Discoloration in the marine red algae Pyropia: causative factors and exploiting the biotechnological potential of a waste resource

Abstract

Pyropia (Porphyra, referred to as ‘Gim’ in Korea or ‘Nori’ in Japan), an economically valuable alga, has long been consumed as seafood, especially in north‐east Asian countries. Its well‐established conventional mass cultivation and harvesting methods in coastal areas widen the industrial availability of edible Pyropia sp. However, the unexpected discoloration derived from causative factors during the cultivation process gives rise to serious economic losses in the aquaculture industry. For the industrial use of discoloured laver waste (DLW), recent articles have suggested that DLW biomass could be used as a source of agar polysaccharide, porphyran, γ‐aminobutyric acid and other value‐added bioactive compound productions. Although DLW biomass has economic potential, the lack of integrated information and relevant studies still limits its industrial availability. Therefore, we discussed recent research concerning the functional ingredients, causative factors and potential availability of DLW to provide integrated information. Furthermore, this review suggested the potential industrial application of DLW as a source for other value‐added material production.

Valorization of waste materials from seaweed industry: An industry survey based biorefinery approach

“…A recent FAO report indicates that the global seaweed production in 2019 was about 35 million tonnes in terms of fresh weight (more than 96% of the total production from aquaculture), and this production estimate accounts for nearly a quarter of the world aquaculture production 16,17 . Whether seaweeds are sourced from cultivation (i.e., onshore and offshore farms) or wild collection, it should be emphasized that a significant amount of waste materials are likely generated during harvesting or post‐harvest processing steps 10,15 . Importantly, different waste materials may contain a number of valuable compounds that could be further processed, concentrated or refined to produce biofuels and bioproducts 3,18 .…”

“…In addition to the processing steps of harvested seaweeds, a significant economic loss due to biofouling or discoloration of seaweeds has been reported annually in seaweed farms globally, and the amount of low‐quality biomass that does not meet commercial quality standards could be substantial. According to Sasuga et al, up to 16.7 tons of discoloured laver was deemed unfit for commercial use from November 2016 to May 2017 in Hyogo Prefecture, Japan, and seaweed producers did not harvest these low‐quality seaweeds, which in turn caused environmental pollution in the area 10,23 . Likewise, in Seocheon‐gun, South Korea, almost $20 million of economic loss was reported in 2011 due to the degradation of seaweed quality caused by nutrient depletion and pathogenic infection 10 .…”

“…According to Sasuga et al, up to 16.7 tons of discoloured laver was deemed unfit for commercial use from November 2016 to May 2017 in Hyogo Prefecture, Japan, and seaweed producers did not harvest these low‐quality seaweeds, which in turn caused environmental pollution in the area 10,23 . Likewise, in Seocheon‐gun, South Korea, almost $20 million of economic loss was reported in 2011 due to the degradation of seaweed quality caused by nutrient depletion and pathogenic infection 10 . However, even though these low‐quality seaweeds are not suitable for human consumption, nutritional constituents available in the biomass may present opportunities for their utilization in different industrial sectors 24 …”

“…While the market share of direct consumption of whole seaweed biomass continues to grow in the global market, 2,10 current extraction processes of chemicals from seaweeds are focused on a single target product, such as hydrocolloids, colourants and phenolic compounds 2 . For instance, the seaweed hydrocolloid industry primarily produces different grades of agar, alginate and carrageenan by processing over a million wet tonnes of seaweeds annually (mostly red and brown seaweeds, including Eucheuma , Gracilaria and Gelidium ) 11 ; and these seaweed polysaccharides generate over US $1 billion sales 12 .…”

“…Similarly, Polikovsky et al demonstrated that hydrochar production can be combined with the co‐production of ethanol, proteins and additional hydrolyzed monomers from ‘waste’ seaweed biomass 14 . In addition, Cho et al reported a substantial loss of edible seaweed Pyropia due to the discoloration caused by nutrient depletion or pathogens, and proposed the utilization of low‐quality discoloured laver in the production of value‐added compound 10 . Therefore, a substantial amount of waste materials available in both seaweed harvesting and processing sectors could serve as an untapped resource with new market opportunities.…”