Sequential bioprocessing of Ulva rigida to produce lignocellulolytic enzymes and to improve its nutritional value as aquaculture feed

The macroalgae aquaculture industry has grown up in the last years, and new applications for macroalgae should be considered. In this work, sequential biological treatments as solid-state fermentation (SSF) by Aspergillus ibericus and enzymatic hydrolysis (EH) were applied to washed and unwashed Ulva rigida. SSF of unwashed macroalgae showed higher xylanase (359.8 U/g), cellulase (73.07 U/g) and β-glucosidase (14.9 U/g) activities per dry mass of macroalgae. After SSF, two strategies to carry out EH were assayed. The best process was SSF followed by EH by simply adding a buffer. The non-starch polysaccharides content was reduced by 93.2 %, achieving a glucan conversion of 98 %. In addition, the antioxidant activity was improved 2.8-fold and the protein concentration of macroalgae extracts increased from 16.9 % to 29.8 % (w/w). These biological treatments allowed to increase macroalgae value as feedstuff with potential for use in aquafeeds.
Helena Fernandes was supported by PhD grant SFRH/BD/131219/ 2017, funded by the Portuguese Foundation for Science and Technology (FCT). José Manuel Salgado was supported by grant CEB/N2020 – INV/01/ 2016 from Project “BIOTECNORTE - Underpinning Biotechnology to foster the north of Portugal bioeconomy” (NORTE-01-0145-FEDER000004). This work was supported by the R&D&I project “Development of innovative sustainable protein and omega-3 rich feedstuffs for aquafeeds, from local agro-industrial by-products”, reference POCI-01- 0145-FEDER-030377, funded by European Regional Development Fund (ERDF) and Portuguese Foundation for Science and Technology (FCT); by the InovFeed project (ref. MAR-02.01.01-FEAMP-0111) supported by Programa Operacional Mar2020, and by the Portuguese Foundation for Science and Technology under the scope of the strategic funding of UID/BIO/04469/2019 and BioTec-Norte operation (NORTE-01-0145- FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte.
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