Evangelos Topakas

National Technical University of Athens | NTUA · School of Chemical Engineering

To investigate the interplay between substrate structure and enzymatic hydrolysis (EH) efficiency, poplar was pretreated with acidic sodium-chlorite (ASC), 3% sodium-hydroxide (3-SH), and 3% sulfuric acid (3-SA), resulting in different glucose yields of 94.10%, 74.35%, and 24.51%, respectively, of pretreated residues. Residues were fractionated int...

Furans, such as 5-hydroxymethylfurfural (HMF), are compounds of great importance that can serve as starting materials for the synthesis of polymers. Their production from lignocellulose-derived sugar streams offers a promising alternative to fossil fuels, while enabling biomass transformation to chemicals with higher value. In the present work, the...

Glycoside hydrolase (GH) 30 family xylanases are enzymes of biotechnological interest due to their capacity to degrade recalcitrant hemicelluloses, such as glucuronoxylan (GX). This study focuses on a subfamily 7 GH30, Tt Xyn30A from Thermothelomyces thermophilus , which acts on GX in an “endo” and “exo” mode, releasing methyl‐glucuronic acid branc...

The rapid escalation of plastic waste accumulation presents a significant threat of the modern world, demanding an immediate solution. Over the last years, utilization of the enzymatic machinery of various microorganisms has emerged as an environmentally friendly asset in tackling this pressing global challenge. Thus, various hydrolases have been d...

The discovery and engineering of novel biocatalysts capable of depolymerizing polyethylene terephthalate (PET) have gained significant attention since the need for green technologies to combat plastic pollution has become increasingly urgent. This study focuses on the development of novel substrates that can indicate enzymes with PET hydrolytic act...

Global plastic waste accumulation has become omnipresent in public discourse and the focus of scientific research. Ranking as the sixth most produced polymer globally, polyurethanes (PU) significantly contribute to plastic waste and environmental pollution due to the toxicity of their building blocks, such as diisocyanates. In this study, the effec...

This poster presents a pathway to deal with the problem of mixed plastic waste streams formed from petroleum- and bio-based plastics. Despite their ubiquitous presence in the environment, the vast majority of post-consumer plastics waste that is inherently mixed remains unrecycled, ending up incinerated or landfilled. Therefore, finding more sustai...

Background The field of enzymology has been profoundly transformed by the discovery of lytic polysaccharide monooxygenases (LPMOs). LPMOs hold a unique role in the natural breakdown of recalcitrant polymers like cellulose and chitin. They are characterized by a “histidine brace” in their active site, known to operate via an O2/H2O2 mechanism and re...

Ubiquitous post-consumer plastic waste is often physically mixed combining recalcitrant petroleum-based plastics with bioplastics, forming (petro-bio)plastic streams. Finding appropriate end-of-life (EoL) strategies for mixed (petro-bio)plastic waste is highly pertinent in achieving environmental protection, sustainability for plastic value chain i...

The growing global market of dairy products has led to the need for alternative approaches regarding whey valorization, which is the primary by-product of cheese and strained yogurt production. In this context, prebiotic galactooligosaccharides can be produced enzymatically from whey using commercially available β-galactosidases. A comparative stud...

The steadily increasing global popularity of Greek strained yoghurt has necessitated alternative valorization approaches for acid whey, the major straining process effluent. In this context, prebiotic galacto-oligosaccharides can be enzymatically synthesized from acid whey lactose, via either commercial or novel β-galactosidases. A comparative stud...

Exploring new solutions to improve the environmentally friendly degradation of fossil based postconsumer plastic waste is key in the development of effective techniques to increase the efficiency of plastics degradation while using mild, green depolymerization conditions. In this context, we introduce a novel, ultrafast mechanical pretreatment for...

(1) Background: Bacterial nanocellulose (BNC) has gained in popularity over the years due to its outstanding properties such as renewability, biocompatibility, and bioavailability, and its use as an eco-friendly material of the future for replacing petrochemical products. (2) Methods: This research refers to the utilization of lignocellulose coming...

Biotechnological treatment of plastic waste has gathered substantial attention as an efficient and generally greener approach for polyethylene terephthalate (PET) depolymerization and upcycling in comparison to mechanical and chemical processes. Nevertheless, a suitable combination of mechanical and microbial degradation may be the key to bringing...

Multicopper oxidases are promiscuous biocatalysts with great potential for the production of industrial compounds. This study is focused on the elucidation of the structure–function determinants of a novel laccase-like multicopper oxidase from the thermophilic fungus Thermothelomyces thermophila (TtLMCO1), which is capable of oxidizing both ascorbi...

Plastic pollution remains a significant environmental challenge, with conventional waste management strategies proving insufficient in addressing the problem. Enzymatic degradation has emerged as a promising alternative, with LCCICCG, an engineered metagenome-derived cutinase, being the most effective in degrading polyethylene terephthalate (PET),...

Exploring new solutions to improve the environmentally friendly degradation of fossil based postconsumer plastic waste is key in the development of effective techniques to increase the efficiency of plastics degradation while using mild, green depolymerization conditions. In this context, we introduce a novel, ultrafast mechanical pretreatment for...

Acetyl substitutions are common on the hemicellulosic structures of lignocellulose, which up until recently were known to inhibit xylanase activity. Emerging data, however, suggest that xylanases are able to accommodate acetyl side-groups within their catalytic site. In the present work, a fungal GH30 xylanase from Thermothelomyces thermophila, nam...

Feruloyl esterases (FAEs) hydrolyze the ester bonds between hydroxycinnamic acids and arabinose residues of plant cell walls and exhibit considerable diversity in terms of substrate specificity. Here, we report the crystal structure of an FAE from Fusarium oxysporum (FoFaeC) at 1.7 Å resolution in complex with p-coumaric acid, which is the first li...

The uncontrollable disposal of plastic waste has raised the concern of the scientific community, which tries to face this environmental burden by discovering and applying new techniques. Regarding the biotechnology field, several important microorganisms possessing the necessary enzymatic arsenal to utilize recalcitrant synthetic polymers as an ene...

Polyurethanes (PUs) are an exceedingly heterogeneous group of plastic polymers, widely used in a variety of industries from construction to medical implants. In the past decades, we have witnessed the accumulation of PU waste and its detrimental environmental impacts. PUs have been identified as one of the most toxic polymers leaching hazardous com...

Alternative sweeteners, such as steviol glucosides from the plant Stevia rebaudiana Bertoni, are becoming increasingly popular for the design of next-generation foodstuffs. However, the bitter aftertaste of native steviol glucosides is one of the main reasons behind consumer reluctance towards stevia-containing products. Biocatalysis could be a sus...

The role of carbon dioxide in our changing climate is now hard to ignore, and many countries are making pledges to reduce or eliminate their carbon output. Chemical valorisation of carbon dioxide, as an alternative to sequestration, is likely to play an important part in reaching these targets, and as such is one of the fastest developing areas of...

The milestone of the 10th anniversary of Catalysts is a great time to reflect on past accomplishments, present progress and challenges, as well as to identify future challenges and opportunities [...]

White-rot basidiomycetes are the only microorganisms able to produce both hydrolytic (cellulases and hemicellulases) and oxidative (ligninolytic) enzymes for degrading all lignocellulose constituents. Their enzymatic machinery makes them ideal for the discovery of novel enzymes with desirable properties. In the present work, Abortiporus biennis, a...

In this study, we examine the growth of four microalgae strains of Phaeocystis sp., Pleurochrysis sp., Chlorella sp. and Nannochloropsis sp. with Mediterranean origin, which have been poorly addressed in laboratory studies under autotrophic against mixotrophic and heterotrophic conditions. Our results demonstrate that in autotro-phic conditions, th...

Stevia rebaudiana Bertoni is becoming increasingly popular as a sweetener, due to its high steviol glycoside content. However, the bitter aftertaste of those compounds is an issue for consumers, which can be alleviated with the addition of glycosyl substituents to the molecule. β-Xylosidases are known to transxylosylate various acceptors, mostly al...

Lytic polysaccharide monooxygenases (LPMOs) are enzymes able to act on a great variety of polysaccharides by an oxidative cleavage mechanism, targeting not only crystalline substrates, such as cellulose and chitin, but also other amorphous structures including xylan, mannan, and pectin. The key role of LPMOs toward the isolation of nanocellulose fr...

Recovery of omega-3 fatty acids (FAs) from microalgae constitutes a valuable alternative to fish oil, and offers the ability to isolate a single ω-3 FA, instead of a mixture. In the framework of the concept of circular economy and sustainability, in the current work, an alternative carbon source was used as feed for oleaginous microalga Crypthecodi...

The uncontrolled release of plastics in the environment has rendered them ubiquitous around the planet, threatening the wildlife and human health. Biodegradation and valorization of plastics has emerged as an eco-friendly alternative to conventional management techniques. Discovery of novel polymer-degrading enzymes with diversified properties is h...

To date, the possibility of drug-resistant bacterial infections in hospitals and intensive care units comprises a significant concern especially for immunocompromised cancer patients. In the current study, violacein and superparamagnetic iron oxide nanoparticles were co-encapsulated in polylactic acid nanoparticles (vio-Fe 3 O 4 -PLA) and tested fo...

Effective interfacing of energy-efficient and biobased technologies presents an all-green route to achieving continuous circular production, utilization, and reproduction of plastics. Here, we show combined ultragreen chemical and biocatalytic depolymerization of polyethylene terephthalate (PET) using deep eutectic solvent (DES)-based low-energy mi...

Nanocellulose, either in the form of fibers or crystals, constitutes a renewable, biobased, biocompatible material with advantageous mechanical properties that can be isolated from lignocellulosic biomass. Enzyme-assisted isolation of nanocellulose is an attractive, environmentally friendly approach that leads to products of higher quality compared...

The market for pectinolytic enzymes is continually expanding. In addition to the food, animal feed, textile and paper industries, pectinases have recently found application in the field of biorefinery. However, the industrial production of these enzymes is associated with high costs. Thus, the search for new source of microbial enzymes with low cul...

The core objective of this work was to take advantage of the unexploited wheat straw biomass, currently considered as a broadly available waste stream from the Greek agricultural sector, towards the integrated valorization of sugar streams for the microbial production of polyunsaturated omega-3 fatty acids (PUFAs). The OxiOrganosolv pretreatment pr...

Crypthecodinium cohnii represents a heterotrophic microalga rich in omega-3 polyunsaturated fatty acids (PUFAs) with significant health benefits, and especially docosahexaenoic acid (DHA). In the present study, freeze-dried C. cohnii biomass, cultivated in fed-batch bioreactors with a feed of acetic acid 33% (v/v), was used. In the first set of exp...

The field of enzymatic degradation of lignocellulose is actively growing and the recent updates of the last few years indicate that there is still much to learn. The growing number of protein sequences with unknown function in microbial genomes indicates that there is still much to learn on the mechanisms of lignocellulose degradation. In this revi...

Background Over the last few years, valorization of lignocellulosic biomass has been expanded beyond the production of second-generation biofuels to the synthesis of numerous platform chemicals to be used instead of their fossil-based counterparts. One such well-researched example is 5-hydroxymethylfurfural (HMF), which is preferably produced by th...

Fungal xylanases belonging to family GH30_7, initially categorized as endo-glucuronoxylanases, are now known to differ both in terms of substrate specificity, as well as mode of action. Recently, TtXyn30A, a GH30_7 xylanase from Thermothelomyces thermophila, was shown to possess dual activity, acting on the xylan backbone in both an endo- and an ex...

The aim of this work was to investigate the use of isobutanol as organic solvent for the efficient delignification and fractionation of beechwood through the OxiOrganosolv process in the absence of any catalyst. The results demonstrate that cellulose-rich solid pulp produced after pretreatment is a source of fermentable sugars that can be easily hy...

In this work, a lytic polysaccharide monooxygenase (LPMO) belonging to the AA9 family from the filamentous fungus Thermothelomyces thermophilus, MtLPMO9H, is immobilized on cobalt functionalized multi-walled carbon nanotubes modified glassy carbon electrode. The step of the binding of phosphoric acid swollen cellulose on this LPMO is studied using...

Inspirational concepts, and the transfer of analogs from natural biology to science and engineering, has produced many excellent technologies to date, spanning vaccines to modern architectural feats. This review highlights that answers to the pressing global petroleum-based plastic waste challenges, can be found within the mechanics and mechanisms...

We describe herein the synthesis and laccase mediated oxidation of six novel 1,4-dihydropyridine (DHP)-based hexahydroquinolines (DHP1-DHP3) and decahydroacridines (DHP4-DHP6). We employed different laccase enzymes with varying redox potential to convert DHP1-DHP3 and DHP4-DHP6 to the corresponding pyridine-containing tetrahydroquinoline and octahy...

Stevia rebaudiana Bertoni is a plant cultivated worldwide due to its use as a sweetener. The sweet taste of stevia is attributed to its numerous steviol glycosides, however, their use is still limited, due to their bitter aftertaste. The transglycosylation of steviol glycosides, aiming at the improvement of their taste, has been reported for many e...

The establishment of a sustainable circular bioeconomy requires the effective material recycling from biomass and biowaste beyond composting/fertilizer or anaerobic digestion/bioenergy. Recently, volatile fatty acids attracted much attention due to their potential application as carbon source for the microbial production of high added-value product...

Lytic polysaccharide monooxygenases (LPMOs) consist of a class of enzymes that boost the release of oxidised products from plant biomass, in an approach that is more eco-friendly than the traditional ones, employing harsh chemicals. Since LPMOs are redox enzymes, they could possibly be exploited by immobilisation on electrode surfaces. Such an appr...

Polyphenol oxidases (PPOs) are an industrially relevant family of enzymes, being involved in the post-harvest browning of fruits and vegetables, as well as in human melanogenesis. Their involvement lies in their ability to oxidize phenolic or polyphenolic compounds, that subsequently form pigments. PPO family includes tyrosinases and catechol oxida...

The purpose of the present study was to develop an efficient, cost-effective process towards the valorization of medical cotton waste (MCW). Application of dilute acid pretreatment as an initial step partially degrades the cotton cellulosic fibers rendering the material more amenable to enzymatic hydrolysis towards the production of glucose. MCW wa...

The use of several lignocellulosic and other organic wastes has been considered in literature for the production of L-asparaginases (L-ASNase); however, the use of olive mill wastewater (OMWW) has never been contemplated as culture media. OMWW is a widely available waste in the Mediterranean that needs to be treated due to its high pollutant load....

The present work implements the encapsulation of the probiotic strain Bifidobacterium animalis subsp. lactis (BB-12) in various encapsulating mixtures through extrusion. The surface morphology of the beads produced, as well as the survival of the probiotics’ cells was evaluated during storage at 4 °C and −18 °C, and throughout the in vitro simulati...

Background Laccases and laccase-like multicopper oxidases (LMCOs) oxidize a vast array of phenolic compounds and amines, releasing water as a byproduct. Their low substrate specificity is responsible for their tremendous biotechnological interest, since they have been used for numerous applications. However, the laccases characterized so far corres...

On 28 December 2020, Prof. Dr. Peter Grunwald died after a short, serious illness. [...]

β-Galactosidases are key enzymes in the food industry. Apart from the hydrolysis of the saccharide bond of lactose, they also catalyze transgalactosylation reactions, producing galactooligosaccharides (GOS) with prebiotic activity. Here we report the heterologous production in Pichia pastoris of a novel β-galactosidase from the fungus Thermothielav...

Conversion of lignocellulose to sugar depends on expensive cellulase and xylanase, hence, improvement of enzyme utilization is important. Enzymatic kinetics can guide researchers toward efficient enzymes utilization. Based on Michaelis-Menten theory and enzyme deactivation reactions, the novel kinetic models describing sugar (glucose and xylose) yi...

Polyphenol oxidases (PPOs) are an industrially relevant family of enzymes, being involved in the post-harvest browning of fruits and vegetables, as well as in human melanogenesis. Their involvement lies in their ability to oxidize phenolic or polyphenolic compounds, that subsequently form pigments. PPO family includes tyrosinases and catechol oxida...

White-rot basidiomycetes are the only microorganisms with the ability to produce both hydrolytic (cellulases and hemicellulases) and oxidative (ligninolytic) enzymes for degrading cellulose/hemicellulose and lignin. In addition, they produce biologically active natural products with important application in cosmetic formulations, either as pure com...

Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs), that can be detected in a variety of environments including the human body, adversely affecting global health. Bioremediation is an emerging field for the detoxification and removal of environmental pollutants, with novel biocatalysts appropriate for this task being in high...

Polyethylene terephthalate (PET) is widely used material and as such became highly enriched in nature. It is generally considered inert and safe plastic, but due to the recent increased efforts to break-down PET using biotechnological approaches, we realized the scarcity of information about structural analysis of possible degradation products and...