Dynamic modeling and parameter estimation of biomethane production from microalgae co-digestion.

This work proposes a dynamic modeling procedure applied to biomethane production from microalgae residual co-digestion. A two-stage anaerobic digestion representation is selected, considering acidogenesis and methanogenesis as main reaction pathways. Based on the experimental database generated in the University of Mons Laboratories, several candidate models, assuming the presence or absence of biomass dynamics, are suggested, and parametric structural and local identifiability studies are performed. An original parameter estimation procedure is applied to a data-set partition used for model direct validation. The remaining experiment data are dedicated to cross-validation. The results point out how these dynamic models may serve as advanced monitoring software tools such as digital twins, even in the presence of incomplete process data.

Effectiveness and persistence of Vedolizumab in patients with inflammatory bowel disease : results from the Belgian REal-LIfe study with VEdolizumab (Be-RELIVE).

BACKGROUND AND STUDY AIMS: Vedolizumab (VDZ) is a gutselective integrin inhibitor used to treat Crohn's disease (CD) and ulcerative colitis (UC). This retrospective study assessed effectiveness and treatment persistence of VDZ in a Belgian reallife cohort of CD and UC patients. PATIENTS AND METHODS: CD and UC patients from 15 Belgian centers, who started VDZ between 01/09/2015 and 31/06/2016 and attended ≥1 visit after the first VDZ infusion, were included. Data were collected before first infusion, at week (W)10, W14 (CD patients only), month (M)6 and last follow-up. Treatment response and remission rates (changes in disease activity scores) and treatment persistence (Kaplan-Meier analysis) were assessed. RESULTS: Of the 348 patients receiving at least one dose of VDZ, 325 (202 CD, 45 biologic-naïve; and 123 UC, 42 biologic-naïve) patients were included in data analyses. At M6, 87.6% (176/201) of CD and 86.1% (105/122) of UC patients were still on VDZ treatment, 75.6% (34/45) and 83.9% (26/31) achieved clinical response, and 66.7% (44/66) and 42.9% (15/35) were in remission. At M6 remission rates was significantly higher while response rates tended to be higher among biologic-naïve versus biologic-failure CD patients. CONCLUSIONS: VDZ offers an effective treatment option in real-life settings and treatment effectiveness appears higher in biologic-naïve versus biologic-failure CD patients. (Acta gastroenterol. belg., 2020, 83, 15-23).

Sensitivity analysis and reduction of a dynamic model of a bioproduction of fructo-oligosaccharides.

Starting from a relatively detailed model of a bioprocess producing fructo-oligosaccharides, a set of experimental data collected in batch and fed-batch experiments is exploited to estimate the unknown model parameters. The original model includes the growth of the fungus Aureobasidium pullulans which produces the enzymes responsible for the hydrolysis and transfructosylation reactions, and as such contains 25 kinetic parameters and 16 pseudo-stoichiometric coefficients, which are not uniquely identifiable with the data at hand. The aim of this study is, therefore, to show how sensitivity analysis and quantitative indicators based on the Fisher information matrix can be used to reduce the detailed model to a practically identifiable model. Parametric sensitivity analysis can indeed be used to progressively simplify the model to a representation involving 15 kinetic parameters and 8 pseudo-stoichiometric coefficients. The reduced model provides satisfactory prediction and can be convincingly cross validated.

Strategies for the production of high-content fructo-oligosaccharides through the removal of small saccharides by co-culture or successive fermentation with yeast.

Fructo-oligosaccharides (FOS) obtained by fermentation of sucrose may be purified at large-scale by continuous chromatography (Simulated Moving Bed: SMB). In order to improve the efficiency of the subsequent SMB purification, the optimization of the fermentative broth composition in salts and sugars was investigated. Fermentations conducted at reduced amount of salts, using Aureobasidium pullulans whole cells, yielded 0.63 ± 0.03 g of FOS per gram of initial sucrose. Additionally, a microbial treatment was proposed to reduce the amount of small saccharides in the mixture. Two approaches were evaluated, namely a co-culture of A. pullulans with Saccharomyces cerevisiae; and a two-step fermentation in which FOS were first synthesized by A. pullulans and then the small saccharides were metabolized by S. cerevisiae. Assays were performed in 100mL shaken flasks and further scaled-up to a 3 L working volume bioreactor. Fermentations in two-step were found to be more efficient than the co-culture ones. FOS were obtained with a purity of 81.6 ± 0.8% (w/w), on a dry weight basis, after the second-step fermentation with S. cerevisiae. The sucrose amount was reduced from 13.5 to 5.4% in total sugars, which suggests that FOS from this culture broth will be more efficiently separated by SMB.

Selection of human immunodeficiency virus type 1 resistance against the pyranodipyrimidine V-165 points to a multimodal mechanism of action.

OBJECTIVES: We have previously identified the pyranodipyrimidines (PDPs) as a new class of integrase (IN) inhibitors. The most potent congener V-165 inhibits HIV-1 integration at low micromolar concentrations by inhibiting the binding of IN to the DNA. As part of pre-clinical studies with PDP, we wanted to investigate HIV resistance development against V-165 and to further characterize the physicochemical properties of the compound. METHODS: We selected PDP-resistant HIV-1 strains by growing the virus in the presence of increasing concentrations of V-165. The selected strains were analysed genotypically and phenotypically. Mutant IN enzymes were generated and evaluated in an enzymatic oligonucleotide-based assay for their activity and sensitivity to the different IN inhibitors. In addition, the antiviral effect of the compound on viral entry and integration was measured using quantitative PCR. RESULTS: Numerous mutations were detected in the RT, IN and env genes of the virus selected in the presence of V-165. Although V-165 inhibited integration in vivo as indicated by a decrease in the number of integrated proviruses, the compound also inhibited viral entry at a concentration of 19 microM. V-165 was poorly recovered from human hepatic microsomal matrix and 1% BSA. CONCLUSIONS: These data point to a multimodal mechanism of action. A quest for derivatives of V-165 that specifically target IN should be pursued.

Novel inhibitors of HIV-1 integration.

Human immunodeficiency virus (HIV) is the etiological agent of the acquired immune deficiency syndrome (AIDS). The current strategy for the treatment of HIV infection is called Highly Active Antiretroviral Therapy (HAART) and is based on cocktails of drugs that are currently approved by the Food and Drug Administration. These drugs include compounds that target the viral entry step and the enzymes reverse transcriptase or protease. The introduction of HAART has dramatically changed the landscape of HIV disease. Death from AIDS-related diseases has been reduced significantly since HAART came into use. Nevertheless it is not clear how long clinical benefit will last taking into account the emergence of multiple drug-resistant viral strains. Addition of new anti-HIV drugs targeting other steps of the viral replication cycle may increase the potency of inhibition and delay resistance development. HIV integrase is an essential enzyme in the HIV life cycle and is an attractive target for new drug development. Despite years of intensive research, only two classes of compounds that inhibit integration have been identified until now, namely the diketo acids and the pyranodipyrimidines. In this review we will point to new potential antiviral targets related to retroviral integration that are amenable to drug development. We will describe the pitfalls of currently used integrase assays and propose new strategies and technologies for the discovery of HIV integration inhibitors. Furthermore, we will describe the two classes of integrase inhibitors and discuss their antiviral activity, molecular mechanism of anti-HIV action and the selection of HIV resistance against these drugs.

Simultaneous determination of endogenous and 13C-labelled thyroid hormones in plasma by stable isotope dilution mass spectrometry.

This study describes a capillary gas chromatography-mass spectrometry (GC-MS) method for the simultaneous determination of endogenous thyroid hormone (thyroxine, T4) and its 13C-labelled analogue (13C6-thyroxine) in plasma. 13C9-thyroxine was used as analytical internal standard. A double derivatization (CH3OH/HCl and HFBA) inducing good GC mobility was used for the GC-MS analysis of the thyroid hormones. Quantification was carried out by selected ion monitoring (SIM) of specific ions of the fragment ions (m/z 970/976/979). The detection limit of the present GC-MS-SIM method was found to be 100 pg per injection for thyroxine (S/N=3.0). A first implementation in in vivo tests of 13C6-T4 like metabolic tracer was carried out under veterinary control on one cat and one rabbit. The thyroxine follow-up was done by GC-MS and based on double isotopic dilution with two different regio-selective 13C-labelled molecules of the same hormone. The present paper discusses the possibilities and limitations of this methodology. The in vivo experiment demonstrated that the use of stable isotopes and mass spectrometry provide a reliable methodology for hormonal monitoring.