Packaging materials account for 40% of Europe’s annual 50 million tons of plastic demand, and are primarily used in food applications. Their short lifespan and increasing usecontribute significantly to environmental pollution. Mechanical recycling addresses only a small portion of food packaging waste due to the complexity of mixed-polymer packaging. These unsorted blends exhibit poor mechanical, thermal, and optical properties, rendering conventional recycling methods inefficient. Although incineration provides energy recovery, it contradicts circular economy principles, while chemical recycling lacks economic feasibility and fails in specificity for plastic mixtures containing polymers of the same type, such as polyesters. Enzymatic recycling offers a promising, sustainable alternative. This selective depolymerization method can address challenges associated with complex packaging waste streams by enabling the targeted breakdown of polymers like PLA and PET.

Herein, 17 serine hydrolase enzymes (esterases and proteases), both in-house and commercial, were investigated for their specificity in polyester degradation. In-house enzymes were heterologously expressed in Escherichia coli or Pichia pastoris and their degradation potential was tested through reactions with semi-crystalline PET and two PLA grades: semi-crystalline PLLA and amorphous PDLLA. The degradation yield was evaluated by measuring the variation in molecular weight, through Gel Permeation Chromatography (GPC) for PLA and the concentration of hydrolysis products, and through High Performance Liquid Chromatography (HPLC) for PET.

The results show that most esterases cannot distinguish between PET and PLA, while proteases are specific to PLA. LCC^ICCG was the most efficient PETase (15 μg_prod/mg_PET) that could not degrade PLA, while Protease K and Savinase effectively degraded both amorphous (M_w,reduction = 16.5 %) and semi-crystalline (M_w,reduction = 28.2 %) PLA, respectively, but not PET.

Consequently, the treatment of packaging waste streams with the aforementioned PETase and PLAases could lead to the selective degradation of these polymers, purifying the mixture and facilitating further recycling, providing a sustainable pathway for advancing plastic waste management.

Nowadays, plastic pollution represents one of the most pressing environmental challenges, with millions of tons of synthetic polymers accumulating worldwide in landfills as well as in water bodies. Polyethylene terephthalate (PET), widely used in packaging and textiles, is resistant to natural degradation, while polylactic acid (PLA), although considered biodegradable, requires specific industrial conditions. Biological approaches, particularly those utilizing fungal strains, offer a sustainable alternative for addressing plastic waste. In this study, thirteen fungal strains were screened for their ability to grow on solid media containing chemically treated PET or PLA as the sole carbon source. The two most promising strains, Fusarium oxysporum BPOP18 and Aspergillus parasiticus MM36, demonstrated significant growth and polymer clearance halos on both PET and PLA solid media. However, enzymatic assays in liquid cultures revealed notable protease and esterase activity only in the presence of PLA, while in the presence of PET, the fungi showed no detectable enzymatic activity. To further investigate the enzymatic mechanisms underlying PLA degradation, proteomic analysis was conducted on the secretome of both fungi from PLA cultures. This revealed the presence of key proteins potentially involved in PLA breakdown, providing insights into enzymatic pathways and supporting the development of fungal-based biotechnological solutions for plastic waste management.

Hypercholesterolemia is a metabolic syndrome characterized by high levels of cholesterol in the blood plasma. Individuals with this condition have a significantly increased risk of developing cardiovascular diseases. Currently, natural or synthetic statins are prescribed to reduce cholesterol levels. In the synthesis of statin precursors, aldolases are often used. These are enzymes that catalyze the reversible and stereospecific aldol addition reaction between carbonyl compounds, forming chiral β-hydroxyketones or β-hydroxyaldehydes.

Among these enzymes, 2-deoxyribose-5-phosphate aldolase (DERA), which is acetaldehyde-dependent, can catalyze two consecutive aldol additions with absolute stereoselectivity, producing chiral 2,4,6-trideoxyhexoses that spontaneously cyclize into 2,4,6-trideoxy-D-erythro-hexapyranoses. However, a limitation of using DERA is that it becomes inhibited at high acetaldehyde concentrations, posing a challenge for large-scale reactions.

To obtain new statin precursors, we tested the activity of a genetically modified variant of DERA from Pectobacterium atrosepticum, showing a high tolerance to high concentrations of acetaldehyde, on crossed aldol addition reactions between acetaldehyde and aldehyde-based scaffolds derived from nitrogen-containing heterocycles, such as benzimidazole and substituted 4-phenyl-imidazoles, synthesized in our laboratory. The obtained products were analyzed using chromatographic and spectroscopic methods.

By replacing the heteroaromatic ring of commercial statins with different scaffolds, it may be possible to develop new hypocholesterolemic drugs that are more effective and have fewer side effects.

The increasing environmental burden of synthetic polymer waste has intensified the need for sustainable solutions to plastic pollution ^[1]. Microbial enzymes, particularly those from fungal strains, are emerging as promising biotechnological tools for waste circularity ^[2]. White-rot fungi, known for producing ligninolytic enzymes (oxidases and hydrolases), can degrade complex polymers (lignin, cutin, waxes, plastics) by disrupting their chemical structure ^[3,4]. This study investigates a strain of the order Agaricales (Basidiomycota), previously isolated from a Greek habitat and identified through ITS rRNA gene sequencing, that has shown great potential for plant-litter degradation but remains largely unexplored in terms of the depolymerization of xenobiotic polymers (plastics). The strain was tested for its ability to grow on polyester- or polyether-polyurethane (Impranil® DLN-SD, Impranil® DL 2077) as the sole carbon source, demonstrating efficient substrate degradation and high biomass yield. To explore the underlying biodegradation mechanism, a spectrophotometric assessment of extracellular enzymatic activities (hydrolases and oxidative enzymes) on Impranil® DLN-SD culture supernatants was performed; the results indicated high oxidative enzyme activity. Substrate modifications were detected through attenuated total reflectance–Fourier-transform infrared spectroscopy (ATR-FTIR), while gas chromatography–mass spectrometry (GC-MS) analysis was performed to identify the biodegradation products. Proteomic analysis of culture supernatants was conducted to identify and quantify enzymes involved in polymer degradation. This study highlights the potential of this strain as an effective biocatalyst for polymer degradation, providing a sustainable approach to plastic waste management and byproduct valorization.

Lignocellulosic biomass, a readily available and abundant organic material, is an ideal source of high-value compounds that can replace petroleum-based products. Among these, 5-hydroxymethylfurfural (HMF), obtained by the catalytic dehydration of biomass sugars ^[1], is a significant intermediate that can be converted into valuable compounds, including 2,5-furandicarboxylic acid (FDCA), a promising precursor for biopolymers ^[2]. Biocatalysis offers an environmentally friendly and efficient alternative to traditional chemical methods ^[3-5]. This study explores the biotransformation of HMF towards its oxidized derivatives using novel fungal enzymes from the Auxiliary Activity family AA5 of the CAZy database. Using the targeted exploration of fungal genomes, two promising enzymes, a glyoxal oxidase (GlGlyOx) and a galactose oxidase (FoGalOx), were identified and expressed heterologously in Pichia pastoris. The recombinant proteins were purified and tested for their ability to oxidize model furans (HMF and its derivative compounds). Our results reveal that both enzymes facilitate the production of oxidized monomers, with GlGlyOx showing efficiency in the biotransformation of HMF to 5-hydroxy-2-furancarboxylic acid (HMFCA) and furan-2,5-dicarbaldehyde (DFF) to 5- formylfurancarboxylic acid (FFCA), while FoGalOx was more efficient in oxidizing HMF to DFF and HMFCA to FFCA. The enzymes were also tested for their ability to transform HMF obtained from real biomass hydrolysates from OxiOrganosolv pretreated wheat straw pulps ^[6] via enzymatic saccharification and isomerization, followed by catalytic dehydration in mild conditions. Various acidic catalysts, including homogeneous (heteropolyacids, organic acids) and heterogeneous (zeolites, supported heteropolyacids) systems, were evaluated for their efficiency in dehydrating sugars to furans. The results highlight that the type and ratio of Brønsted to Lewis acidity play a key role in determining the reaction pathways for sugar conversion, significantly influencing the product distribution. This work demonstrates the potential of enzymatic biotransformation as a sustainable route for converting lignocellulosic biomass into valuable chemicals for green polymer production and other industrial applications.

The contamination of aquatic systems by synthetic dyes, such as malachite green, poses significant environmental and health risks due to their toxicity and persistence. In this study, we investigated the catalytic oxidation of malachite green using illite impregnated with iron (Fe) and indium (In) as a heterogeneous catalyst. The catalyst was synthesized through a wet impregnation method, ensuring the effective dispersion of metal ions on the illite clay surface. Comprehensive characterization of the material was conducted using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM-EDX) to elucidate its structural, morphological, and chemical properties.

The catalytic oxidation process was evaluated under various conditions, including varying the dye concentration, pH, and reaction temperature, to optimize the degradation efficiency. The Fe/In-illite catalyst achieved a degradation rate of over 97% for malachite green within a short reaction time under the optimal conditions. Kinetic studies revealed a pseudo-first-order reaction mechanism. The dual functionality of iron and indium provided a synergistic effect, enhancing the catalytic activity through effective electron transfer and oxidation pathways.

This work highlights the potential of Fe/In-illite as a cost-effective and environmentally friendly catalyst for the removal of toxic dyes from wastewater. Its application could contribute significantly to sustainable wastewater management and environmental remediation efforts.

Woodchips serve as a renewable and important readily available by-product of the forestry and timber sectors that can be utilized as biofuels through several methods, one of which is biocatalysis. The recent developments in biocatalysis have greatly increased the efficiency of converting wood chips into usable biofuels. Biocatalytic techniques utilize enzymes, microorganisms, and biocatalysts to decompose the intricate lignocellulosic structure of wood chips into fermentable sugars, bioethanol, biobutanol, or other forms of biofuels. The woodchips are primarily composed of cellulose, hemicellulose, and lignin, which are intricate polymers that are converted into biofuels. Prior to the biocatalysis process, woodchips typically undergo a pre-treatment process to break the lignin and other structural elements, allowing the cellulose and hemicellulose to unbind for better enzymatic breakdown. Some researchers are concentrating on producing biocatalysts which are capable of degrading both cellulose and lignin at the same time, which improves the overall process. For instance, modified enzymes or fungi such as Trichoderma reesei or species of Penicillium are utilized to improve cellulose hydrolysis, while microbes that degrade lignin are being modified for effective lignin decomposition. Enzymatic reactions play a crucial role in enhancing the efficiency of this conversion, and advancements in the development of biocatalysts are further enhancing the economic and technical viability of using woodchips as a biofuel source. This study examines the significance of biocatalysis in enhancing the conversion of wood chips into biofuels, emphasizing key enzyme systems such as cellulases and lignin-degrading enzymes that aid in the breakdown of cellulose, hemicellulose, and lignin components.

Lignocellulosic biomass is a composite material consisting of cellulose, hemicellulose, and lignin. Xyloglucan is a complex, highly substituted plant biomass hemicellulose that covers cellulose fibrils. Xyloglucanases, the enzymes responsible for its degradation, can be utilized for the design of efficient bioprocesses by incorporating them in enzyme cocktails that target cellulose-containing substrates. In order to shed light on the enzymatic degradation of xyloglucan, a novel xyloglucanase was studied from the basidiomycete Abortiporus biennis. Initially, a bioinformatic analysis of the xyloglucanase was carried out based on its amino acid sequence, followed by the heterologous production of AbiXega with the methylotrophic yeast P. pastoris acting as the host. Afterwards, the enzyme was purified to determine its biochemical and catalytic properties. Finally, its activity was investigated in 2 lignocellulose substrates (apple pulp, corn bran) to determine the synergism of AbiXega with a commercial cellulase preparation. From the results of these experiments, AbiXega was found to be a monomeric glycoprotein with a β-jelly roll structure with relatively strict substrate specificity, since it is only active in xyloglucan and β-glucan in an endo-dissociative way. The main hydrolysis products were the oligomers XXXG, XLXG/XXLG, and XLLG, and the optimum activity conditions are pH 4.5 and 55 ^oC. AbiXega was applied together with cellulases on the saccharification of corn bran and apple pulp. Overall, the importance of xyloglucanases on the saccharification of xyloglucan-containing substrates was demonstrated in this study. The results could contribute to the design of more efficient, tailor-made enzyme cocktails for the saccharification and subsequent valorization of lignocellulose.

The development of effective technologies for processing lignin has become a main area of interest in recent decades. An effective method that can be used for the conversion of lignocellulosic raw materials is pyrolysis. To establish the mechanisms of lignin decomposition under catalytic pyrolysis conditions, it is important to study the interaction of its macromolecule with the catalyst, as well as to study the thermal transformations of the lignin model compounds, cinnamic acids. Therefore, we studied the complexes of 4-methoxy cinnamic acid (4MCA) with the surface of nanoceria and the pyrolysis mechanisms of the formed complexes. The catalyst was impregnated with an ethanol solution of 4MCA. The obtained samples were investigated using the IR–Fourier spectroscopy method. Their thermal transformations were investigated using temperature-programmed desorption mass spectrometry using a МKH-7304А monopole mass spectrometer (Sumy, Ukraine) with electron impact ionization, which was adapted for thermodesorption measurements. In the 4MCA/СеО₂ samples, absorptions were detected at about 1398, 1495, and 1537 cm^‒1, which corresponded to the vibrations of the СОО^‒ group. The FTIR data indicate that 4MCA forms carboxylate complexes with bidentate bridge and chelate structures. In addition, the spectra revealed signs of interaction of the methoxyl group with nanoceria. Thermal decomposition of carboxylate complexes takes place in the temperature range of 100оС‒400^оС, which was confirmed based on the TPD peaks for the molecular and fragment ions of the pyrolysis products with m/z 107, 135, 150, and 160. The processes of decarbonylation, decarboxylation, and dehydration accompanied it. Decomposition products that may correspond to the destruction of complexes formed with the participation of methoxyl groups (m/z 31, 148, 164) when recorded above 250^oС. The obtained results may be useful for understanding the mechanisms of pyrolysis of lignin using nanoceria.

Acknowledgments

This research has received funding through the EURIZON project, which is funded by the European Union under grant agreement No.871072.

The production of biodiesel from microalgae presents a sustainable and renewable solution to the growing global energy demands, with catalysts playing a critical role in optimizing the transesterification process. This review examines the emerging catalysts and innovative techniques utilized in converting microalgal lipids into fatty acid methyl esters, emphasizing their impact on reaction efficiency, yield, and environmental sustainability. Catalysts are integral to the transesterification process, facilitating the conversion of lipids into biodiesel while reducing processing time and energy requirements. Homogeneous catalysts, such as sulfuric acid and sodium hydroxide, are widely used for their high reactivity and cost-effectiveness. Sulfuric acid demonstrates excellent performance in in situ transesterification, achieving biodiesel yields of 73% and 92% from Nannochloropsis oculata and Chlorella sp., respectively. However, the difficulty in separating these catalysts from the reaction mixture increases operational costs and environmental concerns. Heterogeneous catalysts offer a promising alternative due to their reusability and ease of separation. Examples include NaOH/zeolite, which has achieved biodiesel yields exceeding 98%, and KF/CaO, which demonstrated a yield of 93.07% when coupled with advanced techniques like ultrasound and microwave irradiation. Metal oxides such as CuO, NiO, and MgO supported on zeolite, as well as ZnAl-layered double hydroxides (LDHs), further enhance reaction performance through their high activity and stability. Enzymatic catalysts, particularly immobilized lipases, provide a more environmentally friendly option, offering high yields (>90%) and the ability to operate under mild conditions. However, their high cost and limited reusability pose significant challenges. Meanwhile, ionic liquid catalysts, such as tetrabutylphosphonium carboxylate, streamline the process by eliminating the need for drying and lipid extraction, achieving yields as high as 98% from wet biomass.