Fundamentals of bio-based technologies for selective metal recovery from bio-leachates and liquid waste streams.

The number of metal-containing waste streams resulting from electronic end-of life products, metallurgical by-products, and mine tailings to name but a few, is increasing worldwide. In recent decades, the potential to exploit these waste streams as valuable secondary resources to meet the high demand of critical and economically important raw materials has become more prominent. In this review, fundamental principles of bio-based metal recovery technologies are discussed focusing on microbial metabolism-dependent and metabolism-independent mechanisms as sustainable alternatives to conventional chemical metal recovery methods.

Enzyme Benchmarking with Polyethylene Furanoate Soluble Scaffolds for Directed Evolution of PEFases.

Plastic waste is a major threat in our industrialized world and is driving research into bioplastics. The success of biobased polyethylene furanoate (PEF) as a viable alternative to polyethylene terephthalate (PET) of fossil origin will depend on designing effective enzymes to break it down, aiding its recycling. Here, a panel of fungal and bacterial cutinases were functionally expressed in a tandem yeast expression system based on and .

Xylose Acetals - a New Class of Sustainable Solvents and Their Application in Enzymatic Polycondensation.

The use of organic solvents in academic research and industry applications is facing increasing regulatory pressure due to environmental and health concerns. Consequently, there is a growing demand for sustainable solvents, particularly in the enzymatic synthesis and processing of polyesters. Biocatalysts offer a sustainable method for producing these materials; however, achieving high molecular weights often necessitates use of solvents.

Detoxification of aflatoxin B1 by a spore coat protein through formation of the main metabolites AFQ1 and epi-AFQ1.

A variety of important agricultural crops host fungi from the genus can produce cancerogenic secondary metabolites such as aflatoxins. Consequently, novel strategies for detoxification and their removal from food and feed chains are required. Here, detoxification of Aflatoxin B1 (AFB1) by the multi-copper oxidase CotA (BsCotA) was investigated.

Recovery of pure PET from wool/PET/elastane textile waste through step-wise enzymatic and chemical processing.

Textile waste is mostly incinerated because few recycling processes are available to recover valuable materials. In this work, a feasible chemo-enzymatic recycling process of wool/polyethylene terephthalate (PET)/elastane blends to recover pure PET is for the first time successfully demonstrated. Two novel enzyme formulations were selected for wool hydrolysis, whereas the recovered amino acids were quantified using high-performance liquid chromatography and two assays (Ninhydrin and Folin-Ciocalteu).

Controlled Enzymatic Synthesis of Polyesters Based on a Cellulose-Derived Triol Monomer: A Design of Experiment Approach.

Regioselective enzymatic polycondensation of the bio-based cellulose derived polyol, Triol-citro, and dimethyl adipate using Candida antarctica Lipase B (CaLB) was investigated. A Design of Experiment approach with MODDE® Pro 13 was used to determine important factors in the branching behavior of this polymer, and reactant ratio, temperature, reaction time and enzyme wt % were the studied factors. Multifunctional polyesters with pendant hydroxy groups were synthesized and fully characterized using 2D NMR techniques to determine degree of branching.

Spent brewer's yeast as a selective biosorbent for metal recovery from polymetallic waste streams.

While the amount of electronic waste is increasing worldwide, the heterogeneity of electronic scrap makes the recycling very complicated. Hydrometallurgical methods are currently applied in e-waste recycling which tend to generate complex polymetallic solutions due to dissolution of all metal components. Although biosorption has previously been described as a viable option for metal recovery and removal from low-concentration or single-metal solutions, information about the application of selective metal biosorption from polymetallic solutions is missing.

Effect of Salts on Laccase-Catalyzed Polymerization of Lignosulfonate.

Enzymatic polymerization of lignosulfonate (LS) has a high potential for various applications ranging from coatings to adhesives. Here, the effect of different ions in low concentrations on enzymatic polymerization of LS was investigated, including salt solutions consisting of mono- and dicarboxylic acids, sulfate, phosphate and chloride with sodium as counter ion. LS polymerization was followed by viscometry and size exclusion (SEC) chromatography.

Metal recovery from spent lithium-ion batteries via two-step bioleaching using adapted chemolithotrophs from an acidic mine pit lake.

The demand for lithium-ion batteries (LIBs) has dramatically increased in recent years due to their application in various electronic devices and electric vehicles (EVs). Great amount of LIB waste is generated, most of which ends up in landfills. LIB wastes contain substantial amounts of critical metals (such as Li, Co, Ni, Mn, and Cu) and can therefore serve as valuable secondary sources of these metals.

Multifunctional Casein-Based Wound Dressing Capable of Monitoring and Moderating the Proteolytic Activity of Chronic Wounds.

Every 1.2 s, a diabetic foot ulcer is developed, and every 20 s, one amputation is carried out in diabetic patients. Monitoring and controlling protease activity have been considered as a strategy for more efficient management of diabetic and other chronic wounds.

Laccase-mediated degradation of petroleum hydrocarbons in historically contaminated soil.

Laccases (EC1.10.3.

On the Selective Enzymatic Recycling of Poly(pentamethylene 2,5-furanoate)/Poly(lactic acid) Blends and Multiblock Copolymers.

Among novel renewable furanoate-based polyesters, poly(pentamethylene 2,5-furandicarboxylate) (PPeF) shows outstanding gas barrier properties and high flexibility. PPeF blending/copolymerization with another well-known bio-based polymer, poly(lactic acid) (PLA), leads to considerably better mechanical and gas barrier properties of the latter, making it suitable for flexible food packaging applications. In this work, enzymatic depolymerization of PLA/PPeF blends with different compositions (1, 3, 5, 20, 30, and 50 wt % PPeF) and a PLA-PPeF block copolymer (50 wt % PPeF) by cutinase 1 from (Thc_Cut1) was investigated as a possible recycling strategy.

Dihydropyrimidinase from can hydrolyse polyamides.

In dihydropyrimidinase (DHPaseSK) is involved in the pyrimidine degradation pathway, which includes the reversible ring cleavage between nitrogen 3 and carbon 4 of 5,6-dihydrouracil. In this study, DPHaseSK was successfully cloned and expressed in BL-21 Gold (DE3) with and without affinity tags. Thereby, the Strep-tag enabled fastest purification and highest specific activity (9.

Engineering a Carboxyl Methyltransferase for the Formation of a Furan-Based Bioplastic Precursor.

FtpM from Aspergillus fumigatus was the first carboxyl methyltransferase reported to catalyse the dimethylation of dicarboxylic acids. Here the creation of mutant R166M that can catalyse the quantitative conversion of bio-derived 2,5-furandicarboxylic acid (FDCA) to its dimethyl ester (FDME), a bioplastics precursor, was reported. Wild type FtpM gave low conversion due to its reduced catalytic efficiency for the second methylation step.

Bio-upcycling of multilayer materials and blends: closing the plastics loop.

The urge to discover and develop new technologies for closing the plastic carbon cycle is motivating industries, governments, and academia to work closely together to find suitable solutions in a timely manner. In this review article, a combination of uprising breakthrough technologies is presented highlighting their potential and complementarity to be integrated one with the other, therefore providing a potential solution to efficiently solve the plastics problem. First, modern approaches for bio-exploration and engineering of polymer-active enzymes are presented to degrade polymers into valuable building blocks.

The Biomodified Lignin Platform: A Review.

A reliance on fossil fuel has led to the increased emission of greenhouse gases (GHGs). The excessive consumption of raw materials today makes the search for sustainable resources more pressing than ever. Technical lignins are mainly used in low-value applications such as heat and electricity generation.

Improving Properties of Starch-Based Adhesives with Carboxylic Acids and Enzymatically Polymerized Lignosulfonates.

A novel strategy for improving wet resistance and bonding properties of starch-based adhesives using enzymatically polymerized lignosulfonates and carboxylic acids as additives was developed. Therefore, lignosulfonates were polymerized by laccase to a molecular weight of 750 kDa. Incorporation of low concentrations (up to 1% of the starch weight) of 1,2,3,4-butanetetracarboxylic acid (BTCA) led to further improvement on the properties of the adhesives, while addition of greater amounts of BTCA led to a decrease in the properties measured due to large viscosity increases.

Bioelectrochemical methanation by utilization of steel mill off-gas in a two-chamber microbial electrolysis cell.

Carbon capture and utilization has been proposed as one strategy to combat global warming. Microbial electrolysis cells (MECs) combine the biological conversion of carbon dioxide (CO) with the formation of valuable products such as methane. This study was motivated by the surprising gap in current knowledge about the utilization of real exhaust gas as a CO source for methane production in a fully biocatalyzed MEC.

Chitosan: Sources, Processing and Modification Techniques.

Chitosan, a copolymer of glucosamine and -acetyl glucosamine, is derived from chitin. Chitin is found in cell walls of crustaceans, fungi, insects and in some algae, microorganisms, and some invertebrate animals. Chitosan is emerging as a very important raw material for the synthesis of a wide range of products used for food, medical, pharmaceutical, health care, agriculture, industry, and environmental pollution protection.

Role of Surface Enhancement in the Enzymatic Cross-Linking of Lignosulfonate Using Alternative Downstream Techniques.

Lignosulfonate (LS), one of the byproducts of the paper and pulp industry, was mainly used as an energy source in the last decade until the valorization of lignin through different functionalization methods grew in importance. Polymerization using multicopper oxidase laccase (from the fungus) is one of such methods, which not only enhances properties such as hydrophobicity, flame retardancy, and bonding properties but can also be used for food and possesses pharmaceutical-like antimicrobial properties and aesthetic features of materials. Appropriate downstream processing methods are needed to produce solids that allow the preservation of particle morphology, a vital factor for the valorization process.

Optimized biogenic sulfuric acid production and application in the treatment of waste incineration residues.

The biological leaching of metals from different waste streams by bacteria is intensively investigated to address metal recycling and circular economy goals. However, usually external addition of sulfuric acid is required to maintain the low pH optimum of the bacteria to ensure efficient leaching. Extremely acidophilic Acidithiobacillus spp.

Enzymatic synthesis of wet-resistant lignosulfonate-starch adhesives.

This work describes a new method for improving the properties, mainly the wet-resistance, of starch-based adhesives using enzymatically polymerized lignosulfonates. A correlation of viscosity with molecular weight was found, allowing simple control of enzymatic polymerization of lignosulfonates. Incorporation of lignosulfonates polymerized from 29 kDa to > 4500 kDa using laccase led to a considerable increase in wet-resistance (from 15 to 20 min for the laminating glue and from 150 to 1200 min for the bag glue) while not affecting (for the laminating glue) or even improving the bonding time (from 80 to 60 s for the bag glue).

Cutinase-Catalyzed Polyester-Polyurethane Degradation: Elucidation of the Hydrolysis Mechanism.

Polyurethanes (PU) are one of the most-used classes of synthetic polymers in Europe, having a considerable impact on the plastic waste management in the European Union. Therefore, they represent a major challenge for the recycling industry, which requires environmentally friendly strategies to be able to re-utilize their monomers without applying hazardous and polluting substances in the process. In this work, enzymatic hydrolysis of a polyurethane-polyester (PU-PE) copolymer using cutinase (HiC) has been investigated in order to achieve decomposition at milder conditions and avoiding harsh chemicals.

Residue-Specific Incorporation of the Non-Canonical Amino Acid Norleucine Improves Lipase Activity on Synthetic Polyesters.

Environmentally friendly functionalization and recycling processes for synthetic polymers have recently gained momentum, and enzymes play a central role in these procedures. However, natural enzymes must be engineered to accept synthetic polymers as substrates. To enhance the activity on synthetic polyesters, the canonical amino acid methionine in lipase (TTL) was exchanged by the residue-specific incorporation method for the more hydrophobic non-canonical norleucine (Nle).