Mimicking Lichens: Incorporation of Yeast Strains Together with Sucrose-Secreting Cyanobacteria Improves Survival, Growth, ROS Removal, and Lipid Production in a Stable Mutualistic Co-Culture Production Platform

Michael Guarnieri, Tingting Li, Chien-Ting Li, Kirk Butler, Stephanie Hays, George Oyler, Michael Betenbaugh

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67 Scopus Citations

Abstract

Background: The feasibility of heterotrophic-phototrophic symbioses was tested via pairing of yeast strains Cryptococcus curvatus, Rhodotorula glutinis, or Saccharomyces cerevisiae with a sucrose-secreting cyanobacterium Synechococcus elongatus. Results: The phototroph S. elongatus showed no growth in standard BG-11 medium with yeast extract, but grew well in BG-11 medium alone or supplemented with yeast nitrogen base without amino acids (YNB w/o aa). Among three yeast species, C. curvatus and R. glutinis adapted well to the BG-11 medium supplemented with YNB w/o aa, sucrose, and various concentrations of NaCl needed to maintain sucrose secretion from S. elongatus, while growth of S. cerevisiae was highly dependent on sucrose levels. R. glutinis and C. curvatus grew efficiently and utilized sucrose produced by the partner in co-culture. Co-cultures of S. elongatus and R. glutinis were sustained over 1 month in both batch and in semi-continuous culture, with the final biomass and overall lipid yields in the batch co-culture 40 to 60% higher compared to batch mono-cultures of S. elongatus. The co-cultures showed enhanced levels of palmitoleic and linoleic acids. Furthermore, cyanobacterial growth in co-culture with R. glutinis was significantly superior to axenic growth, as S. elongatus was unable to grow in the absence of the yeast partner when cultivated at lower densities in liquid medium. Accumulated reactive oxygen species was observed to severely inhibit axenic growth of cyanobacteria, which was efficiently alleviated through catalase supply and even more effectively with co-cultures of R. glutinis. Conclusions: The pairing of a cyanobacterium and eukaryotic heterotroph in the artificial lichen of this study demonstrates the importance of mutual interactions between phototrophs and heterotrophs, e.g., phototrophs provide a carbon source to heterotrophs, and heterotrophs assist phototrophic growth and survival by removing/eliminating oxidative stress. Our results establish a potential stable production platform that combines the metabolic capability of photoautotrophs to capture inorganic carbon with the channeling of the resulting organic carbon directly to a robust heterotroph partner for producing biofuel and other chemical precursors.

Original languageAmerican English
Article number55
Number of pages11
JournalBiotechnology for Biofuels
Volume10
Issue number1
DOIs
StatePublished - 2017

Bibliographical note

Publisher Copyright:
© 2017 The Author(s).

NREL Publication Number

  • NREL/JA-5100-68306

Keywords

  • Artificial lichen
  • Co-culture
  • Cyanobacteria
  • Hydrogen peroxide
  • Lipid production
  • ROS
  • Sucrose
  • Yeasts

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