Thermophilic biocatalysts for one-step conversion of citrus waste into lactic acid.

Agri-food residues offer significant potential as a raw material for the production of L-lactic acid through microbial fermentation. Weizmannia coagulans, previously known as Bacillus coagulans, is a spore-forming, lactic acid-producing, gram-positive, with known probiotic and prebiotic properties. This study aimed to evaluate the feasibility of utilizing untreated citrus waste as a sustainable feedstock for the production of L-lactic acid in a one-step process, by using the strain W. coagulans MA-13. By employing a thermophilic enzymatic cocktail (Cellic CTec2) in conjunction with the hydrolytic capabilities of MA-13, biomass degradation was enhanced by up to 62%. Moreover, batch and fed-batch fermentation experiments demonstrated the complete fermentation of glucose into L-lactic acid, achieving a concentration of up to 44.8 g/L. These results point to MA-13 as a microbial cell factory for one-step production of L-lactic acid, by combining cost-effective saccharification with MA-13 fermentative performance, on agri-food wastes. Moreover, the potential of this approach for sustainable valorization of agricultural waste streams is successfully proven. KEY POINTS: • Valorization of citrus waste, an abundant residue in Mediterranean countries. • Sustainable production of the L-( +)-lactic acid in one-step process. • Enzymatic pretreatment is a valuable alternative to the use of chemical.

Pure titanium particle loaded nanocomposites: study on the polymer/filler interface and hMSC biocompatibility.

The integration of inorganic nanoparticles into polymer matrices allows for the modification of physical properties as well as the implementation of new features for unexplored application fields. Here, we propose the study of a new metal/polymer nanocomposite fabricated by dispersing pure Ti nanoparticles into a poly(methylmetacrilate) matrix via solvent casting process, to investigate its potential use as new biomaterial for biomedical applications. We demonstrated that Ti nanoparticles embedded in the poly(methylmetacrilate) matrix can act as reinforcing agent, not negatively influencing the biological response of human mesenchymal stem cell in terms of cytotoxicity and cell viability. As a function of relative amount and surface treatment, Ti nanoparticles may enhance mechanical strength of the composite-ranging from 31.1 ± 2.5 to 43.7 ± 0.7 MPa-also contributing to biological response in terms of adhesion and proliferation mechanisms. In particular, for 1 wt% Ti, treated Ti nanoparticles improve cell materials recognition, as confirmed by higher cell spreading-quantified in terms of cell area via image analysis-locally promoting stronger interactions at cell matrix interface. At this stage, these preliminary results suggest a promising use of pure Ti nanoparticles as filler in polymer composites for biomedical applications.

Unilateral NMR investigation of multifunctional treatments on stones based on colloidal inorganic and organic nanoparticles.

Consolidation and protection are among the most important treatments usually carried out in conservation of stone artifacts and monuments. In this paper, portable unilateral NMR and conventional techniques were used for investigating new multifunctional treatments based on tetraethoxysilane, silica, and polytetrafluoroethylene nanoparticles. The study was carried out on a very complex and heterogeneous porous stone such as tuff. NMR study allowed to obtain detailed information on the penetration depth of treatments, the hydrophobic effect, and changes in the open porosity caused by treatments. Physical and chemical inhomogeneities between the impregnated layers of tuff and the layers underneath were also detected. The average pores radius and pores interconnection obtained from NMR diffusion measurements were used for the first time to compare effects of different consolidating and/or protective treatments on stone. Because unilateral NMR technique is neither destructive nor invasive, investigation of treatments can be also carried out and optimized directly on buildings and monuments of interest for Cultural Heritage.

Artificial biomelanin: highly light-absorbing nano-sized eumelanin by biomimetic synthesis in chicken egg white.

The spontaneous oxidative polymerization of 0.01-1% w/w 5,6-dihydroxyindole (DHI) in chicken egg white (CEW) in the absence of added solvents leads to a black, water-soluble, and processable artificial biomelanin (ABM) with robust and 1 order of magnitude stronger broadband light absorption compared to natural and synthetic eumelanin suspensions. Small angle neutron scattering (SANS) and transmission electron microscopy (TEM) analysis indicated the presence in the ABM matrix of isolated eumelanin nanoparticles (≤100 nm) differing in shape from pure DHI melanin nanoparticles (SANS evidence). Electron paramagnetic resonance (EPR) spectra showed a slightly asymmetric signal (g ∼ 2.0035) similar to that of solid DHI melanin but with a smaller amplitude (ΔB), suggesting hindered spin delocalization in biomatrix. Enhanced light absorption, altered nanoparticle morphology and decreased free radical delocalization in ABM would reflect CEW-induced inhibition of eumelanin aggregation during polymerization accompanied in part by covalent binding of growing polymer to the proteins (SDS-PAGE evidence). The technological potential of eumelanin nanosizing by biomimetic synthesis within a CEW biomatrix is demonstrated by the preparation of an ABM-based black flexible film with characteristics comparable to those of commercially available polymers typically used in electronics and biomedical applications.

Exploring the Untapped Potential of Pine Nut Skin By-Products: A Holistic Characterization and Recycling Approach.

The increasing population, food demand, waste management concerns, and the search for sustainable alternatives to plastic polymers have led researchers to explore the potential of waste materials. This study focused on a waste of pine nut processing referred to in this paper as pine nut skin. For the first time, its nutritional profile, potential bioactive peptide, contaminants, and morphological structure were assessed. Pine nut skin was composed mainly of carbohydrates (56.2%) and fiber (27.5%). The fat (9.8%) was about 45%, 35%, and 20% saturated, monounsaturated, and polyunsaturated fatty acid, respectively, and Omega-9,-6, and -3 were detected. Notably, oleic acid, known for its health benefits, was found in significant quantities, resembling its presence in pine nut oil. The presence of bioactive compounds such as eicosapentaenoic acid (EPA) and phytosterols further adds to its nutritional value. Some essential elements were reported, whereas most of the contaminants such as heavy metals, polycyclic aromatic hydrocarbons, rare earth elements, and pesticides were below the limit of quantification. Furthermore, the in silico analysis showed the occurrence of potential precursor peptides of bioactive compounds, indicating health-promoting attributes. Lastly, the morphological structural characterization of the pine nut skin was followed by Fourier Transform Infrared and solid-state NMR spectroscopy to identify the major components, such as lignin, cellulose, and hemicellulose. The thermostability of the pine nut skin was monitored via thermogravimetric analysis, and the surface of the integument was analyzed via scanning electron microscopy and volumetric nitrogen adsorption. This information provides a more comprehensive view of the potential uses of pine nut skin as a filler material for biocomposite materials. A full characterization of the by-products of the food chain is essential for their more appropriate reuse.

Sustainable and Green Production of Nanostructured Cellulose by a 2-Step Mechano-Enzymatic Process.

Nanostructured cellulose (NC) represents an emerging sustainable biomaterial for diverse biotechnological applications; however, its production requires hazardous chemicals that render the process ecologically unfriendly. Using commercial plant-derived cellulose, an innovative strategy for NC production based on the combination of mechanical and enzymatic approaches was proposed as a sustainable alternative to conventional chemical procedures. After ball milling, the average length of the fibers was reduced by one order of magnitude (down to 10-20 µm) and the crystallinity index decreased from 0.54 to 0.07-0.18. Moreover, a 60 min ball milling pre-treatment followed by 3 h Cellic Ctec2 enzymatic hydrolysis led to NC production (15% yield). Analysis of the structural features of NC obtained by the mechano-enzymatic process revealed that the diameters of the obtained cellulose fibrils and particles were in the range of 200-500 nm and approximately 50 nm, respectively. Interestingly, the film-forming property on polyethylene (coating ≅ 2 µm thickness) was successfully demonstrated and a significant reduction (18%) of the oxygen transmission rate was obtained. Altogether, these findings demonstrated that nanostructured cellulose could be successfully produced using a novel, cheap, and rapid 2-step physico-enzymatic process that provides a potential green and sustainable route that could be exploitable in future biorefineries.

Poly(lactic acid)/Plasticizer/Nano-Silica Ternary Systems: Properties Evolution and Effects on Degradation Rate.

Plasticized nanocomposites based on poly(lactic acid) have been prepared by melt mixing following a two-step approach, adding two different oligomeric esters of lactic acid (OLAs) as plasticizers and fumed silica nanoparticles. The nanocomposites maintained a remarkable elongation at break in the presence of the nanoparticles, with no strong effects on modulus and strength. Measuring thermo-mechanical properties as a function of aging time revealed a progressive deterioration of properties, with the buildup of phase separation, related to the nature of the plasticizer. Materials containing hydroxyl-terminated OLA showed a higher stability of properties upon aging. On the contrary, a synergistic effect of the acid-terminated plasticizer and silica nanoparticles was pointed out, inducing an accelerated hydrolytic degradation of PLA: materials at high silica content exhibited a marked brittleness and a dramatic decrease of molecular weight after 16 weeks of aging.

Sustainable Cellulose-Aluminum-Plastic Composites from Beverage Cartons Scraps and Recycled Polyethylene.

The sustainable management of multilayer paper/plastic waste is a technological challenge due to its composite nature. In this paper, a mechanical recycling approach for multilayer cartons (MC) is reported, illustrating the realization of thermoplastic composites based on recycled polyethylene and an amount of milled MC ranging from 20 to 90 wt%. The effect of composition of the composites on the morphology and on thermal, mechanical, and water absorption behavior was investigated and rationalized, demonstrating that above 80 wt% of MC, the fibrous nature of the filler dominates the overall properties of the materials. A maleated polyethylene was also used as a coupling agent and its effectiveness in improving mechanical parameters of composites up to 60 wt% of MC was highlighted.

A versatile approach to evaluate the occurrence of microfibers in mussels Mytilus galloprovincialis.

Microplastics of fibrous shape are esteemed to be the most abundant micro-debris form present in the environment. Despite the occurrence of microfibers in fish may pose a risk to human health, the literature is scarce regarding studies on the contamination in commercial marine fish mostly due to methodological issues. In this study, a versatile approach, able to discriminate among natural and synthetic microfibers according to the evaluation of specific morphological features, is proposed in farmed mussels (Mytilus galloprovincialis). The approach was useful to determine that microfibers were present in 74% of mussel samples, with a mean number of 14.57 microfibers/individual, corresponding to 3.13 microfibers/g w.w. A negative correlation between the size of analysed mussels and the amount of microfibers/g w.w. was detected, showing that smaller specimens contained more microfibers than the larger ones. This work paves the way to further studies aimed to adequately assess the risk that microfibers may pose to marine biota, also considering the commercial value as seafood items of many species of the Mytilus genus and the potential implication for human exposure.

Development of nanocomposite based on hydroxyethylmethacrylate and functionalized fumed silica: mechanical, chemico-physical and biological characterization.

In this research work organic/inorganic nano composites were synthesized from poly-2-hydroxyethylmethacrylate and properly modified silica nanoparticles by in situ polymerization. In particular, fumed nanosilica was functionalized with methacryloylpropyltrimetoxy silane (MPTMS) in order to obtain a more homogeneous, reliable and mechanically performing nano composite. For comparison, nano composites with non functionalized silica were also prepared. Scanning electron microscopy was performed in order to visualize the effects of functionalization on the mode and state of dispersion. This analysis demonstrated that MPTMS grafted onto silica surface acts as an effective coupling agent and assures a good dispersion and distribution of nanoparticles as well as a strong nano particle/matrix interfacial adhesion. As a result of strong interactions occurring between phases, a pronounced increase of the glass transition temperature and mechanical parameters were recorded. Finally, these novel nano composites were seeded with murine fibroblast and human mesenchymal stem cells, and observed in time-lapse experiments proving an effective biological response.

Valorization and Mechanical Recycling of Heterogeneous Post-Consumer Polymer Waste through a Mechano-Chemical Process.

In this paper, a sustainable strategy to valorize and recycle heterogeneous polymer-based post-consumer waste is proposed. This strategy is based on a high-energy mechano-chemical treatment and has been applied to a polyolefin-rich fraction, coded as FIL/S, deriving from household plastic waste collection. This processing, performed in a planetary ball mill, allowed us to obtain fine grinding and, consequently, to induce an intimate mixing of the different polymer fractions and contaminants composing the FIL/S, as demonstrated by SEM analysis. As a result, an improvement in the deformability of the treated material was obtained, recording values for elongation at the break which were two and half times higher than the neat FIL/S. Finally, the addition of small amounts of organic peroxide during mechano-chemical treatment was tested, determining a more homogeneous morphology and a further improvement in mechanical parameters.

Comparison of biodegradable polyesters degradation behavior in sand.

Sandy beaches represent environmental compartments particularly vulnerable to litter pollution, and they reflect the magnitude of pollution of adjacent compartments: water and coastal areas. The substitution of conventional polymers by biodegradable materials is generally considered as an alternative for reducing environmental accumulation of plastic debris. The present study is aimed to investigate the degradation of poly(lactic acid), poly(ε-caprolactone), poly(butylenesuccinate adipate) and poly(3-hydroxybutyrate) buried in sand for 267 days, simulating them as beach litter. The analysed polyesters showed different degradation mechanisms and kinetics. PLA is mainly subjected to weathering by physical aging; after an initial faster degradation of the amorphous phase, PCL showed a decrease of its degradation rate; similarly to PCL, the degradation of PBSA started from the amorphous phase; PHB is clearly subjected to biological degradation. The degradation trend of the investigated materials in sand decreased in the order PHB > PBSA > PCL > PLA. PLA, PCL and PBSA did not undergo complete degradation in sand during the testing time.

Washing load influences the microplastic release from polyester fabrics by affecting wettability and mechanical stress.

Microplastics released from textiles during the washing process represent the most prevalent type of microparticles found in different environmental compartments and ecosystems around the world. Release of microfibres during the washing process of synthetic textiles is due to the mechanical and chemical stresses that clothes undergo in washing machines. Several washing process parameters, conditions, formulations of laundering additives have been correlated to microfibre release and some of them have been identified to affect microfibre release during washing process, while no correlation has been evaluated between microfibre release and washing load. In the present study, microfibre release was evaluated as function of the washing load in a real washing process, indicating a progressive decrease of microfibre release with increasing washing load. The quantity of released microfibres increased by around 5 times by decreasing the washing load due to a synergistic effect between water-volume to fabric ratio and mechanical stress during washing. Moreover, the higher mechanical stress to which the fabric is subjected in the case of a low washing load, hinders the discrimination of the effect on the release of other washing parameters like the type of detergent and laundry additives used.

Polyvinylpyrrolidone/Montmorillonite/Zinc Oxide Bionanosystems Prepared by Spray Drying.

In this study, microparticles of bionanomaterials were obtained by polyvinylpyrrolidone, montmoril-lonite, and zinc oxide bionanosystems produced through solution intercalation technique combined with a spray-drying process, aiming for possible application as drug delivery systems. The final microparticles obtained were evaluated in terms of their production yield, which varies between 39.2% and 56.9%. Thermal analysis showed no major changes in Tg of the nanocomposites, compared to the pure PVP polymer. Scanning electron microscopy analysis revealed a pseudo-spherical shape and confirmed the micrometric size of the microparticles. Transmission electron microscopy analysis corroborated the embedding of montmorillonite and ZnO within the polymer phase. Nuclear magnetic resonance and X-rays diffraction were used to study the nanoparticles dispersion, indicating a predominant intercalated morphology. This study suggests that the applied methodology is suitable for the high yields synthesis of nanocomposites PVP based microparticles with uniform size and shape, which can be promising for the production of a new drug delivery system.

Hyper-Crosslinked Polymer Nanocomposites Containing Mesoporous Silica Nanoparticles with Enhanced Adsorption Towards Polar Dyes.

The development of new styrene-based hyper-crosslinked nanocomposites (HCLN) containing mesoporous silica nanoparticles (MSN) is reported here as a new strategy to obtain functional high surface area materials with an enhanced hydrophilic character. The HCLN composition, morphology and porous structure were analyzed using a multi-technique approach. The HCLN displayed a high surface area (above 1600 m2/g) and higher microporosity than the corresponding hyper-crosslinked neat resin. The enhanced adsorption properties of the HCLN towards polar organic dyes was demonstrated through the adsorption of a reactive dye, Remazol Brilliant Blue R (RB). In particular, the HCLN containing 5phr MSN showed the highest adsorption capacity of RB.

Environmental life cycle assessment of the recycling processes of waste plastics recovered by landfill mining.

Enhanced Landfill Mining (ELFM) is a powerful tool for the sustainable management of landfill sites, aiming at both land reclamation and material recovery/reuse. To enhance the recovery and recycling rate of excavated plastic fractions, in most cases destined to energy recovery, new convenient, effective and sustainable strategies are needed. In this study, a recovery and valorization process of ELFM excavated plastics has been validated through an integrated experimental and Life Cycle Assessment (LCA) approach, demonstrating the environmental sustainability of the secondary raw material generated, in terms of use of resources and emissions generated. In particular, the secondary granulate from ELFM was compared with a virgin product and the last one resulted to have a higher impact (more than 4.46 times greater than the first one), in particular for the use of the resource crude oil as raw material in the production of primary LDPE. The valorization process of the excavated plastic made the mechanical properties of the secondary raw material comparable to that of a primary material.

Recycling Polyethylene-Rich Plastic Waste from Landfill Reclamation: Toward an Enhanced Landfill-Mining Approach.

In the frame of a circular economy, the maximization of secondary raw-material recovery is necessary to increase the economic and environmental sustainability of landfill mining and reclamation activities. In this paper, the polyethylene-rich plastic fraction recovered from the reclamation of an abandoned industrial landfill (landfill-recovered plastic, LRP) has been characterized through spectroscopic, thermal, morphological, and mechanical analyses. Then, an economically viable valorization and recycling strategy was set up. The effectiveness of this strategy in the enhancement of LRP properties has been demonstrated through morphological and mechanical characterizations.

Hexamethylenediamine-Mediated Polydopamine Film Deposition: Inhibition by Resorcinol as a Strategy for Mapping Quinone Targeting Mechanisms.

Hexamethylenediamine (HMDA) and other long chain aliphatic diamines can induce substrate-independent polymer film deposition from dopamine and several other catechols substrates at relatively low concentrations, however the mechanism of the diamine-promoted effect has remained little understood. Herein, we report data indicating that: (a) film deposition from 1 mM HMDA and dopamine is not affected by chemical oxidation with periodate but is markedly inhibited by resorcinol, which also prevents PDA film formation at 10 mM monomer concentration in the absence of HMDA; (b) N-acetylation of HMDA completely inhibits the effect on PDA film formation; (c) HMDA enables surface functionalization with 1 mM 5,6-dihydroxyindole (DHI) polymerization at pH 9.0 in a resorcinol-inhibitable manner. Structural investigation of the polymers produced from dopamine and DHI in the presence of HMDA using solid state 13C and 15N NMR and MALDI-MS suggested formation of covalent cross linked structures. It is concluded that HMDA enhances polydopamine adhesion by acting both on dopamine quinone and downstream, e.g., via covalent coupling with DHI. These results provide new insights into the mechanisms of PDA adhesion and disclose resorcinol as a new potent tool for targeting/mapping quinone intermediates and for controlling polymer growth.

Critical Factors for the Recycling of Different End-of-Life Materials: Wood Wastes, Automotive Shredded Residues, and Dismantled Wind Turbine Blades.

Different classes of wastes, namely wooden wastes, plastic fractions from automotive shredded residues, and glass fiber reinforced composite wastes obtained from dismantled wind turbines blades were analyzed in view of their possible recycling. Wooden wastes included municipal bulky wastes, construction and demolition wastes, and furniture wastes. The applied characterization protocol, based on Fourier transform infrared (FTIR) spectroscopy in attenuated total reflection (ATR) mode, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX), and thermogravimetric analysis (TG) coupled with FTIR spectrometry for the investigation of the evolved gases, revealed that the selected classes of wastes are very complex and heterogeneous materials, containing different impurities that can represent serious obstacles toward their reuse/recycling. Critical parameters were analyzed and discussed, and recommendations were reported for a safe and sustainable recycling of these classes of materials.

Effect of Microfibrillated Cellulose on Microstructure and Properties of Poly(vinyl alcohol) Foams.

Poly(vinyl alcohol) foams, containing different amounts of microfibrillated cellulose, were prepared through an eco-friendly procedure based on high-speed mixing and freeze-drying. The effect of filler amount on cell shape and regularity was studied by scanning electron microscopy (SEM) and the evolution of the microstructure was assessed through dynamic cryo-SEM. Fourier Transformed Infrared Analysis and Differential Scanning Calorimetry measurements revealed the presence of hydrogen bond interaction among cellulosic filler and the matrix. The modulus and compression deflection of neat PVA were significantly improved by increasing the amount of microfibrillated cellulose content with respect to foams realised with pulp cellulose fibers.