the removal of uptake hydrogenase improves hydrogen production which is consistent with previous empirical research. Furthermore, the regulated model proposed activation of some reactions to provide redox cofactors which are required for improving hydrogen production up to 60% by bidirectional hydrogenase.
ACBM : An Integrated Agent and Constraint Based Modeling Framework for Simulation of Microbial Communities
(2020-12-01) Karimian, Emadoddin; Motamedian, Ehsan
The development of new methods capable of more realistic modeling of microbial communities necessitates that their results be quantitatively comparable with experimental findings. In this research, a new integrated agent and constraint based modeling framework abbreviated ACBM has been proposed that integrates agent-based and constraint-based modeling approaches. ACBM models the cell population in three-dimensional space to predict spatial and temporal dynamics and metabolic interactions. When used to simulate the batch growth of C. beijerinckii and two-species communities of F. prausnitzii and B. adolescent., ACBM improved on predictions made by two previous models. Furthermore, when transcriptomic data were integrated with a metabolic model of E. coli to consider intracellular constraints in the metabolism, ACBM accurately predicted growth rate, half-rate constant, and concentration of biomass, glucose, and acidic products over time. The results also show that the framework was able to predict the metabolism changes in the early stationary compared to the log phase. Finally, ACBM was implemented to estimate starved cells under heterogeneous feeding and it was concluded that a percentage of cells are always subject to starvation in a bioreactor with high volume.
Limiting Factors in Achieving Swimming Performance
(2024) Brat, Valentina; Teodorescu, Silvia; Aura, Bota; Kļaviņa, Aija; Rīga Stradiņš University
Aim. The paper focuses on aspects regarding performance swimming in Romania over the past decade, taking into account several variables such as the number of athletes, infrastructure, competition system, issues faced by athletes and coaches, as well as the impact of the COVID-19 pandemic. Methods. We analyzed data provided by the Romanian Swimming and Modern Pentathlon Federation (F.R.N.P.M.) and conducted surveys to better understand the current situation and challenges facing the swimming community in Romania. Results. We developed two questionnaires, one addressed to athletes consisting of 23 items and one addressed to coaches, with 17 items. A total of 75 competitive swimmers, with an average age of 15.75 years, and 31 coaches responded to the questionnaires. The results confirmed the hypothesis that in Romania, as well, the adolescent period represents the stage where the dropout rate from competitive swimming is the highest and that the COVID-19 pandemic had negative consequences on athletes' preparation and increased the number of swimmers who withdrew from competitive sports activities. Conclusions. It is essential to identify the factors that lead athletes to drop out or prematurely cease their sports activity, especially in the case of performance swimming, before they reached their peak performance. This is an initial step in developing solutions that motivate them to continue performing at the highest level, in the senior category.
A system-oriented strategy to enhance electron production of Synechocystis sp. PCC6803 in bio-photovoltaic devices : experimental and modeling insights
(2021-12) Firoozabadi, Hossein; Mardanpour, Mohammad Mahdi; Motamedian, Ehsan
Bio-photovoltaic devices (BPVs) harness photosynthetic organisms to produce bioelectricity in an eco-friendly way. However, their low energy efficiency is still a challenge. A comprehension of metabolic constraints can result in finding strategies for efficiency enhancement. This study presents a systemic approach based on metabolic modeling to design a regulatory defined medium, reducing the intracellular constraints in bioelectricity generation of Synechocystis sp. PCC6803 through the cellular metabolism alteration. The approach identified key reactions that played a critical role in improving electricity generation in Synechocystis sp. PCC6803 by comparing multiple optimal solutions of minimal and maximal NADH generation using two criteria. Regulatory compounds, which controlled the enzyme activity of the key reactions, were obtained from the BRENDA database. The selected compounds were subsequently added to the culture media, and their effect on bioelectricity generation was experimentally assessed. The power density curves for different culture media showed the BPV fed by Synechocystis sp. PCC6803 suspension in BG-11 supplemented with NH4Cl achieved the maximum power density of 148.27 mW m−2. This produced power density was more than 40.5-fold of what was obtained for the BPV fed with cyanobacterial suspension in BG-11. The effect of the activators on BPV performance was also evaluated by comparing their overpotential, maximum produced power density, and biofilm morphology under different conditions. These findings demonstrated the crucial role of cellular metabolism in improving bioelectricity generation in BPVs.
“Pretīgi bija uz Jums skatīties TV ekrānā” : agresija pret žurnālistiem portālā X (Twitter): vīriešu un sieviešu salīdzinājums
(2024-12-09) Sedlenieks, Klāvs
Pētījuma pamatjautājums ir: Vai žurnālistes piedzīvo lielāku agresiju portālā X, salīdzinājumā ar žurnālistiem vīriešiem? Pētījuma gaitā tika apkopoti ieraksti, kas adresēti septiņdesmit pieciem Latvijas žurnālistiem laika posmā no 2023. gada decembra līdz 2024. gada oktobrim: 54 950 žurnālistiem adresētu ierakstu. Tāpat tika apkopoti arī 31 042 žurnālistu pašu publicētie ieraksti. Analīzes vajadzībām tika atlasīti 49 žurnālistiem (25 sievietes, 24 vīrieši) adresēti ieraksti: kopā 18 615 ieraksti. Analīzei tika izmantots mākslīgā intelekta rīks ChatGPT 4.0, kuram tika uzdots novērtēt to, vai ieraksta autors pauž agresiju vai atbalstu pret attiecīgo žurnālistu skalā no -10 (ļoti agresīvs) līdz +10 (ļoti atbalstošs), kur neitrāls vērtējums ir 0. Iegūtie rezultāti tika apkopoti katram žurnālistam atsevišķi un vīriešu un sieviešu rezultāti tika salīdzināti dažādos griezumos. Analīzes rezultātā secināts, ka, lai gan skaitliskā izteiksmē sievietēm adresētie ieraksti liecina par nedaudz augstāku agresijas līmeni, kopējās atšķirības nav statistiski nozīmīgas.
Reconstruction of a generic genome-scale metabolic network for chicken : Investigating network connectivity and finding potential biomarkers
(2022-03) Salehabadi, Ehsan; Motamedian, Ehsan; Shojaosadati, Seyed Abbas
Chicken is the first sequenced avian that has a crucial role in human life for its meat and egg production. Because of various metabolic disorders, study the metabolism of chicken cell is important. Herein, the first genome-scale metabolic model of a chicken cell named iES1300, consists of 2427 reactions, 2569 metabolites, and 1300 genes, was reconstructed manually based on KEGG, BiGG, CHEBI, UNIPROT, REACTOME, and MetaNetX databases. Interactions of metabolic genes for growth were examined for E. coli, S. cerevisiae, human, and chicken metabolic models. The results indicated robustness to genetic manipulation for iES1300 similar to the results for human. iES1300 was integrated with transcriptomics data using algorithms and Principal Component Analysis was applied to compare context-specific models of the normal, tumor, lean and fat cell lines. It was found that the normal model has notable metabolic flexibility in the utilization of various metabolic pathways, especially in metabolic pathways of the carbohydrate metabolism, compared to the others. It was also concluded that the fat and tumor models have similar growth metabolisms and the lean chicken model has a more active lipid and carbohydrate metabolism.
Investigating role of abiotic side and finding optimum abiotic condition for improving gas biodesulfurization using Thioalkalivibrio versutus
(2022-12) Peighami, Reza; Motamedian, Ehsan; Rasekh, Behnam; Yazdian, Fatemeh
Hydrogen sulfide (H2S) is a super toxic substance that produces SOx gases when combusted. Therefore, it should be removed from gas streams. Biodesulfurization is one of the developing methods for removing sulfide. Gas biodesulfurization must be accelerated to be competitive with chemical processes. This process has two sides: biotic and abiotic sides. To increase the rate of sulfide removal, this substance should be given to the bacteria in the maximum amount (Max. − RHS B). Therefore, it is necessary to minimize the rate of adverse abiotic reactions of sulfide (Min. − RHS A). Minimizing the sulfide reaction with biosulfur and oxygen and thiosulfate generation (Min. − RHS thio2) was assessed in de-microbized medium. It was concluded that the pH should be kept as low as possible. The kinetics of thiosulfate formation from sulfide oxidation (− RHS thio1) are strongly dependent on the sulfide concentration, and to minimize this reaction rate, sulfide should be gently injected into the culture. To minimize sulfide reduction to hydrogen sulfide (Min. − RHS rev), the pH should be kept as high as possible. Using the Design Expert v.13, a model was driven for the abiotic side to obtain optimum condition. The pH value was found to be 8.2 and the sulfide concentration to 2.5E−05 M. Thioalkalivibrio versutus cultivation under identified abiotic conditions resulted in biological removal of sulfide up to 1.5 g/h. The culture was not able to remove 2 g/h input sulfide, and to increase this, the biotic side should be studied.
Metabolic regulation boosts bioelectricity generation in Zymomonas mobilis microbial fuel cell, surpassing ethanol production
(2023-12) Ahmadpanah, Hananeh; Motamedian, Ehsan; Mardanpour, Mohammad Mahdi
Zymomonas mobilis (Z. mobilis), a bacterium known for its ethanol production capabilities, can also generate electricity by transitioning from ethanol production to electron generation. The purpose of this study is to investigate the ability of Z. mobilis to produce bioelectricity when utilized as a biocatalyst in a single-chamber microbial fuel cell (MFC). Given the bacterium's strong inclination towards ethanol production, a metabolic engineering strategy was devised to identify key reactions responsible for redirecting electrons from ethanol towards electricity generation. To evaluate the electroactivity of cultured Z. mobilis and its ethanol production in the presence of regulators, the reduction of soluble Fe(III) was utilized. Among the regulators tested, CuCl2 demonstrated superior effectiveness. Consequently, the MFC was employed to analyze the electrochemical properties of Z. mobilis using both a minimal and modified medium. By modifying the bacterial medium, the maximum current and power density of the MFC fed with Z. mobilis increased by more than 5.8- and sixfold, respectively, compared to the minimal medium. These findings highlight the significant impact of metabolic redirection in enhancing the performance of MFCs. Furthermore, they establish Z. mobilis as an active electrogenesis microorganism capable of power generation in MFCs.
Investigating ethanol production using the Zymomonas mobilis crude extract
(2023-12) Aminian, Amirhossein; Motamedian, Ehsan
Cell-free systems have become valuable investigating tools for metabolic engineering research due to their easy access to metabolism without the interference of the membrane. Therefore, we applied Zymomonas mobilis cell-free system to investigate whether ethanol production is controlled by the genes of the metabolic pathway or is limited by cofactors. Initially, different glucose concentrations were added to the extract to determine the crude extract's capability to produce ethanol. Then, we investigated the genes of the metabolic pathway to find the limiting step in the ethanol production pathway. Next, to identify the bottleneck gene, a systemic approach was applied based on the integration of gene expression data on a cell-free metabolic model. ZMO1696 was determined as the bottleneck gene and an activator for its enzyme was added to the extract to experimentally assess its effect on ethanol production. Then the effect of NAD+ addition at the high concentration of glucose (1 M) was evaluated, which indicates no improvement in efficiency. Finally, the imbalance ratio of ADP/ATP was found as the controlling factor by measuring ATP levels in the extract. Furthermore, sodium gluconate as a carbon source was utilized to investigate the expansion of substrate consumption by the extract. 100% of the maximum theoretical yield was obtained at 0.01 M of sodium gluconate while it cannot be consumed by Z. mobilis. This research demonstrated the challenges and advantages of using Z. mobilis crude extract for overproduction.

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