De Martino, Ester (2025) Enzymatic biotechnologies to recover by-products from agrifood waste. [Tesi di dottorato]

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Abstract

Agriculture is estimated to generate about 700 million tons of waste annually in the European Union (EU). The “agri-food system” definition covers the journey of food from tillage to table – from when it is planted, grown, harvested, processed, packaged, transported, distributed, traded, bought, prepared, eaten and disposed of. It also encompasses non-food products such as forestry, animal rearing, use of feedstock, biomass to produce biofuels and fibres, and it constitutes all of the activities, investments and choices made. What comes from food production, is known as "agri-food waste". Waste refers to unwanted materials that hold no value, often seen as unusable and requiring disposal, thereby affecting both economic and ecological systems. Hazelnut (Corylus avellana, L.) is the fifth most produced tree nut in the world: Italy ranks second with 15% of the total production and 11% of the total exports. Different residues originate from the hazelnut industry during the harvesting and post-harvesting processes, among them there are hazelnut skins (HS). HS is the perisperm of the hazelnut kernel, which represents approximately 2.5% of the kernel weight. The attention through HS is due to the presence of interesting molecules that could be still valorised, mainly polyphenols and polysaccharides. Industrial Hemp (Cannabis sativa, L.) is one of the most cultivated and used industrial crops worldwide. From 2018 data in Europe, France leads the production accounting for 37% of total production, followed by Italy and the Netherlands which account both for 8%. Hemp is cultivated for many industrial purposes and hemp supply chain derives an interesting byproduct, the shive, which is obtained from decortication of fiber. The attention to hemp shives is due to the presence of interesting molecules that could be still valorised; also in this case, they are mainly polysaccharides. These residues may be defined as “lignocellulosic biomass” which is referred to an abundant source of carbon-based renewable material, consisting of mainly cellulose, hemicellulose, and lignin, and to a lesser amount, also of pectin, proteins, and minerals. These connecting structures, often termed lignin–carbohydrate complexes, consist of a cellulose skeleton, made up of cellulose fibrils, which is embedded in a hemicellulose–lignin matrix. The large variation in composition and substitution pattern of lignocellulosic polymers results in the formation of various co-polymeric substructures upon their interaction with cellulose and contribute to lignocellulose recalcitrance. To valorise local lignocellulosic biomass resources, enzyme technology represents an important tool which perfectly meets circular economy criteria. Enzymes are proteins with powerful catalytic activity whom application is highly efficient considering enzymatic specificity, their ability to operate under varying pH, temperature, and pressure conditions. In order to disassemble the matrices in object, several carbohydrolases have been tested and then the effect they induced was evaluated both on insoluble and soluble fractions. According to the obtained results, it can be stated that enzymatic approach is useful to disassemble lignocellulosic matrices and obtained molecules can be still used in new food, feed and general formulations.

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