title: Acidophilic green alga Pseudochlorella sp. YKT1 accumulates high amount of lipid droplets under a nitrogen-depleted condition at a low-pH.
abstract: Microalgal storage lipids are considered to be a promising source for next-generation biofuel feedstock. However, microalgal biodiesel is not yet economically feasible due to the high cost of production. One of the reasons for this is that the use of a low-cost open pond system is currently limited because of the unavoidable contamination with undesirable organisms. Extremophiles have an advantage in culturing in an open pond system because they grow in extreme environments toxic to other organisms. In this study, we isolated the acidophilic green alga Pseudochlorella sp. YKT1 from sulfuric acid mine drainage in Nagano Prefecture, Japan. The vegetative cells of YKT1 display the morphological characteristics of Trebouxiophyceae and molecular phylogenetic analyses indicated it to be most closely related to Pseudochlorella pringsheimii. The optimal pH and temperature for the growth of YKT1 are pH 3.0-5.0 and a temperature 20-25°C, respectively. Further, YKT1 is able to grow at pH 2.0 and at 32°C, which corresponds to the usual water temperature in the outdoors in summer in many countries. YKT1 accumulates a large amount of storage lipids (∼30% of dry weigh) under a nitrogen-depleted condition at low-pH (pH 3.0). These results show that acidophilic green algae will be useful for industrial applications by acidic open culture systems.
authors.affiliation: Center for Frontier Research, National Institute of Genetics, Mishima, Shizuoka, Japan; Japan Science and Technology Agency, CREST, Kawaguchi, Saitama, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Hirooka
authors.affiliation: Suzaka, Nagano, Japan.
authors.forename: Sumio
authors.initials: S
authors.lastname: Higuchi
authors.affiliation: Center for Frontier Research, National Institute of Genetics, Mishima, Shizuoka, Japan; Department of Genetics, Graduate University for Advanced Studies (SOKENDAI), Mishima, Shizuoka, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Uzuka
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Nozaki
authors.affiliation: Center for Frontier Research, National Institute of Genetics, Mishima, Shizuoka, Japan; Japan Science and Technology Agency, CREST, Kawaguchi, Saitama, Japan; Department of Genetics, Graduate University for Advanced Studies (SOKENDAI), Mishima, Shizuoka, Japan.
authors.forename: Shin-ya
authors.initials: SY
authors.lastname: Miyagishima
mesh_terms: D056804:Biofuels; D000460:Chlorophyta / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007564:Japan; D066292:Lipid Droplets / Q000378:metabolism*; D050356:Lipid Metabolism; D009584:Nitrogen / Q000378:metabolism; D010802:Phylogeny
chemical_list: D056804:Biofuels; D009584:Nitrogen