Silk is a natural composite fiber composed mainly of hydrophobic fibroin and hydrophilic sericin, produced by the silkworm Bombyx mori. In the textile industry, the cocoons of B. mori are processed into silk fabric, where the sericin is substantially removed and usually discarded in wastewater. This wastewater pollutes the environment and water sources. However, sericin has been recognized as a potential biomaterial due to its biocompatibility, immunocompatibility, biodegradability, anti-inflammatory, antibacterial, antioxidant and photoprotective properties. Moreover, sericin can produce hydrogels, films, sponges, foams, dressings, particles, fibers, etc., for various biomedical and pharmaceutical applications (e.g., tissue engineering, wound healing, drug delivery, cosmetics). Given the severe environmental pollution caused by the disposal of sericin and its beneficial properties, there has been growing interest in upcycling this biomaterial, which could have a strong and positive economic, social and environmental impact.

Sericin has been characterized as demonstrating a variety of bioactivities, establishing it as a valuable resource for biomedical and pharmaceutical applications. The diverse biological activities of sericin are likely linked to its unique biochemical composition and properties. This study aimed to assess the effect of origin, seasonality, and amino acid composition on the bioactivity of sericin samples from two Portuguese regions compared to commercial sericin. The amino acid profile was analyzed using HPLC-FLD. Moreover, several bioactivities were assessed through in vitro assays, including antiproliferative effects, cell migration, antimicrobial activity, anticoagulant properties, antioxidant capacity, and anti-inflammatory effects. The results obtained in this work revealed that the origin and season affect the sericin amino acid profile. In its pure state, sericin exhibited a low content of free amino acids, with tyrosine being the most abundant (53.42–84.99%). In contrast, hydrolyzed sericin displayed a higher amino acid content dominated by serine (54.05–59.48%). Regarding bioactivities, the sericin tested did not demonstrate antioxidant or anti-inflammatory potential in the conducted tests. Notwithstanding, it showed antiproliferative activity in contact with human tumor cell lines at a minimum concentration of 0.52 mg/mL. Regarding antimicrobial activity, sericin had the capacity to inhibit the growth of the bacteria and fungi tested at concentrations between 5 and 10 mg/mL. Additionally, sericin demonstrated its capacity to prolong the coagulation time in pooled human plasma, indicating a potential anticoagulant activity. In addition, the origin and season also revealed their impact on biological activities, and sericin collected in Bragança in 2021 (S3) and 2022 (S4) demonstrated higher antiproliferative, antibacterial, and anticoagulant potentials. Future studies should focus on optimizing sericin’s bioactivities and elucidating its molecular mechanisms for clinical and therapeutic applications.

Chestnut brown rot caused by Gnomoniopsis smithogilvyi represents an increasing threat to Castanea sativa production, although its endophytic behaviour and response to pre-harvest management strategies under field conditions remain poorly understood. This study evaluated the occurrence of G. smithogilvyi in different chestnut tissues and assessed the effects of targeted field treatments on pathogen colonisation and fruit quality in commercial orchards located in north-eastern Portugal. Field trials included applications of a biological fungicide (Problad^®), an inorganic micronutrient fertilizer (Fungicrops Bio^®), a sulfur-micronutrient fertilizer (KSC Mix^®), and a potassium-phosphonate chemical fungicide (Fosetyl-Al^®), alongside untreated control orchards. Samples of leaves, branches, burrs, and nuts were subjected to microbiological and molecular analyses, while fruit external quality parameters were also assessed. G. smithogilvyi was detected in all analysed organs, confirming its widespread endophytic occurrence. Treatment effects were more pronounced in reproductive tissues, with Problad^® and Fosetyl-Al^® significantly reducing pathogen incidence in burrs and nuts compared with the control. KSC Mix^® promoted fruit development but did not significantly reduce fungal incidence. Treated orchards generally showed improved fruit quality and lower insect infestation. Phylogenetic analysis confirmed the identity of all isolates as G. smithogilvyi. Overall, the results highlight the complexity of managing chestnut brown rot and support the need for integrated and sustainable disease management strategies.