PROALGAE - Probióticos do microbiota intestinal de peixes: uma ferramenta para melhorar a utilização de macroalgas e a saúde dos peixes

The advantages of seaweed (SW) extracts in improving fish anti-inflammatory, anti-oxidant, and immune mechanisms (FCT project PTDC/CVT-WEL/5207/2014 of which P.ENES was PI), and in contrast, the failure of dietary whole-SW and the mechanical treatments used in improving SW digestibility, nutrients and active compounds bioavailability (INTERREG Spain-Portugal project of which P.ENES was core team member), trigger P.ENES to address PROALGAE major scientific question: Can autochthonous-selected probiotic (PRO) improve the use of SW, thus supporting a sustainable and cost-effective fish growth without compromising fish health and welfare? Novel PRO sporeforming bacteria isolated from European sea bass (ESB) gut microbiota and screened for their ability to digest cell wall water-soluble polysaccharides (CWPS) of SW will be the strategy used within this goal. PRO effectiveness of selected bacteria will be evaluated for their potential to improve SW utilization, fish growth performance, and health. Overall, PROALGAE aims to contribute to the development of cost-effective and eco-friendly diets, aiming at improving aquaculture sustainability. To address PROALGAE scientific question, the project will fulfil the following 6 specific objectives: i) Assess the impact of SW-enriched diets on gut microbiota Taking advantage of P.ENES international patented technology (PCT/IB2019/059131), and the promising PRO solutions obtained by P.ENES to digest plant feedstuffs (PI of the FCT project EXPL/MAR-BIO/0351/2013) and insect meal (PI of the FCT project 2022.02618.PTDC), a selective pressure through dietary modulation (SW-based diets) on fish gut microbiota will be applied aiming to obtain an enrichment of bacteria with a secretome able to utilize SW CWPS. ii) Isolate and identify gut sporeforming bacteria able to hydrolyze CWPS Using an in vitro functional screening approach (the ability to utilize CWPS) and a selection oriented for a specific group (sporeformers), PROALGAE aim to obtain fish gut bacteria that fulfill EFSA safety requirements to be eligible as PRO. iii) Evaluate PRO interaction with gut cells An in vitro approach using fish gut epithelial cell lines and primary cell cultures of lymphocytes will be performed aiming to further screen PRO according to their cytotoxity, mode of interference with bacterial pathogens, and immunomodulatory effects on gastrointestinal mucosal immunity. iv) Assess PRO enhancement of fish’s CWPS utilization, digestive function, and growth Using an in vivo approach, PRO will be further screened according to CWPS digestibility improvement. The most promising CWPS-hydrolysing PRO will be thereafter evaluated regarding fish’s zootechnic performance. v) Evaluate PRO capability to improve fish immunological status and disease resistance Since the use of PRO as immunostimulants is considered a promising strategy for the control of fish pathogens, PROALGAE aims to in vivo assess PRO effects on improving ESB immune response and disease resistance. vi) Assess PRO capability of modulating gut microbiota communities and gut-health Verify the potential of PRO to colonize fish gut and impact bacterial diversity and its effects in ESB gut health, namely in minimizing possible inflammatory effects of SW-based diets.