Développement et application de la microfluidique digitale au criblage et à l analyse de microorganismes industriels

Ce travail de doctorat a permis d explorer l intérêt de la microfluidique digitale pour le criblage de microorganismes industriels. La première partie de ce manuscrit présente le développement de substrats fluorogéniques de glycosidases adaptés aux émulsions perfluorées utilisées en microfluidique digitale. Ces substrats ont été dans un premier temps synthétisés chimiquement puis validés par des dosages enzymatiques en microplaque, mais également sur des souches modèles en microfluidique digitale. La deuxième partie de ce manuscrit illustre l intérêt des substrats fluorogéniques susmentionnés pour cribler des bactéries cellulolytiques à partir d un échantillon de sol (chaume de blé). Enfin la dernière partie de ce manuscrit décrit le développement et la mise en œuvre de microsystèmes adaptés à l analyse et au criblage microfluidique de champignons filamenteux. Ce travail débouche aujourd hui sur la perspective de trier et sélectionner des microorganismes d intérêt à partir d échantillons issus de biotopes naturels ou encore de banques de mutants. Ces outils permettront d accélérer la découverte de nouvelles souches ou enzymes ainsi que leur amélioration par évolution dirigée.This doctoral work explored the interest of digital microfluidics for the screening of industrial microorganisms. The first part of this thesis presents the development of fluorogenic substrates of glycosidases adapted to perfluorinated emulsions used in digital microfluidics. These substrates were initially chemically synthesized and then validated by enzymatic assays microplate, but also in digital microfluidics model strains. The second part of this thesis illustrates the importance of the aforementioned fluorogenic substrates for screening cellulolytic bacteria from a soil sample (wheat straw). The last part of this thesis describes the development and implementation of microsystems suitable for analysis and microfluidic screening of filamentous fungi. This work opens today the possibility of sorting and selecting microorganisms of interest from samples collected from natural habitats or banks mutants. These tools will accelerate the discovery of new strains or enzymes and their improvement by directed evolution.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Design characteristics of corrugated trapezoidal plate heat exchangers using nanofluids

In this paper, fully developed turbulent flow and heat transfer behavior in trapezoidal channels using nanofluids are numerically studied. This study evaluates the effects of four different types of nanoparticles, Al2O3, CuO, SiO2 and ZnO, with different volume fractions (0-4%) and diameters (20-80nm) under constant heat flux (6kW/m2). The effects of geometrical parameters (wavy amplitudes, longitudinal pitch) of the trapezoidal channel on the thermal and flow fields are also examined. The results indicated that SiO2 has the highest Nusselt number among the nanofluids. Enhancement of heat transfer increases with particle volume concentration, but a slight increase in pressure loss with decreasing nanoparticle diameter is also observed. When nanofluids are used in a forced convection, 10% increase in average Nusselt number is observed for nanoparticles with a diameter of 20nm and at 4vol.%. Analysis of the flow and heat transfer in a corrugated trapezoidal channel is made based on the comprehensive evaluation factor J/f. The optimum (J/f) enhancement shows that the CuO nanofluid, lower concentration ratio of nanoparticles, trapezoidal height of 2.5mm and a longitudinal pitch of 6mm are the most desirable parameters for saving energy. Using nanofluids with a corrugated channel can improve the thermal performance because it can lead to more compact heat exchangers

Sequencing batch reactor for treatment of palm oil mill effluent

Oil palm is commonly used in commercial agricultural activities as the second leading export in Malaysia. The main by-products and wastes that are produced from oil palm includes empty fruit bunch (EFB) and palm oil mill effluent (POME) generated from sterilizer condensate, palm fibre and palm kernels. Due to its high biochemical oxygen demand (BOD) and chemical oxygen demand (COD) concentrations, POME has been recognized to be one of the main sources for environmental pollution. In this study, sequencing batch reactors (SBRs) namely experimental reactor R1 and control reactor R2 have been used at height to diameter (H/D) ratio of 17 for optimal granulation process. R1 and R2 were operated on a sequential cyclic processes comprehended of anoxic fill, react, settle, decant and idle period while simultaneously removing COD, BOD and color at organic loading rate (OLR) of 2.5 kgCOD m-3d-1. Good COD removal of up to 85% was achieved in R1 as compared to 70% in R2 indicating efficient COD removal in SBR when operated with seeding sludge. However, color removal for R2 was higher than R1 at 85% as compared to 72% which was presumably due to contributions of phenolic content in the influent

New Glycosidase Substrates for Droplet-Based Microfluidic Screening

Droplet-based microfluidics is a powerful technique allowing ultra-high-throughput screening of large libraries of enzymes or microorganisms for the selection of the most efficient variants. Most applications in droplet microfluidic screening systems use fluorogenic substrates to measure enzymatic activities with fluorescence readout. It is important, however, that there is little or no fluorophore exchange between droplets, a condition not met with most commonly employed substrates. Here we report the synthesis of fluorogenic substrates for glycosidases based on a sulfonated 7-hydroxycoumarin scaffold. We found that the presence of the sulfonate group effectively prevents leakage of the coumarin from droplets, no exchange of the sulfonated coumarins being detected over 24 h at 30 °C. The fluorescence properties of these substrates were characterized over a wide pH range, and their specificity was studied on a panel of relevant glycosidases (cellulases and xylanases) in microtiter plates. Finally, the β-d-cellobioside-6,8-difluoro-7-hydroxycoumarin-4-methanesulfonate substrate was used to assay cellobiohydrolase activity on model bacterial strains (<i>Escherichia coli</i> and <i>Bacillus subtilis</i>) in a droplet-based microfluidic format. These new substrates can be used to assay glycosidase activities in a wide pH range (4–11) and with incubation times of up to 24 h in droplet-based microfluidic systems

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licenseBackground: Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide. Methods: A multimethods analysis was performed as part of the GlobalSurg 3 study—a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital. Findings: Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3·85 [95% CI 2·58–5·75]; p<0·0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63·0% vs 82·7%; OR 0·35 [0·23–0·53]; p<0·0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer. Interpretation: Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised. Funding: National Institute for Health and Care Research