Nutritional Composition of the Atlantic Seaweeds Ulva rigida, Codium tomentosum, Palmaria palmata and Porphyra purpurea

Macroalgae are regarded as a healthy food due to their composition and nutritional properties. In this work, nutritional composition of two green (Ulva rigida, Codium tomentosum) and two red (Palmaria palmata, Porphyra purpurea) edible seaweed was studied. Total lipids were measured gravimetrically as evaporated mass after petroleum-ether Soxhlet extraction of samples. In addition, fatty acid profile was determined by gas chromatography coupled to a flame ionization detector (GC-FID). Results showed that all studied species were accounted for very low levels of lipids (<1% dw), but levels of unsaturated fatty acids oleic, linoleic, and linolenic acids were present at high concentrations, with P. palmata displaying the highest quantities (>200 mg C18:1/g extract). In parallel, proteins were quantified following the macro-Kjeldahl method. In this analysis, red algae, especially P. purpurea, showed significant protein content up to 30% DW. Total organic acids were found by ultra-filtration liquid-chromatography coupled to an amperometry detector (UFLC-PAD) after an acid extraction, P. purpurea being the algae with the higher organic acid content (10.61% dw). Minerals were identified and quantified by inductively coupled plasma atomic emission spectroscopy (ICP-OES), suggesting that both algae groups are rich in K and Mg (>15 g/kg), but U. rigida also displayed a remarkable iron content (>1 g Fe/kg). Other detected minerals in minor concentrations were Ca, P or F. Altogether, results corroborate that these edible algae are a good source of nutrients in accordance with literature.

Metagenomic profiling of host-associated bacteria from 8 datasets of the red alga Porphyra purpurea, with MetaPhlAn 3.0

Microbial communities play a fundamental role in the association with marine algae, in fact they are recognized to be actively involved in growth and morphogenesis.Porphyra purpurea is a red algae commonly found in the intertidal zone with an high economical value, indeed several species belonging to the genus Porphyra are intensely cultivated in the Eastern Asian countries. Moreover, P. purpurea is widely used as model species in different fields, mainly due to its peculiar life cycle. Despite of that, little is known about the microbial community associated to this species. Here we report the microbial-associated diversity of P. purpurea in four different localities (Ireland, Italy United Kingdom and USA) through the analysis of eight metagenomic datasets obtained from the publicly available metagenomic nucleotide database (https://www.ebi.ac.uk/ena/). The metagenomic datasets were quality controlled with FastQC version 0.11.8, pre-processed with Trimmomatic version 0.39 and analysed with Methaplan 3.0, with a reference database containing clade specific marker genes from ~ 99.500 bacterial genomes, following the pan-genome approach, in order to identify the putative bacterial taxonomies and their relative abundances. Furthermore, we compared the results to the 16S rRNA metagenomic analysis pipeline of MGnify database to evaluate the effectiveness of the two methods. Out of the 43 bacterial species identified with MetaPhlAn 3.0 only 5 were common with the MGnify results and from the 21 genera, only 9 were common. This approach highlighted the different taxonomical resolution of a 16S rRNA OTU-based method in contrast to the pan-genome approach deployed by MetaPhlAn 3.0.