Effect of problem-based learning tutor seniority on medical students' emotions: an equivalence study.

BACKGROUND: The effectiveness of peer learning has been recognized and discussed by many scholars, and implemented in the formal curriculums of medical schools internationally. However, there is a general dearth of studies in measuring the objective outcomes in learning. METHODS: We investigated the objective effect of near-peer learning on tutee's emotions and its equivalence within the formal curriculum of a clinical reasoning Problem Based Learning session in a Japanese medical school. Fourth-year medical students were assigned to the group tutored by 6th-year students or by faculties. The positive activating emotion, positive deactivating emotion, negative activating emotion, negative deactivating emotion, Neutral emotion were measured using the Japanese version of the Medical Emotion Scale (J-MES), and self-efficacy scores were also assessed. We calculated the mean differences of these variables between the faculty and the peer tutor groups and were statistically analyzed the equivalence of these scores. The equivalence margin was defined as a score of 0.4 for J-MES and 10.0 for the self-efficacy score, respectively. RESULTS: Of the 143 eligible participant students, 90 were allocated to the peer tutor group and 53 were allocated to the faculty group. There was no significant difference between the groups. The 95% confidence interval of the mean score difference for positive activating emotions (-0.22 to 0.15), positive deactivating emotions (-0.35 to 0.18), negative activating emotions (-0.20 to 0.22), negative deactivating emotions (-0.20 to 0.23), and self-efficacy (-6.83 to 5.04) were withing the predetermined equivalence margins for emotion scores, meaning that equivalence was confirmed for these variables. CONCLUSIONS: Emotional outcomes were equivalent between near-peer PBL sessions and faculty-led sessions. This comparative measurement of the emotional outcomes in near-peer learning contributes to understanding PBL in the field of medical education.

Enhancement of acetyl-CoA flux for photosynthetic chemical production by pyruvate dehydrogenase complex overexpression in Synechococcus elongatus PCC 7942.

Genetic manipulation in cyanobacteria enables the direct production of valuable chemicals from carbon dioxide. However, there are still very few reports of the production of highly effective photosynthetic chemicals. Several synthetic metabolic pathways (e.g., isopropanol, acetone, isoprene, and fatty acids) have been constructed by branching from acetyl-CoA and malonyl-CoA, which are key intermediates for photosynthetic chemical production downstream of pyruvate decarboxylation. Recent reports of the absolute determination of cellular metabolites in Synechococcus elongatus PCC 7942 have shown that its acetyl-CoA levels corresponded to about one hundredth of the pyruvate levels. In short, one of the reasons for lower photosynthetic chemical production from acetyl-CoA and malonyl-CoA was the smaller flux to acetyl-CoA. Pyruvate decarboxylation is a primary pathway for acetyl-CoA synthesis from pyruvate and is mainly catalyzed by the pyruvate dehydrogenase complex (PDHc). In this study, we tried to enhance the flux toward acetyl-CoA from pyruvate by overexpressing PDH genes and, thus, catalyzing the conversion of pyruvate to acetyl-CoA via NADH generation. The overexpression of PDH genes cloned from S. elongatus PCC 7942 significantly increased PDHc enzymatic activity and intracellular acetyl-CoA levels in the crude cell extract. Although growth defects were observed in overexpressing strains of PDH genes, the combinational overexpression of PDH genes with the synthetic metabolic pathway for acetate or isopropanol resulted in about 7-fold to 9-fold improvement in its production titer, respectively (9.9 mM, 594.5 mg/L acetate, 4.9 mM, 294.5 mg/L isopropanol). PDH genes overexpression would, therefore, be useful not only for the production of these model chemicals, but also for the production of other chemicals that require acetyl-CoA as a key precursor.

[Factors that affect dietitians and registered dietitians' learning about dental caries and periodontal disease].

Objectives　The present study examined factors that affect learning about dental caries and periodontal disease before or after graduation or completion of training for dietitians and registered dietitians.Methods　A questionnaire survey was conducted with members of the Aomori Prefectural Dietetic Association between October and November 2019, and 276 participants were included in the analysis. A multiple logistic regression analysis was performed to assess the characteristics associated with learning about dental caries and periodontal disease; odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated. The following independent variables were assessed: age (<30, 30-39, 40-49, 50-59, or ≥60 years), license (dietitian or registered dietitian), and occupational field (medical institution [nutrition management or food service], administrative agency, nursing care insurance facility, school-related work, training instructor in training facility for dietitians and registered dietitians, or other).Results　The multiple logistic regression analysis showed that dietitians and registered dietitians who had learned about dental caries and periodontal disease during training tended to be below the age of 40 years and have a registered dietitian license (dental caries: OR=2.79, 95% CI=1.08-7.24; periodontal disease: OR=6.51, 95% CI=1.71-24.84). Furthermore, dietitians and registered dietitians who had learned about dental caries and periodontal disease after graduation or training completion tended to be over the age of 40, have studied at a training facility (dental caries: OR=3.21, 95% CI=1.65-6.27; periodontal disease: OR=3.06, 95% CI=1.32-7.12), and be employed in the field of school-related work (dental caries: OR=4.23, 95% CI=1.03-17.27; periodontal disease: OR=5.56, 95% CI=1.15-26.98).Conclusions　To facilitate increased cooperation among practitioners in the fields of nutrition and dental health, necessary opportunities for learning about dental caries and periodontal disease alongside experts should be provided to those who do not have a registered dietitian license and have not studied at training facilities.

Synthetic microbial consortium with specific roles designated by genetic circuits for cooperative chemical production.

Synthetic microbial consortia consisting of microorganisms with different synthetic genetic circuits or divided synthetic metabolic pathway components can exert functions that are beyond the capacities of single microorganisms. However, few consortia of microorganisms with different synthetic genetic circuits have been developed. We designed and constructed a synthetic microbial consortium composed of an enzyme-producing strain and a target chemical-producing strain using Escherichia coli for chemical production with efficient saccharification. The enzyme-producing strain harbored a synthetic genetic circuit to produce beta-glucosidase, which converts cellobiose to glucose, destroys itself via the lytic genes, and release the enzyme when the desired cell density is reached. The target chemical-producing strain was programmed by a synthetic genetic circuit to express enzymes in the synthetic metabolic pathway for isopropanol production when the enzyme-producing strain grows until release of the enzyme. Our results demonstrate the benefits of synthetic microbial consortia with distributed tasks for effective chemical production from biomass.

Reconstruction of a metabolic regulatory network in Escherichia coli for purposeful switching from cell growth mode to production mode in direct GABA fermentation from glucose.

γ-aminobutyric acid (GABA) is a drug and functional food additive and is used as a monomer for producing the biodegradable plastic, polyamide 4. Recently, direct GABA fermentation from glucose has been developed as an alternative to glutamate-based whole cell bioconversion. Although total productivity in fermentation is determined by the specific productivity and cell amount responsible for GABA production, the optimal metabolic state for GABA production conflicts with that for bacterial cell growth. Herein, we demonstrated metabolic state switching from the cell growth mode based on the metabolic pathways of the wild type strain to a GABA production mode based on a synthetic metabolic pathway in Escherichia coli through rewriting of the metabolic regulatory network and pathway engineering. The GABA production mode was achieved by multiple strategies such as conditional interruption of the TCA and glyoxylate cycles, engineering of GABA production pathway including a bypass for precursor metabolite supply, and upregulation of GABA transporter. As a result, we achieved 3-fold improvement in total GABA production titer and yield (4.8g/L, 49.2% (mol/mol glucose)) in batch fermentation compared to the case without metabolic state switching (1.6g/L, 16.4% (mol/mol glucose)). This study reports the highest GABA production performance among previous reports on GABA fermentation from glucose using engineered E. coli.

Change in hand dexterity and habitual gait speed reflects cognitive decline over time in healthy older adults: a longitudinal study.

[Purpose] There is a relationship between physical and cognitive functions; therefore, impairment of physical function would mean cognitive decline. This study aimed to investigate the association between change in physical and cognitive functions. [Subjects and Methods] Participants were 169 healthy community-dwelling older adults who attend the survey after three years from baseline (mean age, 72.4 ± 4.8 years). Grip strength, one-leg standing balance, five-times-sit-to-stand test, timed up and go, 5-m habitual walk, and a peg-moving task were used to evaluate physical performance. Five cognitive function tests were used to assess attention, memory, visuospatial function, verbal fluency, and reasoning. Cognitive function was defined as the cumulative score of these tests. [Results] At baseline, five-times-sit-to-stand test, timed up and go, and hand dexterity were independently associated with cognitive function. In longitudinal analyses, changes in habitual walking speed and hand dexterity were significantly associated with change in cognitive function. [Conclusion] Deterioration of specific physical function, such as hand dexterity and walking ability, may be associated with progression of cognitive decline. Decreasing extent of daily functions, such as hand dexterity and walking ability, can be useful indices to grasp changes in cognitive function.

Self-induced metabolic state switching by a tunable cell density sensor for microbial isopropanol production.

Chemicals production by engineered microorganisms often requires induction of target gene expression at an appropriate cell density to reduce conflict with cell growth. The lux system in Vibrio fischeri is a well-characterized model for cell density-dependent regulation of gene expression termed quorum sensing (QS). However, there are currently no reports for application of the lux system to microbial chemical production. Here, we constructed a synthetic lux system as a tunable cell density sensor-regulator using a synthetic lux promoter and a positive feedback loop in Escherichia coli. In this system, self-induction of a target gene expression is driven by QS-signal, and its threshold cell density can be changed depending on the concentration of a chemical inducer. We demonstrate auto-redirection of metabolic flux from central metabolic pathways toward a synthetic isopropanol pathway at a desired cell density resulting in a significant increase in isopropanol production.

[Factors regarding awareness of preventive care exercises: Distance to exercise facilities and their social networks].

OBJECTIVES: The present study examines factors affecting individuals' awareness of certain types of preventive care exercises, particularly the distance from their home to an exercise facility and their social networks. METHODS: Participants were 3206 men (age, 73.0±6.2 years) and 3395 women (age, 73.2±6.4 years) aged ≥65 years who had not been certified as persons with care needs and who had responded to an inventory survey conducted in Kasama City, Japan, in 2013. We performed multiple logistic regression analysis to assess the characteristics associated with participants' awareness of two types of exercises for preventive care: "silver rehabili taisou" (SRT) and "square-stepping exercise" (SSE). Independent variables were distance from home to the exercise facility, social networks, transportation availability, physical function, cognitive function, and neighborhood population density. RESULTS: Older adults who were aware of the exercises lived significantly closer to an exercise facility (SRT, aware: 1,148.5±961.3 m vs. unaware: 1,284.2±1,027.4 m; SSE, aware: 1,415.9±1104.1 m vs. unaware: 1,615.7±1,172.2 m). Multiple logistic regression analysis showed that participation in community activities (men, SRT-odds ratio [OR]=2.54 and SSE-OR=2.19; women, SRT-OR=4.14 and SSE-OR=3.34] and visiting friends (men, SRT-OR=1.45 and SSE-OR=1.49; women SRT-OR=1.44 and SSE-OR=1.73) were promoting factors for awareness of both types of exercises. In men and women, low physical function (SRT-OR=0.73 and SSE-OR=0.56) and dependence on another person to drive them to the destination (SRT-OR=0.79 and SSE-OR=0.78) were inhibiting factors, respectively. A distance of >500 m between their home and the facility tended to be an inhibiting factor. CONCLUSION: A shorter distance from home to an exercise facility and better social networks increased awareness of preventive care exercises in both sexes and for both types of exercise. Establishing exercise centers and devising effective methods of imparting information to individuals (e.g., via community magazines and home visits) may promote participation in preventive care exercises.

[Validity and reliability of the "Trail Making Peg" test as a performance measurement for evaluating the cognitive function].

AIM: To investigate the validity and reliability of a novel performance test, called the "Trail Making Peg" (TMP) test, for evaluating the cognitive function. METHODS: We recruited 632 community-dwelling older adults (mean age: 73.3±5.2 years) as subjects for the assessment of the validity of the test and 319 adults (mean age: 73.1±5.2 years) as subjects for the assessment of reliability. Five cognitive tests (5-Cog) were used to evaluate the cognitive function, and the degree of cognitive decline was delineated for subjects scoring below 1 SD from the mean 5-Cog score. A receiver operating characteristic analysis was employed to calculate the cut-off point. RESULTS: There were no sex differences in the TMP scores (P=0.951), and the TMP and 5-Cog scores were found to correlate significantly (r=-0.63) with each other. The Trail Making Peg test demonstrated an area under the curve of 0.855 for discriminating between non-cognitive decline and cognitive decline. At this cutoff point, the sensitivity was 85% and the specificity was 69%. The intraclass correlation coefficient of the TMP was 0.746. CONCLUSIONS: The TMP exhibits sufficient validity and reliability. Our results suggest that TMP is a useful screening test for detecting cognitive decline.

Metabolic flux redirection from a central metabolic pathway toward a synthetic pathway using a metabolic toggle switch.

Overexpression of genes in production pathways and permanent knockout of genes in competing pathways are often employed to improve production titer and yield in metabolic engineering. However, the deletion of a pathway responsible for growth and cell maintenance has not previously been employed, even if its competition with the production pathway is obvious. In order to optimize intracellular metabolism at each fermentation phase for bacterial growth and production, a methodology employing conditional knockout is required. We constructed a metabolic toggle switch in Escherichia coli as a novel conditional knockout approach and applied it to isopropanol production. The resulting redirection of excess carbon flux caused by interruption of the TCA cycle via switching gltA OFF improved isopropanol production titer and yield up to 3.7 and 3.1 times, respectively. This approach is a useful tool to redirect carbon flux responsible for bacterial growth and/or cell maintenance toward a synthetic production pathway.

[Determinants of changes in physical fitness after a square-stepping exercise program in community-dwelling older Japanese females].

AIM: The purpose of this study was to investigate determinants of changes in physical fitness after a fall-prevention exercise program in older females. METHODS: The study subjects included 83 community-dwelling females 65 years of age or older (mean age: 70.4±4.0 years) living in Kasama City, rural Japan. All subjects participated in a fall-prevention exercise program called square-stepping exercise (SSE) conducted once a week for 11 weeks. In order to assess the physical fitness benefits of by the exercise program, we measured the results of five physical performance tests: grip strength, one leg stand, sit and reach, timed up and go and the choice-stepping reaction time. In addition, we evaluated comprehensive physical fitness scores based on the standardized total score of the five physical performance tests. The changes in the comprehensive physical fitness score between baseline and after the program was used as the dependent variable, while the baseline values of age, education, clinical history, physical activity, Lubben social network scale, geriatric depression scale, five cognitive function test result, comprehensive physical fitness score and percentage of attendance were treated as independent variables. RESULTS: A stepwise multiple regression analysis revealed that the change in comprehensive physical fitness score correlated significantly with the baseline values of age (ß=-0.273), the five cognitive function test result (ß=0.293) and comprehensive physical fitness score (ß=-0.607). CONCLUSIONS: These results suggest that older females with a low level of physical fitness at baseline are more likely to improve their physical fitness with a period of exercise training. However, the improvements in physical fitness are lower in older females with a low level of cognitive function than in those with a high level of cognitive function.

Adapting the Motivated Strategies for Learning Questionnaire to the Japanese Problem-Based Learning Context: A Validation Study.

The COVID-19 pandemic has greatly changed medical education, and medical trainees' self-regulation has become more emphasized. In Japan, the concept of self-regulated learning has not been fully applied in health profession education due to a lack of effective measurement tools. We aimed to validate the translated Japanese version of the Motivated Strategies for Learning Questionnaire in the context of Problem-Based Learning (J-MSLQ-PBL). The questionnaire employs a seven-point Likert-type scale with 81 items and is categorized into two sections: motivation and learning strategies. An exploratory factor analysis (EFA) was conducted by using Promax rotation to examine the factor structure of the scale, using the collected data from 112 Japanese medical students. Factor extraction was based on a scree plot investigation, and an item was accepted when the factor loading was ≥0.40. In the motivation section, the extracted factors from the EFA were well aligned with the subscales of the original MSLQ, including "Self-Efficacy for Learning and Performance", "Task Value", "Self-Efficacy for Learning and Performance", "Test Anxiety", "Extrinsic Goal Orientation", and "Intrinsic Goal Orientation". In the learning strategies, the extracted factors poorly matched the structure of the original subscales. This discrepancy could be explained by insufficient translation, the limited sample size from a single medical school, or cross-cultural differences in learning strategies between Western and Japanese medical students. Only the motivation part of the J-MSLQ-PBL should be implemented to measure the competency elements of self-regulated learning in Japan.

A hybrid in silico/in-cell controller for microbial bioprocesses with process-model mismatch.

Bioprocess optimization using mathematical models is prevalent, yet the discrepancy between model predictions and actual processes, known as process-model mismatch (PMM), remains a significant challenge. This study proposes a novel hybrid control system called the hybrid in silico/in-cell controller (HISICC) to address PMM by combining model-based optimization (in silico feedforward controller) with feedback controllers utilizing synthetic genetic circuits integrated into cells (in-cell feedback controller). We demonstrated the efficacy of HISICC using two engineered Escherichia coli strains, TA1415 and TA2445, previously developed for isopropanol (IPA) production. TA1415 contains a metabolic toggle switch (MTS) to manage the competition between cell growth and IPA production for intracellular acetyl-CoA by responding to external input of isopropyl ß-D-1-thiogalactopyranoside (IPTG). TA2445, in addition to the MTS, has a genetic circuit that detects cell density to autonomously activate MTS. The combination of TA2445 with an in silico controller exemplifies HISICC implementation. We constructed mathematical models to optimize IPTG input values for both strains based on the two-compartment model and validated these models using experimental data of the IPA production process. Using these models, we evaluated the robustness of HISICC against PMM by comparing IPA yields with two strains in simulations assuming various magnitudes of PMM in cell growth rates. The results indicate that the in-cell feedback controller in TA2445 effectively compensates for PMM by modifying MTS activation timing. In conclusion, the HISICC system presents a promising solution to the PMM problem in bioprocess engineering, paving the way for more efficient and reliable optimization of microbial bioprocesses.

Acceptable walking and cycling distances and functional disability and mortality in older Japanese adults: An 8-year follow-up study.

We prospectively investigated the association between acceptable travel distances (i.e., walking and cycling) and the incidence of functional disability and mortality among older Japanese adults. A baseline survey was conducted in 2013 among 7618 individuals aged ≥65 years in Kasama City, Japan, and they were tracked through the city's database until 2021. Acceptable travel distances were assessed using a questionnaire. Outcomes (i.e., functional disability and mortality) were gathered as binary (incident or not) with survival time. A multivariable-adjusted Cox proportional-hazards model indicated that shorter acceptable walking and cycling distances were markedly linked with higher risks of functional disability and mortality. In conclusion, acceptable distances of ≤500 m for walking and ≤1 km for cycling were associated with higher risks of functional disability and mortality among older adults.

Trace impurities in sodium phosphate influences the physiological activity of Escherichia coli in M9 minimal medium.

In the field of applied microbiology, reproducibility and experimental variability are important factors that influence both basic research as well as process development for industrial applications. Experimental reproducibility and accuracy depend not only on culture conditions such as temperature and aeration but also on raw materials and procedures used for media preparation. The M9 minimal medium is one of the most common synthetic media for culturing Escherichia coli and other bacteria. This synthetic medium can be used to observe and evaluate the physiological activity of microbes under minimal nutritional requirements and determine the limiting factor for the desired phenotype. Although one of the advantages using the M9 medium is that its composition can be modulated, it is difficult to control presence of trace components and impurities from the reagents for preparing this medium. Herein, we showed that trace ingredients present in the reagents used for M9 media preparation affect the bacterial physiological activities (e.g., cell growth, substrate consumption, and byproduct formation). Additionally, we systematically identified the trace ingredient that influenced phenotypic differences. Our results showed that the selection of reagents and accuracy during reagent preparation is important for experimental reproducibility in the field of bio-engineering and systems biology focused on the systematic and continuous development of biomolecular systems (e.g., biorefinery, metabolic engineering, and synthetic biology).

Complex motivations of Japanese medical students to an online medical English course during the COVID-19 pandemic.

Background: In response to globalism, many East-Asian countries now include a Medical English course in their undergraduate medical education syllabus. The purpose of this study was to explore the relationship between the related attribute factors of students' motivation to learn medical English through an online modality. Methods: Of 134 eligible fourth-year medical students who participated in an Online Medical English course at a Japanese medical school, 105 were enrolled in this single cohort study. The participants completed pre- and post-course surveys regarding their motivation during the course, including perceived academic control and task value, and their assignment scores. A structural equation model was used to examine the hypothesized relationship of constructs, based on control-value theory. Results: The model showed a good fit for the data (χ 2[df=7] = 1.821, p=0.969, CFI = 1.000, RMSEA < 0.001, SRMR < 0.05, GFI = 0.993, AGFI = 0.980). The latent variables of the perceived course achievement related to the observed variables of academic control and task value scale scores, and negatively predicted willingness for self-study after course completion. In addition, the preference of English as the course language negatively predicted willingness for self-study of medical English. Conclusion: Choice of English as the language of instruction and perceived high course achievement negatively predicted students' motivation for further English self-study after the class. The importance of incorporating the perspective of lifelong learning into the teaching of medical English was recognized.

Dynamic metabolic engineering of Escherichia coli improves fermentation for the production of pyruvate and its derivatives.

Pyruvate is a key intermediate that is involved in various synthetic metabolic pathways for microbial chemical and fuel production. It is widely used in the food, chemical, and pharmaceutical industries. However, the microbial production of pyruvate and its derivatives compete with microbial cell growth, as pyruvate is an important metabolic intermediate that serves as a hub for various endogenous metabolic pathways, including gluconeogenesis, amino acid synthesis, TCA cycle, and fatty acid biosynthesis. To achieve a more efficient bioprocess for the production of pyruvate and its derivatives, it is necessary to reduce the metabolic imbalance between cell growth and target chemical production. For this purpose, we devised a dynamic metabolic engineering strategy within an Escherichia coli model, in which a metabolic toggle switch (MTS) was employed to redirect metabolic flux from the endogenous pathway toward the target synthetic pathway. Through a combination of TCA cycle interruption through MTS and reduction of pyruvate consumption in endogenous pathways, we achieved a drastic improvement (163 mM, 26-fold) in pyruvate production. In addition, we demonstrated the redirection of metabolic flux from excess pyruvate toward isobutanol production. The final isobutanol production titer of the strain harboring MTS was 26% improved compared with that of the control strain.

Quantitative metabolomics for dynamic metabolic engineering using stable isotope labeled internal standards mixture (SILIS).

The production of chemicals and fuels from renewable resources using engineered microbes is an attractive alternative for current fossil-dependent industries. Metabolic engineering has contributed to pathway engineering for the production of chemicals and fuels by various microorganisms. Recently, dynamic metabolic engineering harnessing synthetic biological tools has become a next-generation strategy in this field. The dynamic regulation of metabolic flux during fermentation optimizes metabolic states according to each fermentation stage such as cell growth phase and compound production phase. However, it is necessary to repeat the evaluation and redesign of the dynamic regulation system to achieve the practical use of engineered microbes. In this study, we performed quantitative metabolome analysis to investigate the effects of dynamic metabolic flux regulation on engineered Escherichia coli for γ-amino butyrate (GABA) fermentation. We prepared a stable isotope-labeled internal standard mixture (SILIS) for the stable isotope dilution method (SIDM), a mass spectrometry-based quantitative metabolome analysis method. We found multiple candidate bottlenecks for GABA production. Some metabolic reactions in the GABA production pathway should be engineered for further improvement in the direct GABA fermentation with dynamic metabolic engineering strategy.

In-Needle Pre-Column Derivatization for Amino Acid Quantification (iPDAQ) Using HPLC.

Pre-column fluorescent derivatization has been used for the fast quantification of amino acids using high-performance liquid chromatography (HPLC) systems. However, it generally requires an offline in-vial derivatization process with multiple derivatization reagents. The offline derivatization requires the same number of reaction vials as the number of sample vials for use as a reaction chamber for the derivatization reaction in an autosampler. Therefore, the number of samples analyzed per batch using the pre-column derivatization method is halved. To benefit from the pre-column derivatization method, we transformed the derivatization process from an offline chamber process to an online in-needle process (in-needle Pre-column Derivatization for Amino acids Quantification; iPDAQ). Fluorescent derivatization in the injection needle obviated the need for vacant vials as reaction chambers. Consequently, the throughput per batch improved up to two times, and the consumption of derivatization reagents was reduced to less than one-tenth of that in the conventional vial method. We demonstrated to separate and quantify the amino acids in various biological samples. Herein, we presented a novel HPLC-based amino acid quantification method that enables the continuous analysis of a large number of samples. The iPDAQ facilitates accurate amino acid quantification due to the automation of derivatization and achieves improvement in the throughput and reduction of analysis labor.

Design of Synthetic Quorum Sensing Achieving Induction Timing-Independent Signal Stabilization for Dynamic Metabolic Engineering of E. coli.

Dynamic metabolic engineering that harnesses synthetic biological tools is a next-generation strategy for microbial chemical and fuel production. We previously reported a synthetic quorum sensing system combined with a metabolic toggle switch (QS-MTS) in E. coli. It autonomously redirected endogenous metabolic flux toward the synthetic metabolic pathway and improved biofuel production. However, its functions and effects on host metabolism were attenuated by induction timing delay. Here, we redesigned the QS-MTS to stabilize QS signaling efficiency and metabolic regulation. We performed a metabolome analysis to clarify the effects of QS-MTS redesign on host metabolism. We compared the contributions of conventional and redesigned QS-MTS to fed-batch fermentation. The redesigned QS-MTS was more conducive than the conventional QS-MTS to long-term processes such as fed-batch fermentation. Here, we present a circuit redesign for metabolic flux control based on dynamic characteristic evaluation and metabolome analysis.