Tools for analysis and evaluation of biocatalytic processes

Recently interest in biocatalysis, the use of enzymes as catalysts, has been growing. This is due in part to the ability to achieve new and interesting chemistry, but also more sustainable, milder, aqueous processes producing less waste. With these advantages though, come new process bottlenecks. Many methods of overcoming such disadvantages have been proposed. However, key to the designer is the ability to discriminate between them at an early stage. To date several methods of early identification of bioprocess bottlenecks have been presented, though none of these has enabled the easy identification of the biocatalyst requirement in the reactor with regard to integrating upstream and downstream requirements. To this end a tool by which biocatalytic processes can be analysed and evaluated, based in part on regime analysis has been presented. The method identifies biocatalyst concentrations at which limitations that control chosen process metrics become dominating. The tool has been demonstrated by the use of a model system, the biocatalytic production of S,S- ethylenediamine-N.N'-disuccinic acid by two enzymes, EDMSase and EDDSase. The reaction is characterised by fumarate inhibition, an exotherm, competition for fumarate not least by the two half reactions, equilibria close to unity and currently an unproductive wild type fermentation. Key bottlenecks were determined to be a severe limitation by the enzyme catalysing the first step, a fumarase limitation and an equilibrium limitation. Proposal of metric hurdles enabled analysis of the dominating regimes and led to determination of the feasible operating region at 232 g.l"1 fumarate, 30 g.P1 ethylenediamine, 900 g<fcw.r1 EDDSase and 300 g.I"1 EDMSase, enzyme concentrations unachievable by current methods. Possible processes and research to overcome these limitations were proposed and analysed for their effect on the metrics indicating that in the absence of fumarase, use of in-situ product removal would improve process yield 2-fold and product concentration 3-fold

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Process limitations in a whole-cell catalysed oxidation: Sensitivity analysis

Biocatalytic oxidation processes have to date presented major problems for scale-up, in part due to the complexity of the number of process variables. In this paper we have analysed the key limitations in such processes using the Baeyer-Villiger monooxygenase catalysed synthesis of optically pure lactones as an illustrative example. Limitations in product concentration, catalyst longevity and reaction rate were quantified and their effect on previously defined process metrics identified. Of particular interest is the way these metrics change with catalyst concentration. Using this assessment, the sensitivity of the metrics to potential changes to process and catalyst were analysed. We believe such an analysis is of general use to guide development efforts for a given biocatalytic reaction. (c) 2006 Elsevier Ltd. All rights reserved