Comparative Transcriptome Profiling of Kappaphycus alvarezii (Rhodophyta, Solieriaceae) in Response to Light of Different Wavelengths and Carbon Dioxide Enrichment

A Proteomic Analysis for the Red Seaweed Asparagopsis taxiformis

The red seaweed Asparagopsis taxiformis is a promising ruminant feed additive with anti-methanogenic properties that could contribute to global climate change solutions. Genomics has provided a strong foundation for in-depth molecular investigations, including proteomics. Here, we investigated the proteome of A. taxiformis (Lineage 6) in both sporophyte and gametophyte stages, using soluble and insoluble extraction methods. We identified 741 unique non-redundant proteins using a genome-derived database and 2007 using a transcriptome-derived database, which included numerous proteins predicted to be of fungal origin. We further investigated the genome-derived proteins to focus on seaweed-specific proteins. Ontology analysis indicated a relatively large proportion of ion-binding proteins (i.e., iron, zinc, manganese, potassium and copper), which may play a role in seaweed heavy metal tolerance. In addition, we identified 58 stress-related proteins (e.g., heat shock and vanadium-dependent haloperoxidases) and 44 photosynthesis-related proteins (e.g., phycobilisomes, photosystem I, photosystem II and ATPase), which were in general more abundantly identified from female gametophytes. Forty proteins were predicted to be secreted, including ten rhodophyte collagen-alpha-like proteins (RCAPs), which displayed overall high gene expression levels. These findings provide a comprehensive overview of expressed proteins in A. taxiformis, highlighting the potential for targeted protein extraction and functional characterisation for future biodiscovery.

Improvement of Biomass and Phycoerythrin Production by a Strain of Rhodomonas sp. Isolated from the Tunisian Coast of Sidi Mansour

Microalgae are photoautotrophic microorganisms known as producers of a large variety of metabolites. The taxonomic diversity of these microorganisms has been poorly explored. In this study, a newly isolated strain was identified based on the 18S rRNA encoding gene. The phylogenetic analysis showed that the isolated strain was affiliated with the Rhodomonas genus. This genus has greatly attracted scientific attention according to its capacity to produce a large variety of metabolites, including phycoerythrin. Growth and phycoerythrin production conditions were optimized using a Plackett–Burman design and response surface methodology. An expression profile analysis of the cpeB gene, encoding the beta subunit of phycoerythrin, was performed by qRT-PCR under standard and optimized culture conditions. The optimization process showed that maximum cell abundance was achieved under the following conditions: CaCl2 = 2.1328 g/L, metal solution = 1 mL/L, pH = 7 and light intensity = 145 μmol photons/m2/s, whereas maximum phycoerythrin production level occurred when CaCl2 = 1.8467 g/L, metal solution = 1 mL/L, pH = 7 and light intensity = 157 μmol/m2/s. In agreement, positive transcriptional regulation of the cpeB gene was demonstrated using qRT-PCR. This study showed the successful optimization of abiotic conditions for highest growth and phycoerythrin production, making Rhodomonas sp. suitable for several biotechnological applications.

Carrageenan From Kappaphycus alvarezii (Rhodophyta, Solieriaceae): Metabolism, Structure, Production, and Application

Carrageenan is a polysaccharide derived from red algae (seaweed) with enormous economic potential in a wide range of industries, including pharmaceuticals, food, cosmetics, printing, and textiles. Carrageenan is primarily produced through aquaculture-based seaweed farming, with Eucheuma and Kappaphycus species accounting for more than 90% of global output. There are three major types of carrageenan found in red algae: kappa (κ)-, iota (ι)-, and lambda (λ)-carrageenan. Kappaphycus alvarezii is the most common kappa-carrageenan source, and it is primarily farmed in Asian countries such as Indonesia, the Philippines, Vietnam, and Malaysia. Carrageenan extracted from K. alvarezii has recently received a lot of attention due to its economic potential in a wide range of applications. This review will discuss K. alvarezii carrageenan in terms of metabolic and physicochemical structure, extraction methods and factors affecting production yield, as well as current and future applications.