Browsing by Subject "Microalgae hydrolysis"

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    Effects of raw and hydrolysed Nannochloropsis gaditana biomass included at low level in finishing diets for gilthead seabream (Sparus aurata) on fillet quality and shelf life
    (Springer, 2023-06) Sáez, Mª Isabel; Galafat, Alba; Suárez, Mª Dolores; Chaves Pozo, Elena; Arizcun, Marta; Ayala Florenciano, María Dolores; Alarcón, Francisco Javier; Martínez, Tomás F.; Anatomía y Anatomía Patológica Comparada
    Numerous studies evaluating the effects of the incorporation of microalgae in feeds have reported favourable impacts on different physiological aspects of aquacultured fish. Although productivity is the major goal in terms of profitability in fish farming, qualitative aspects are gaining the attention of producers, given the relevance of quality attributes related to organoleptic parameters, proximal composition, and shelf life on the commercial value of fish. Indeed, microalgae are acknowledged for their richness in substances with potential positive effects on all those quality attributes. In this context, this study assesses the effects of finishing diets enriched with the microalga Nannochloropsis gaditana, either crude or enzymatically hydrolysed, on several quality parameters of gilthead seabream (Sparus aurata) fillets. Two inclusion levels (2.5 and 5%) of raw and enzymatically hydrolysed microalgal biomass were incorporated into diets, plus a microalgae-free control diet, and a 42-day feeding trial was carried out on fish of commercial size (approx. 500 g body weight). The influence of the experimental diets on fish biometry, fillet quality parameters, and shelf life was evaluated. The results indicate, overall, that microalgae-enriched diets yielded favourable, dose-dependent effects on several objective quality parameters of fillets, namely, improved fatty acid profile, reduced microbial counts, enhanced lipid oxidative status, and improved textural and skin colour attributes. Although the enzymatic pre-treatment of the microalgal biomass was expected to impact positively its functional effects on all quality parameters, however, no general trend was observed
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    Evaluation of Nannochloropsis gaditana raw and hydrolysed biomass at low inclusion level as dietary functional additive for gilthead seabream (Sparus aurata) juveniles
    (Elsevier, 2022-04-28) Sáez, María Isabel; Galafat, Alba; Vizcaíno, Antonio Jesús; Chaves-Pozo, Elena; Ayala Florenciano, María Dolores; Arizcun, Marta; Alarcón, Francisco Javier; Suárez, María Dolores; Martínez, Tomás Francisco; Anatomía y Anatomía Patológica Comparada
    Abundant research is being carried out in the last years aimed at exploring microalgal biomass as nutrient source for different species of aquacultured fish. Some microalgae species, such as Nannochloropsis gaditana, have thick cell walls rich in cellulose, which might well reduce the bioavailability of intracellular active compounds. Among the alternatives aimed at overcoming this limitation, cellulase enzyme hydrolysis is proposed as a convenient and practical solution. In this regard, an in vitro assay was carried out, in which N. gaditana biomass was treated with cellulase (5% w/w basis) and the release of soluble compounds (reducing sugars, free amino acids and total phenolics) into the reaction medium was measured and compared to untreated raw biomass. The results confirmed increased yields of those compounds as a result of the enzyme pre-treatment. A 90-d feeding trial was also carried out in order to assess in vivo the influence of the inclusion of N. gaditana in feeds on juvenile gilthead seabream (Sparus aurata) growth, digestive physiology and body composition. Microalgal biomass was added at two inclusion levels (25 and 50 g kg 1 dry weight) in four experimental feeds, either crude or enzymatically pretreated. Animals (15.1 g initial body weight) were randomly assigned to five dietary treatments (two inclusion levels, 2.5 and 5%, and two microalgae formats, raw and enzymatically hydrolysed, plus a microalgae-free control), and distributed triplicate tanks per dietary treatment. Fish were withdrawn after 45 and 90 days, and proximate composition, muscle fatty acid and amino acid profiles, muscle and liver lipid oxidation, instrumental skin colour, digestive enzyme activities, as well as structural and ultrastructural changes in the intestinal mucosa were determined. No differences attributable to the dietary treatments were found with regard to fish growth or proximate composition at the end of the feeding trial. On the contrary, the inclusion of microalgal biomass, irrespectively of the cellulase pre-treatment, caused beneficial effects on some physiological parameters (namely digestive mucosa structure and functionality, oxidative status of muscle lipids, and instrumental colour). The only clear improvement found in fish attributable to the cellulase pre-treatment of the microalgal biomass was related to the prevention of muscle lipid oxidation. Overall, the results suggest that N. gaditana used as additive (at inclusion level below 5%) in feeds might represent a valuable nutritional strategy for S. aurata juveniles, even if growth was not affected.