Characterization of an Oleaginous Unicellular Green Microalga, Lobosphaera incisa (Reisigl, 1964) Strain K-1, Isolated From a Tidal Flat in the Yellow Sea, Republic of Korea.

Seungki Lee,Se Ra Lim,Ji Hyung Kim,Dae Gwin Jeong

doi:10.3389/fmicb.2018.02159

Abstract

Microalgae are considered as sustainable resources for biofuel production. However, recently the focus on microalgal research has shifted toward the investigation of high-value metabolites for potential pharmaceutical and nutritional applications. Herein, we report the identification of a novel oleaginous green microalga isolated from the Yellow Sea in Korea. We also describe the morphological, molecular, and biochemical characteristics of this microalga. On the basis of microscopic and genetic analyses, the isolate was classified as Lobosphaera incisa (the strain was designated as K-1), and molecular phylogeny revealed that the isolate distinctly differed from the other known L. incisa strains. The microalga could be cultivated in various commercial culture media under a relatively broad range of pH and temperature conditions. We also did a rough and detailed estimation of the different cellular components in the microalga. The composition of arachidonic acid (C20:4ω6) in the lipids of L. incisa strain K-1 was relatively high, similar to that in other strains, however, the K-1 strain had higher proportions of the ω3 series of fatty acids (FAs), including α-linolenic acid (C18:3ω3) and eicosapentaenoic acid (C20:5ω3), highlighting its uniqueness and strong potential for biotechnological application. To the best of our knowledge, this is the first report on the isolation of L. incisa from Korea as well as from a marine environment; this novel strain might be useful for the production of high-value ω3 and ω6 polyunsaturated fatty acids (PUFAs).

Highlights

Microalgae have been investigated as resources for alternative biofuel production
The parietal chloroplast found in the isolated microalga distinctively contained pyrenoids, traversed by many parallel thylakoid membranes; the presence of pyrenoids, which are considered to be the key feature in the taxonomical identification of L. incisa (Watanabe et al, 1996), suggested that the newly isolated microalga could be classified into the genus Lobosphaera
The focus of microalgal research has recently changed toward investigating the potential of microalgae to produce high-value metabolites other than biofuel

Summary

Introduction

Recently the research focus has changed toward using them as producers of high-value metabolites, such as antimicrobials, antioxidants, and polyunsaturated fatty acids (PUFAs), and nutritional supplements for humans and animals (Vanthoor-Koopmans et al, 2013). Among the high-value metabolites present in microalgae, PUFAs have recently been under increased focus owing to their potential therapeutic uses and nutritional applications (Pulz and Gross, 2004). Fish and shellfish are among the major food sources of ω3 and ω6 PUFAs, several studies have shown that microalgae have competitive advantages over fish oils as nutritional sources of these PUFAs for humans because of the lack of unpleasant odor and reduced risk of heavy metal contamination (Guil-Guerrero et al, 2000). Microalgal PUFAs have a very promising biotechnological potential both as food and feed, and several microalgal PUFA products are already commercially available (Pulz and Gross, 2004)

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