Valorization of the Red Algae Gelidium sesquipedale by Extracting a Broad Spectrum of Minor Compounds Using Green Approaches

Until now, the red algae Gelidium sesquipedale has been primarily exploited for agar production, leaving an undervalued biomass. In this work, the use of eco-friendly approaches employing ultrasound-assisted extraction (UAE) and green solvents was investigated to valorize the algal minor compounds. The green methods used herein showed an attractive alternative to efficiently extract a broad spectrum of bioactive compounds in short extraction times (15 to 30 min vs. 8 h of the conventional method). Using the best UAE conditions, red seaweed extracts were characterized in terms of total phenolics (189.3 ± 11.7 mg GAE/100 g dw), flavonoids (310.7 ± 9.7 mg QE/100 g dw), mycosporine-like amino acids (MAAs) (Σ MAAs = 1271 mg/100 g dw), and phycobiliproteins (72.4 ± 0.5 mg/100 g dw). Additionally, produced algal extracts exhibited interesting antioxidant and anti-enzymatic activities for potential applications in medical and/or cosmetic products. Thus, this study provides the basis to reach a superior valorization of algal biomass by using alternative methods to extract biologically active compounds following eco-friendly approaches. Moreover, the strategies developed not only open new possibilities for the commercial use of Gelidium sesquipedale, but also for the valorization of different algae species since the techniques established can be easily adapted.

IMPROVING THE DURABILITY OF CULTIVATOR BLADES USING ONE-SIDED GAS-FLAME SURFACING

In agar production one of the most common technological operations is cutting of soil or plants. It makes up at least 70% of the total volume of mechanized works. The purpose of this study is to help maintain the agrotechnological parameters of the cultivator's blade by coating the blade with powder wear-resistant coatings using the one-sided gas-flame surfacing technology. The technology of strengthening the cultivator blade using one-sided gas-flame surfacing is applied. As a result, were defined: powder granulation on the thickness of the applied layer; modes and parameters of the one-sided gas-flame surfacing during the formation of composite material coating. Foreign experience of the last decades shows that with the development of gasometric spraying methods it is possible to atomize various materials such as polymers, carbides, metals. These coatings withstand the impact of high thermal loads, shock-abrasive and chemically active environments. Comparison of application methods mentioned above shows that the quality of coatings expressed in the parameters: adhesions, porosity, oxidation levels remain at approximately the same level. However, a comparative analysis of foreign practice has shown that the method of gas-flame surfacing is more technological, more productivity, and the specific costs of the coating are reduced.

Comprehensive analysis and identification of heat-responsive genes in Agarophyton vermiculophyllum by RNA-sequencing

Agarophyton vermiculophyllum is a commercially important red alga for agar production in the Northwest Pacific Ocean and is an invasive seaweed in Europe. High temperature is an important environmental stressor that influences its growth, metabolism, and migration. Nevertheless, little is known about the molecular mechanisms underpinning the response of A. vermiculophyllum to heat stress. Using RNA-sequencing, we performed the first comprehensive transcriptome analysis of A. vermiculophyllum under heat stress to explore and identify potentially important heat stress-responsive genes. After de novo assembly of the transcriptome, 55,486 unigenes were found, of which 39,687 unigenes (71.52%) were functionally annotated. In total, 2,923 differentially expressed genes (DEGs) were detected between heat-stressed and control samples. Heat shock proteins represented the most abundant DEGs. Transcript factors were also significantly differently expressed under heat stress. Meanwhile, the photoprotective mechanism based on PsbS (Photosystem II subunit S) related nonphotochemical quenching and PGR5 (proton gradient regulation 5) dependent cyclic electron flow around photosystem I was found to be promoted under heat stress, which may help A. vermiculophyllum to cope with the high temperature. This study lays an important foundation for further elucidation of the molecular mechanism underlying heat tolerance in A. vermiculophyllum.

Trends in seaweed resource use and aquaculture in South Africa and Namibia over the last 30 years

The seaweed industry of temperate Southern Africa was last reviewed in 2003. Since then there have been considerable changes. There are three main uses of kelp (mostly Ecklonia maxima, with some Laminaria pallida) in South Africa. The collection of wash-up for drying and exporting for alginate extraction has drastically reduced to very small amounts in recent years. The boat harvest of fresh kelp for abalone feed in land-based farms has reached a plateau of between 4000 and 5000 t fresh per annum. The diver harvest of E. maxima for agricultural liquid plant growth enhancer shows a constant increase over several years, is still growing, and is currently over 3000 t fresh per annum. The small intertidal collection of Gelidium pristoides as export for agar production has maintained a small, sustainable production of around 100 t dry for many years. Former Gracilaria industries in sheltered bays in both South Africa and Namibia have collapsed, and there is currently no commercial collection. There was commercial raft aquaculture production of Gracilaria in Lüderitz Bay, Namibia for a number of years, but this is no longer practised. Currently, the only commercial seaweed use in Namibia is of L. pallida. Annually, ca. 150 t of fresh wash-up is collected, in Lüderitz, to be used as feed in land-based abalone aquaculture. There are a number of small start-up companies experimenting with seaweed products for cosmetics and nutritional products in both countries, some involving species of Ulva and Porphyra. The former species is a major aquaculture product, with around 2000 t fresh yr–1 being produced in integrated land-based systems with abalone.

Seaweed utilisation in New Zealand

The commercial landscape of seaweed use in New Zealand (NZ) has shifted and evolved since it was last reviewed in 2006. One of the largest changes saw the introduction of Macrocystis pyrifera and green-lipped mussel spat (which is landed attached to beach-cast seaweed) into the Quota Management System—the primary tool for commercial fisheries management in NZ. There have also been policy changes around commercial harvesting and farming of Undaria pinnatifida, an introduced brown alga native to Asia. Traditionally, commercial algal utilization has been limited to agar production and beach-cast collection for aquaculture feeds, though demand for seaweed products has increased with a growing Asian population in NZ. The NZ seaweed industry is at an early developmental stage, but it has the potential to offer high quality seaweed stock and value-added products to the world market. The exploration of seaweed farming, the growing demand for seaweed fertilizers and the development of high-value bioactive products such as fucoidan has attracted interest from marine farmers and entrepreneurs. The key to success for the NZ seaweed industry rests in developing high-value products for an export market, from integrated farming, harvesting and processing that can deliver the most value, consume the least energy and generate minimal waste.