Chitin was extracted from Polybius henslowii, a swimming crab, captured in large quantities throughout the Portuguese coast by purse seine vessels as bycatch. After standard chitin extraction procedures, water-soluble chitosan products were obtained via two different methods: (1) N-acetylation with the addition of acetic anhydride and (2) a reaction with hydrogen peroxide. The chemical structure and molecular weight of chitosan derivatives, water-soluble chitosan (WSC) and chitooligosaccharides (COS), were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and gel permeation chromatography (GPC). Antioxidant and metal chelation activities were evaluated, and the growth inhibition capacity was tested on four phytopatogens. The chitooligosaccharides from pereopods (pCOS) and shell body parts (sCOS) inhibited all fungal species tested, particularly Cryphonectria parasitica with 84.7% and 85.5%, respectively. Both radical scavenging and antifungal activities proved to be dose-dependent. Chitooligosaccharides with a low molecular weight (2.7, 7.4, and 10.4 Kg·mol⁻¹) showed the highest activity among all properties tested. These results suggested that chitosan derivatives from P. henslowii raw material could potentially be used against phytopathogens or as ingredient in cosmetics and other products related to oxidative stress.

The four plants pathogens, Botrytis cinerea, Phytophthora cinnamomi, Cryphonectria parasitica and Heterobasidion annosum are responsible for several diseases affecting different plant species in Portugal, such as pines (H. annosum), chestnuts (P. cinnamomi and C. parasitica) and eucalyptus (B. cinerea). These pathogens incurs in large economic losses, and ultimately causes the death of these plants. The use of biopolymers as antimicrobial agents, such as chitosan (derived from chitin), is increasing, in order to reduce the negative impact of conventional chemical treatments on the environment, avoiding health risks. Therefore, eco-friendly polymers were produced through (1) N-acetylation with addition of acetic anhydride and (2) hydrogen peroxide of chitosan samples, obtained from two different sources: shrimp (commercial chitosan) and swimming crab bycatch specie Polybius henslowii. The chemical structure and molecular weight of the prepared chitosan derivatives, water soluble chitosan (WSC) and chitooligosaccharides (COS), was confirmed by Fourier Transform Infrared (FT-IR) and Gel Permeation Chromatography (GPC) and their antifungal activity evaluated against Botrytis cinerea, Phytophthora cinnamomi, Cryphonectria parasitica and Heterobasidion annosum. The concentration range varied from 0.0125 to 0.1 mg/mL and inhibition percentages were determined by differences in radial growth on the agar plates for all species. Although not all species tested exhibited equal vulnerability towards the concentrations range, antifungal activity of chitosan samples proved to be dependent, increasing the inhibitory capacity with lower concentrations. The results obtained support the use of chitosan fromPolybius henslowii when compared with commercial chitosan with shrimp towards antifungal approaches, suggesting that chitin producers can rely on this crab waste as a raw material for chitin extraction, adding value to this bycatch specie. Financial support was obtained from European Fisheries Fund – Axis 4 managed by Fishery Local Action Group Oeste-Portugal.

The world´s growing food demand poses as a major concern on agriculture resources. In order to meet the demand resulting from demographic studies, it is extremely important to improve the production technologies in order to achieve high agricultural productivity. Proper fertilization and efficient pests control in cultures are required to obtain a high quality production. In order to improve crop resistance against temperature fluctuations and diseases, several strategies have been tested, such as seed coating (Omolehin et al., 2005). Although current practices effectively enhance germination and reduce losses, the conventional seed coating agents are not the best alternative, since it relies on chemical fertilizers and pesticides addition to the soil, leading to environmental costs. In addition, pests may develop resistance against them, which implies the use of increasingly larger amounts to be efficient (Altieri and Nicholls, 2003). Therefore, there is an increasing demand for safer and more eco-friendly alternatives. Chitosan is a cationic polysaccharide produced by the alkaline N-deacetylation of chitin. The positive charge of chitosan confers numerous and unique physiological and biological properties with great potential in a wide range of industries, such as water treatment, food processing, medicine and pharmacology (Rinaudo, 2004). Furthermore, chitosan have been recognized as a product to enhance crop production due to its bioactivities: biodegradability, growth stimulation and seed germination, increasing nutrient uptake, reducing oxidative stress, increasing in chlorophyll content, photosynthetic and chloroplast enlargement in the leaves, antifungal, antiviral and antibacterial properties (Hadrami et al., 2010; Hadwiger, 2004). Therefore, it can be used as foliar spraying, seed coating, seedling root dipping; soil enrichment or as supplement into plant tissue media (Pichyangkura, R., Chadchawan, 2015). In this context, our aim was to study the effects of chitosan, extracted from marine resources, on biophysical characteristics commonly farmed tomato and coriander species, Solanum lycopersicum and Coriandrum sativum, respectively. For that we have used medium and lower molecular weight chitosan with and without acetic acid and ascorbic acid. The crops were all treated at the same conditions, in a greenhouse with controlled temperature (T=24ºC), aeration and photoperiod (12h:12h light:dark). Preliminary results showed for both species an enhancing of germination rates of seeds soaked with chitosan when compared to control seeds (without chitosan). Furthermore, growth measurements also showed differences between chitosan treatments and remaining conditions.