Title: 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

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 fnal 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 signifcantly superior to axenic growth, as S. elongatus was unable to grow in the absence of the yeastmore » 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 artifcial 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.« less

Authors:

Li, Tingting; Li, Chien-Ting; Butler, Kirk; Hays, Stephanie G.; Guarnieri, Michael T.; Oyler, George A.; Betenbaugh, Michael J.

Publication Date:

Tue Mar 21 00:00:00 EDT 2017

Research Org.:

National Renewable Energy Laboratory (NREL), Golden, CO (United States); Johns Hopkins Univ., Baltimore, MD (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE)

OSTI Identifier:

1618671

Alternate Identifier(s):

OSTI ID: 1351861; OSTI ID: 1485587

Report Number(s):

NREL/JA-5100-68306
Journal ID: ISSN 1754-6834; 55; PII: 736

Grant/Contract Number:  

DE‐SC0012658; SC0012658; AC36-08GO28308

Resource Type:

Published Article

Journal Name:

Biotechnology for Biofuels

Additional Journal Information:

Journal Name: Biotechnology for Biofuels Journal Volume: 10 Journal Issue: 1; Journal ID: ISSN 1754-6834

Publisher:

Springer Science + Business Media

Country of Publication:

Netherlands

Language:

English

Subject:

09 BIOMASS FUELS; 59 BASIC BIOLOGICAL SCIENCES; cyanobacteria; yeasts; co-culture; sucrose; ROS; artificial lichen; hydrogen peroxide; lipid production; Co‑culture; Artifcial lichen