Selection of a L-Lysine-Overproducing Strain of the Red Seaweed Porphyra suborbiculata (Rhodophyta) through Mutation and Analog Enrichment

Abstract

Abstract An improved strain of the red seaweed Porphyra suborbiculata containing an increased amount of the essential amino acid l -lysine was obtained through mutation and analog enrichment. Mutagenesis using a 10% lethal dose of ultraviolet irradiation and an enrichment culture with the l -lysine analog aminoethyl- l -cysteine (AEC) was repeated to select the most productive strain us-ing monospores of P. suborbiculata . The concentrations of AEC required to produce 50 and 100% inhibition of survival were 60 and 115 mM in the parent strain, and 72 and 135 mM in the selected AEC-resistant strain, respectively. The AEC-resistant strain, L130, produced 1.74-fold more lysine compared to its parent strain. Thus, mutagenesis with analog enrichment shows promise for selecting seaweed strains that can overproduce this essential amino acid. Key words: Porphyra suborbiculata , Enrichment culture, Lysine, Mutation, Strain improvement Introduction The genus Porphyra (Bangiales, Rhodophyta) is one of the most important edible seaweeds cultivated commercially in Korea, Japan, and China. In 2009, the Korean aquaculture in-dustry produced 211,000 t (wet weight) from 57,000 ha (Korea Fisheries Association, 2010). This seaweed is highly prized for its flavor and as a health food rich in proteins, vitamins, and minerals.