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. Green enzyme-based modifications of technical lignin have generated a number of functional lignin-based polymers, fillers, coatings, and many other applications and materials. These bio-modified technical lignins often display similar properties in terms of their durability and elasticity as fossil-based materials while also being biodegradable. Therefore, it is possible to replace a wide range of environmentally damaging materials with lignin-based ones. By researching publications from the last 20 years focusing on the latest findings utilizing databases, a comprehensive collection on this topic was crafted. This review summarizes the recent progress made in enzymatically modifying technical lignins utilizing laccases, peroxidases, and lipases. The underlying enzymatic reaction mechanisms and processes are being elucidated and the application possibilities discussed. In addition, the environmental assessment of novel technical lignin-based products as well as the developments, opportunities, and challenges are highlighted.

Lignosulfonate-based bioactive coatings as soil improvers for lawns were developed using laccase as a biocatalyst. Incorporation of glycerol, xylitol and sorbitol as plasticizers considerably reduced the brittleness of the synthesized coatings of marine carbonate granules while thermal enzyme inactivation at 100 °C enabled the production of stable coatings. Heat inactivation produced stable coatings with a molecular weight of 2000 kDa and a viscosity of 4.5 × 10⁻³ Pas. The desired plasticity for the spray coating of soil improver granules was achieved by the addition of 2.7% of xylitol. Agriculture beneficial microorganisms (four different Bacillus species) were integrated into the coatings. The stable coatings protected the marine calcium carbonate granules, maintained the viability of the microorganisms and showed no toxic effects on the germination and growth of model plants including corn, wheat, salad, and tomato despite a slight delay in germination. Moreover, the coatings reduced the dust formation of soil improvers by 70%. CO₂ emission analysis showed potential for the reduction of up to 3.4 kg CO₂-eq. kg⁻¹ product, making it a viable alternative to fossil-based coatings.

Plants from the Nepenthes genus, which enumerates approximately 120 species, possess specialized pitchers enabling them to capture and digest various preys, mainly arthropods, from which the plants derive nutrients. The pitcher fluid contains many molecules of noteworthy importance, including antimicrobial compounds, traditionally used in medicine, as well as hydrolytic enzymes for prey digestion. In this study, polyesters films made from poly(ethylene terephthalate) (PET) and from poly(butylene adipate -co- terephthalate) (PBAT) were incubated in the pitcher of the carnivorous plants Nepenthes alata and Sarracenia purpurea. High performance liquid chromatography analysis revealed hydrolysis into their corresponding monomers, while hydrolysis efficiency was up to ten times higher in the presence of dried mealworm Tenebrio molitor and jasmonic acid. Proteomic analysis indicated the presence of the aspartic proteinase nepenthesin in most conditions, with high abundance in 70% of polyester-containing conditions compared to those without polyesters. Molecular docking simulations further suggested that nepenthesin has the potential to hydrolyze polyesters. While in contrast to cutinases there is only little information on hydrolysis of PET and PBAT by proteases in the literature, this work clearly demonstrates hydrolysis of both PET and PBAT by the recombinant protease nepenthesin, releasing similar amounts of TPA as the cutinase from Humicola insolens. These results suggest carnivorous plant fluids as a source for new enzymes for industrial applications such as for polyester hydrolysis.

Laccase-catalyzed repolymerization of technical lignins is an emerging biocatalytic strategy for upgrading lignin streams into polymeric systems and biomaterial precursors under mild reaction conditions. Lignosulfonates are attractive substrates for enzymatic polymerization due to their high water-solubility; however, their relatively low reactivity can limit their application. In contrast, organosolv lignin typically presents low-molecular weight and high phenolic content, which increase its susceptibility to laccase-mediated oxidation; however, its limited water solubility restricts enzymatic processing. In this work, lignin blending was evaluated as a strategy to modulate laccase-catalyzed polymerization by combining lignosulfonates (LS) with organosolv lignin from vine shoots (LVS). The effect of LVS incorporation on enzymatic oxidation was investigated through oxygen consumption measurements, viscosity evolution, molecular weight analysis and characterization of LS-based films. The presence of LVS modified oxidation kinetics, leading to prolonged oxidative activity, accelerated viscosity development and higher apparent molecular weight fractions at shorter reaction times compared to LS alone. LS-LVS films were produced to evaluate whether blending affected material surface properties. FTIR analysis supported structural changes consistent with oxidative coupling, while water contact angle measurements showed increased surface hydrophobicity in LS/LVS systems. Overall, the results demonstrate that blending lignins with different structural features can modulate enzymatic polymerization and influence the properties of LS films. This work highlights lignin blending as a simple biocatalytic strategy to modulate laccase-catalyzed polymerization and upgrade heterogeneous lignin streams toward lignin-based biomaterials within biorefinery concepts.