Microbiota composition and intestinal integrity remain unaltered after the inclusion of hydrolysed Nannochloropsis gaditana in Sparus aurata diet

Abstract

The use of lysed microalgae in the diet of carnivorous fish can increase the bioavailability of proteins and bioactive compounds, such as unsaturated fatty acids or vitamins in the digestive tract. These are essential molecules for the proper physiological development of fish in aquaculture. However, some antinutritional components and other undesirable molecules can be released from an excess of microalgae supplied, compromising the integrity of the intestine. The inclusion of small amounts of hydrolized microalgae in the fish diet can be a good strategy to avoid negative effects, improving the availability of beneficial compounds. Nannochloropsis gaditana is an interesting microalgae as it contains nutraceuticals. Previous studies reported beneficial effects after its inclusion in the diet of Sparus aurata, a widely cultured species in Europe and in all Mediterranean countries. However, administration of raw microalgae can produce intestinal inflammation, increased intestinal permeability, bacterial translocation and disturbance of digestion and absorption processes. The aim of this study was to evaluate changes in the intestinal microbiota and barrier stability of S. aurata fed with low inclusion (5%) hydrolysed N. gaditana. Intestinal microbiota was analyzed using Illumina MiSeq technology and libraries were constructed using variable regions V3–V4 of 16S rDNA molecules. Analysis were based in the identification, quantification and comparison of sequences. The predictive intestinal microbial functionality was analyzed with PICRUSt software. The results determined that the intestinal microbiota bacterial composition and the predictive intestinal microbiota functionality did not change statistically after the inclusion of N. gaditana on the diet. The study of gene expression showed that genes involved in intestinal permeability and integrity were not altered in fish treated with the experimental diet. The potential functionality and bacterial taxonomic composition of the intestinal microbiota, and the expression of integrity and permeability genes in the intestine of the carnivorous fish S. aurata were not affected by the inclusion of hydrolysed 5% N. gaditana microalgae.

The effect of dietary fish oil replacement by microalgae on the gilthead sea bream midgut bacterial microbiota

“…In our results the diet containing M. gaditana (MI) showed a decrease in the values of all alpha diversity indices, compared to the control (FO), but not statistically significant. Cerezo-Ortega et al (2021) also reported no statistically significant differences in microbial diversity indices (alpha and beta diversity) in Sparus aurata gut after the inclusion of 5% hydrolysed M. gaditana .…”

“…However, the above combination along with dietary inulin and the utilization of its b-glycans, has demonstrated immunostimulant effects, influencing intestinal gene expression (Cerezuela et al 2013; Reis et al 2021; Teixeira et al 2022). The use of M. gaditana showed that gut microbiota composition and intestinal integrity remained unaltered (Cerezo-Ortega et al 2021) or an increase in intestinal microbiota richness without affecting intestinal morphology and function (Jorge et al 2019). When used in combination with other species ( Chlorella sp., Arthrospira sp., Tisochrysis lutea , Scenedesmus almeriensis ) it was shown to favour the presence of probiotic bacteria in the gut and reduce the presence of pathogenic species (Garcia-Márquez et al 2023; Garcia-Márquez et al 2023).…”

Dietary Application of the Microalga Lobosphaera incisa P127 Reduces Severity of Intestinal Inflammation, Modulates Gut‐Associated Gene Expression, and Microbiome in the Zebrafish Model of IBD

“…There is a growing number of reports that indicate the effects of microalgae consumption on gut microbiome with no adverse or positive effects on intestinal health in fish, [41,92] human trials, or animal models. [19] In our study, the microbiome composition was altered in fish receiving diets supplemented with Ns nutrient-replete L. incisa P127; the increase in Cetobacteria paralleled the increase in the inclusion level.…”

Microalgae with immunomodulatory effects on fish

“…89,90 In a first effort to explore the immunostimulatory activity of N. gaditana, Cerezuela the weight and length of S. aurata 91 ; however, its dietary inclusion did not affect parameters of the intestinal health and digestive capacity of S. aurata, but could modulate intestinal microbiota. 65,92 Recently, the ability of the genus Nannochloropsis to reduce the effects of different types of stress related to aquaculture has been explored. On the one hand, Monteiro et al 93 showed that Tackle Meagre (Argyrosomus regius) supplemented with N. gaditana at 1% and subjected to acute handling stress had lower gene expression of proinflammatory cytokines tnf-α and il-1β genes, as well as a lower number of parameters related to oxidative stress.…”

“…Additionally, the expression of the β‐defensin ( bdef ) gene in HK leukocytes upregulated in the highest dose of microalgae at Week 4. Subsequent trials showed that the supplementation of N. gaditana at various concentrations improved the weight and length of S. aurata 91 ; however, its dietary inclusion did not affect parameters of the intestinal health and digestive capacity of S. aurata , but could modulate intestinal microbiota 65,92 …”