Discolored Red Seaweed Pyropia yezoensis with Low Commercial Value Is a Novel Resource for Production of Agar Polysaccharides

Abstract

The red seaweed Pyropia yezoensis has been demonstrated to be a novel resource for the production of high-quality agar. P. yezoensis is grown for the food industry in large-scale Japanese mariculture operations. However, discolored P. yezoensis is mostly discarded as an industrial waste, although it has some kind of utility values. Here, we evaluated the utility of discolored P. yezoensis as a resource for agar production. The quality of agar from the discolored seaweed was comparable to that from normal seaweed. In addition, as a distinguishing characteristic, agar yield was higher from discolored seaweeds than from normal types. Moreover, we successfully used agar from discolored P. yezoensis for bacterial plate media and DNA electrophoresis gels without agarose purification. Thus, our results demonstrate that discolored P. yezoensis is suitable for agar production and use in life science research. Diverting discolored P. yezoensis from disposal to agar production provides a solution to the current industrial waste problem in mariculture, as well as a secure source of agar for research purposes.

Successful Approaches for a Red Seaweed Biorefinery

“…Different strategies have been reported for the utilization of (i) the whole seaweed, either fresh or previously dried, (ii) food wastes and (iii) industrial wastes from the production of phycocolloids. Industrial food wastes, such as the discolored discarded seaweed can be a source for agar production, even with higher yields than from normal seaweeds [61]. A simple sequence could be defined for the energetic valorization of food wastes, such as those from Gracilaria lemaneiformis by microwave-assisted acid treatment to yield 16.3% levulinic acid and hydrochar with 45–55% yield and heating values of 19–25 MJ/kg [62].…”

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

“…For instance, from November 2016 to May 2017 in Hyogo Prefecture, Japan, it was reported that up to 16.7 tons (approximately 5,600,000 sheets) of discoloured laver sheet was deemed unfit for commercial use (Sasuga et al . 2018). However, since DLW has a low economic value, laver producers tend to either discard or not harvest DLW.…”

“…Agar is a widely used biomaterial for food production and biological research reagents for solid plate media and electrophoretic gels, and it is currently produced from red algae such as Gelidiales and Gracilariaceae (Sasuga et al . 2018). Although research on agar polysaccharide production from DLW is still rarely conducted, Sasuga et al .…”

“…Although research on agar polysaccharide production from DLW is still rarely conducted, Sasuga et al . (2018) recently proposed the use of discoloured P. yezoensis as a source for agar polysaccharide production. To obtain agar polysaccharide, discoloured laver materials were cut into small pieces and soaked in NaOH solution.…”

“…Agar polysaccharide extracted from discoloured laver is also suitable for bacterial plate media and DNA electrophoresis gels without purification (Sasuga et al . 2018). Zhang et al .…”