Dual Valorization of Lignin as a Versatile and Renewable Matrix for Enzyme Immobilization and (Flow) Bioprocess Engineering

Jean Thierry C Behaghel de Bueren, Stefania Bertella, Jeremy Luterbacher
WILEY-V C H VERLAG GMBH, 2021
Article

Résumé

Lignin has emerged as an attractive alternative in the search for more eco-friendly and less costly materials for enzyme immobilization. In this work, the terephthalic aldehyde-stabilization of lignin is carried out during its extraction to develop a series of functionalized lignins with a range of reactive groups (epoxy, amine, aldehyde, metal chelates). This expands the immobilization to a pool of enzymes (carboxylase, dehydrogenase, transaminase) by different binding chemistries, affording immobilization yields of 64-100 %. As a proof of concept, a omega-transaminase reversibly immobilized on polyethyleneimine-lignin is integrated in a packed-bed reactor. The stability of the immobilized biocatalyst is tested in continuous-flow deamination reactions and maintains the same conversion for 100 cycles. These results outperform previous stability tests carried out with the enzyme covalently immobilized on methacrylic resins, with the advantage that the reversibility of the immobilized enzyme allows recycling and reuse of lignin beyond the enzyme inactivation. Additionally, an in-line system also based on lignin is added into the downstream process to separate the reaction products by catch-and-release. These results demonstrate a fully closed-loop sustainable flow-biocatalytic system based exclusively on lignin.

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https://infoscience.epfl.ch/record/287292?ln=fr

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Hydrogénation sélective du 2-butyne-1,4-diol avec des catalyseurs de palladium supportés sur des matériaux filamenteux structurés

Eric Joannet

The principal objective of this thesis is the development of a palladium catalyst supported on woven fabrics of activated carbon fibers (ACF) for the reactions of hydrogenations in liquid phase and the design of multiphase reactors using the characteristics of these structures. This work was focused on Preparation, characterization and optimization of catalysts supported on the woven fabrics of activated carbon fibers; The intrinsic kinetics of the selective hydrogenation of 2-butylene-1,4-diol to 2-butyne-1,4-diol as model reaction; The comparison of the activity of our structured catalyst with that of commercial catalysts; Increase the catalyst concentration in the multiphase reactors with the design of a loop reactor containing a bubble column staged with the fiber fabrics supporting the catalyst, its characterization and the startup of this loop reactor which can operate in continuous or in batch mode. Chapter 4 presents the methods of manufacture of our palladium catalysts supported on woven structures of activated carbon fibers, their reproducibility and their homogeneous deposition. The characteristics of the support such as its handiness, its resistance to mechanical forces, the opening of its surface to liquid flow, its great specific surface area and its homogeneous distribution of micropores are defined there. The deposition of nanoparticules of active phase (0.5-5%mass) is characterized by metal surface obtained (280-87 m2/g), the dispersion of this surface (62.8-19.6%) and the average diameter of the nanoparticles (1.78-5.72 nm). The total degree of initial reduction (before reaction) was confirmed. Chapter 5 is devoted to the study of the reaction of selective hydrogenation of the 2-butyne-1,4-diol (B3) to 2-butylene-1,4-diol (B2) with a commercial palladium catalyst supported on activated carbon powder. A zero value even slightly negative was found for B3 partial order and equal to one for hydrogen. The activity obtained for this catalyst is large (37.1 mol(H2)/h gPd) but its initial selectivity is particularly low (SB3,0 = 76.8 %). Effect of support was tested and highlighted. Two supports (CaCO3 and Al2O3) gave reaction rates approximately half the size of those of the carbon support, but an initial selectivity close to 99 %. In chapter 6, selective hydrogenation in an autoclave with an agitator containing structured catalyst is tested. This reactor is first of all evaluated like a reactor working in kinetic mode for the selected reaction. Kinetics was studied and showed that the fibrous support does not change the orders of reaction compared to the commercial catalyst. Energy of activation of 30 kJ/mol was found in the studied configuration. A variation of the catalytic amount on woven structure was studied and gave a reaction rate of 19.4 (mol(H2)/h gPd) for an initial selectivity of 98 % for the best catalyst (Pd(2%)/ACF). The reuse of this catalyst with an in situ reactivation in hydrazine allowed a stabilization of the activity at 50% of the initial activity after four experiments. A constant Turn Over Frequency (TOF) for catalysts with high deposits (2-5%) was given. An increase in the TOF for the low deposits (0.5% and 1%) was found. This increase in the TOF agrees with a fall of the initial selectivity. The effect of several variables of the reaction such as pressure, temperature and pH of the solution were examined. Within the framework of the variation of pH an initial selectivity of 100% and selectivity during reaction remaining higher than 95% until a conversion of 90 % were obtained. This profit of selectivity was achieved only with the detriment to the reaction rate which decreased by a factor 2.5. Finally, experiments with even less harm to the environment were made without solvent thus allowing the avoidance of purification. The rate of hydrogenation in this configuration is very high (79.2 mol(H2)/(h gPd)). But in this configuration, this increase in activity is not done at the expense of the initial selectivity (98 %). In chapter 7, the increase in the catalyst concentration in the reactor was required for higher productivity. For that purpose, a new concept of reactor was studied. This new reactor is a loop reactor containing a bubble column staged with woven catalytical structure. The pressure drop, the emulsion crossing the bubble column and the RTD were characterized. The reactor, functioning in batch or continuous mode, was studied. The productivity in batch was improved by an order of magnitude due to the increase in the catalytic concentration. A unit worked during 50 hours continuously without deactivation of catalyst providing 160 g of B2 per hour (> 1 tons/year). The reaction led to a conversion of 85% with a selectivity of 96 %.

EPFL2005

Chargement

New drugs are needed to assure effective therapies for previously untreated diseases, emerging diseases, and personalized medicine, but the process of drug development is complex, costly, and time-consuming. This is especially problematic considering that 90% of drug candidates in clinical trials are discarded due to unexpected toxicity or other secondary effects. This inefficiency threatens our health care system and economy. Despite the advances in the cellular metabolism, our knowledge of the mechanisms governing enzymatic biotransformations in cells is far from complete, in particular regarding degradation pathways, mode of action, or side effects of drugs. Examining the mechanisms of enzymatic reactions at the cellular scale could improve our fundamental understanding of their catalytic capability, and facilitate identifying and filling the knowledge gaps. The scale and the complexity of metabolic data is ever-expanding, requiring scientists to apply more advanced computational methods to systematically store, explore, and interpret the enzymatic potential of cells. The first step toward simulating enzymes in silico is to learn from their biochemical reactions in nature. To do this, we use distilled knowledge of known biochemistry in the form of generalized enzymatic reaction rules. Enzymatic rules are mathematical representations of enzymatic action mimicking the catalytic function of enzymes. They are formulated in a less specific manner (more promiscuous) to act on a broad range of substrates. In addition to reconstructing known biochemistry, the application of these reaction rules paves the way toward the discovery of novel enzymatic interactions. In this thesis, I developed computational models, tools, and methodologies to facilitate the study of metabolism and catalytic action of enzymes. We analyzed different aspects of metabolism through five distinct studies: In a first study, in order to provide a holistic view of currently known biochemistry, we gathered biochemical data from 14 sources, covering the known metabolic networks of all species. We integrated all biological data into a high-performance database based on ontology, named LCSB DB. We further expanded the scope of LCSB DB to cover all bioactive and chemicals. LCSB DB offers fast and efficient searching of biochemical data and serves as a platform for sharing, storing, and analyzing biochemical data. In a second study, we used enzymatic reaction rules to predict all theoretically possible metabolic reactions between biological and bioactive compounds in LCSB DB. In a third study, we developed a method to find enzymes are able to catalyze orphan and predicted reactions, called BridgIT. BridgIT uses the knowledge of reactive sites on substrates to find the most similar, known biochemical reactions. We then validated the utility of BridgIT in enzyme discovery for the design of de novo synthetic pathways producing tetrahydropalmatine and adipic acid. In the last study, we propose a workflow for rational drug design and systems-level analysis of drug metabolism, called NICEdrug.ch. NICEdrug.ch allows large-scale computational analysis of drug biochemistry (metabolic precursors or prodrugs and metabolic fate or degradation), enzymatic targets, and toxicity in the context of cellular metabolism. Finally, in the conclusion chapter, we discuss the contribution and the potential further applications of the computational tools that were developed in this thesis.

EPFL2020

Chargement

Hydrogénation sélective du 2-butyne-1,4-diol avec des catalyseurs de palladium supportés sur des matériaux filamenteux structurés

Eric Joannet

EPFL2005

EPFL2020