title: Succinate and Lactate Production fromEuglena gracilisduring Dark, Anaerobic Conditions.
abstract: Euglena gracilisis a eukaryotic, unicellular phytoflagellate that has been widely studied in basic science and applied science. Under dark, anaerobic conditions, the cells ofE. gracilisproduce a wax ester that can be converted into biofuel. Here, we demonstrate that under dark, anaerobic conditions,E. gracilisexcretes organic acids, such as succinate and lactate, which are bulk chemicals used in the production of bioplastics. The levels of succinate were altered by changes in the medium and temperature during dark, anaerobic incubation. Succinate production was enhanced when cells were incubated in CM medium in the presence of NaHCO3. Excretion of lactate was minimal in the absence of external carbon sources, but lactate was produced in the presence of glucose during dark, anaerobic incubation.E. gracilispredominantly produced L-lactate; however, the percentage of D-lactate increased to 28.4% in CM medium at 30°C. Finally, we used a commercial strain ofE. gracilisfor succinate production and found that nitrogen-starved cells, incubated under dark, anaerobic conditions, produced 869.6 mg/L succinate over a 3-day incubation period, which was 70-fold higher than the amount produced by nitrogen-replete cells. This is the first study to demonstrate organic acid excretion byE. graciliscells and to reveal novel aspects of primary carbon metabolism in this organism.
authors.affiliation: School of Agriculture, Meiji University Kawasaki, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tomita
authors.affiliation: School of Agriculture, Meiji University Kawasaki, Japan.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Yoshioka
authors.affiliation: School of Agriculture, Meiji University Kawasaki, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Iijima
authors.affiliation: euglena Co., Ltd Tokyo, Japan.
authors.forename: Ayaka
authors.initials: A
authors.lastname: Nakashima
authors.affiliation: euglena Co., Ltd Tokyo, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Iwata
authors.affiliation: euglena Co., Ltd Tokyo, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Graduate School of Science, Technology and Innovation, Kobe University Kobe, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Hasunuma
authors.affiliation: Graduate School of Science, Technology and Innovation, Kobe University Kobe, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
authors.affiliation: RIKEN Center for Sustainable Resource Science Yokohama, Japan.
authors.forename: Masami Yokota
authors.initials: MY
authors.lastname: Hirai
authors.affiliation: School of Agriculture, Meiji UniversityKawasaki, Japan; RIKEN Center for Sustainable Resource ScienceYokohama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Osanai
keywords: Euglena; biorefinery; lactate; microalgae; succinate