Stabilization of D-Amino Acid Oxidase via Covalent Immobilization and Mathematical Model of D-Methionine Oxidative Deamination Catalyzed by Immobilized Enzyme

Porcine kidney D-amino acid oxidase was stabilized by covalent immobilization on spherical particles of Eupergit C because of its low stability in soluble form. The focus of this work was to evaluate operational stability of the immobilized enzyme. To evaluate D-amino acid oxidase’s operational stability during process conditions, repetitive batch reactor experiments of D-methionine oxidation reaction were carried out with continuous aeration for oxygen supply at air-flow rates of 5 and 10 dm3 h–1. Kinetic analysis of the immobilized enzyme was done as well. The mathematical model of D-methionine oxidative deamination catalyzed by the immobilized D-amino acid oxidase was developed and it described the data well. It enabled the estimation of operational stability decay rate constant. It was possible to achieve 100 % substrate conversion in all batch experiments

Modelingof the Biotransformation Processes

Modeling and simulation of biotransformation processes have a large potential in searching for optimal process conditions, development and process design, control, scale-up, identifying of the process cost structure, and comparing process alternatives. Modeling and simulation leads to better understanding and quantification of the investigated process and could lead to significant material and costs savings especially in the early phases of the process development. In this review modeling and simulation techniques are demonstrated on two basically different types of bioprocesses, enzymatic and microbial biotransformations. Acetophenone reduction catalyzed by ADH from Thermoanaerobacter sp., amino acid oxidation catalyzed by D-amino acid oxidase from Arthrobacter protophormiae, and L-DOPA oxidation catalyzed by L-amino acid oxidases from Crotalus adamanteus and Rhodococcus opacus are examples for modeling of enzymatic biotransformation processes. On the other hand, microbial biotransformation processes are shown for: production of alcohol dehydrogenase (ADH) in baker\u27s yeast growing cells, production of L-malic acid by permeabilized non-growing yeast cells, production of 2,5-diketo-D-gluconic acid using Pantoea citrea, and for Escherichia coli based pyruvate production

Modelling and Optimization of the (R)-(+)-3,4-dihydroxyphenyllactic Acid Production Catalyzed with D-lactate Dehydrogenase from Lactobacillus leishmannii Using Genetic Algorithm

A mathematical model for the enzymatic kinetics of the synthesis of (R)–(+)–3,4-dihydroxyphenyllactic acid (DHPL) was developed. The synthesis was catalyzed by D-lactate dehydrogenase from Lactobacillus leishmannii. Since this enzyme requires NADH as a coenzyme, formate dehydrogenase system was used for NADH regeneration. Kinetic constants of both enzymes were estimated independently from initial reaction rate experiments. The developed mathematical model was verified by the batch reactor experiment (volumetric productivity in this experiment was 4.76 g dm–3 d–1). Optimization of initial reaction conditions for DHPL synthesis was performed using the genetic algorithm (GA). The genetic algorithm as a flexible optimization tool had been used to obtain the experimental conditions where maximal volumetric productivity could be achieved. The optimal initial conditions were found in the investigated parameter area: c3,4-dihydroxyphenylpyruvic acid = 4.69 mmol dm–3, cNAD+= 4.95 mmol dm–3, cformate = 36.85 mmol dm–3, D-lactate dehydrogenase = 3 mg cm–3, formate dehydrogenase = 2.94mg cm–3 and the reaction time 8.5 min. At these conditions volumetric productivity of 93.06 g dm–3 d–1 can be achieved

Benefits of reaction engineering in biocatalysis

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Konstrukcija mehaničkog pogona visokotlačne pumpe za ubrizgavanje goriva

U sklopu ovog završnog rada proučene su osnove rada common rail sustava ubrizgavanja goriva i osmišljeno je moguće konstrukcijsko rješenje mehaničkog pogona visokotlačne pumpe za ubrizgavanje goriva. U laboratoriju za motore i vozila nalazi se eksperimentalni postav motora s unutarnjim izgaranjem kojeg je potrebno opremiti odgovarajućim sustavom dobave goriva koji će omogućiti rad s Dieselovim načinom izgaranja. Ključni dio tog sustava je i visokotlačna pumpa prilagođena za common rail sustav ubrizgavanja koju je bilo potrebno odabrati na temelju zahtjeva motora tj. potrebnog protoka goriva te montirati na eksperimentalni postav tako da se pogon pumpe ostvaruje mehaničkim putem. Proučeno je nekoliko mogućih izvedbi pogona pumpe, a kao konačno rješenje je odabran pogon zupčastim remenom jer se pokazao najprikladniji za tu primjenu. Za odabrano rješenje je napravljeno konstrukcijsko rješenje u CAD alatu(modeli) te tehnička dokumentacija elemenata pogona. Isto tako napravljeni su potrebni proračuni elemenata pogona