Microplastics pollution is one of the main environmental challenges of our time, even though microplastics were observed for the first time almost 50 years ago. Microplastics—little plastic fragments smaller than 5 mm in size—are released from bigger plastic objects during their use, maintenance, or disposal. As their release is uncontrolled and mostly uncontrollable, microplastics end up in the environment and are easily transported across the world, polluting nearly every ecosystem, especially the aquatic ones. Hence, microplastics represent a huge menace for many living species: they are ingested unintentionally by smaller animals and transferred along the food chain up to human beings, even threatening our health. It is therefore vital to take action against microplastics and many technologies have been designed in recent years with this purpose in mind. This paper provides an overview of the main solutions developed thus far to reduce further microplastic emissions and to collect those already released.

Apples are among the most commonly cultivated fruits globally. Approximately 65% of annual apple production is transformed into apple juice concentrate generating a large amount of waste material named apple pomace, which includes seeds, skin, and other components. Disposing of apple by-products directly into the environment constitutes a source of environmental pollution due to its high-water content and easily fermentable nature. Apple pomace is rich in polyphenols that can be utilized as active components in cosmetic, nutraceutical, or pharmaceutical products. The present study aims to describe and compare different physical methods for the extraction of polyphenols from apple pomace. Water was used as the extraction solvent in thermal-stirred extraction (TSE), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE). The best extraction conditions were identified in terms of solid to solvent ratio, temperature, power, and time through a kinetic study. The best extraction parameters were compared environmentally on a pilot scale through a life cycle assessment (LCA). All the results demonstrated the MAE is the best technique to extract polyphenol from apple pomace in terms yield and environmental impact proving that it is possible to transform waste into a sustainable source of bioactive ingredients.

Tomatoes are rich in carotenoids, which remain in significant quantities in tomato pomace and can be sustainably extracted. This study aimed to develop a method for extracting carotenoids from tomato pomace using deep eutectic solvents composed of menthol and fatty acids (butyric, hexanoic, caprylic, lauric, and palmitic), as an alternative to toxic and polluting organic solvents. Preliminary screening identified the most effective deep eutectic solvent, while design of experiment and a kinetic study optimized the extraction process. Under optimal conditions, the DES extracted approximately 300 μg/g of carotenoids on a dry weight basis. HPLC analysis of the extract quantified 24 μg/g ± 5 of β-carotene and 52 μg/g ± 2 of lycopene. The menthol-butyric acid DES outperformed conventional organic solvents, emphasizing its sustainability and efficiency.

After rice harvesting, the milling processes generate many by-products including husk, bran, germs, and broken rice representing around 40% of the total grain. Bran, one of the external cereal layers, contains proteins, dietary fibers, minerals, and lipids. One of the most common rice bran utilization is the extraction of rice bran oil (RBO). Among all vegetable oils, RBO presents a unique chemical composition rich in antioxidant compounds such as γ-oryzanol that provide several beneficial properties. RBO is generally extracted by exploiting hexane, a solvent toxic to the environment and human health. The growing demand for this oil has led researchers to look for more sustainable extraction techniques. Supercritical carbon dioxide (SC-CO₂) has been successfully applied to extract oil and functional compounds from several matrices. In this work, the SC-CO₂ extraction of RBO was optimized using a Design of Experiment (DoE) on a pilot scale. "The DoE approach involving multilinear regression allowed modelling the yield in RBO and gamma oryzanol as a function of temperature and pressure, keeping the extraction time constant, as decided by the company. This approach made it possible to optimize the extraction yield and to identify the best temperature (40 °C), while also highlighting that pressure did not play any influential role in the process, at least concerning the analyzed experimental domain on this industrial plant. A model for computing the extraction yield as a function of temperature and pressure was obtained. This study shows that it is possible to obtain good quality RBO, rich in γ-oryzanol and essential fatty acids, using low temperatures and pressures, starting from a rice milling by-product. Graphical Abstract

To successfully scale-up the production of bio-based building blocks through CO₂ and H₂-based gas fermentation, it is crucial to deeply understand and control the microbial catalyst response to the bioreactor environment. This study investigates the effects of key process parameters, such as CO₂ and H₂ partial pressures, gas feeding strategies, and mixture composition, on the production pathways of an evolved Clostridium carboxidivorans strain. The ultimate goal is to optimize 1-hexanol production in elevated-pressure stirred-tank reactors. Continuous gas feeding enhanced acetogenic and solventogenic metabolisms, while gas-limited conditions promoted chain elongation to caproic acid. An optimized process, combining an initial gas-limited step followed by a continuous gas phase, increased 1-hexanol production, achieving a maximum biomass-specific productivity of 0.9 g g_CDW^-1 day^-1. In-situ product extraction improved 1-hexanol carbon selectivity to an unprecedented 60 %. These findings demonstrate the potential of CO₂ and H₂-fed fermentation to produce high-value chemicals other than ethanol and acetate.