Effects of Escherichia coli on mixotrophic growth of Chlorella minutissima and production of biofuel precursors

• Published in: PloS one Vol. 9; no. 5; p. e96807
• Main Authors: Higgins, Brendan T, VanderGheynst, Jean S
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 07.05.2014; Public Library of Science (PLoS)
• Subjects: Acetic acid; Agricultural engineering; Algae; Analysis; Bacteria; Biofouling; Biofuels; Biofuels - microbiology; Biology and Life Sciences; Biomass; Biomass energy; Bioreactors; Carbon; Carbon - metabolism; Chlorella; Chlorella - genetics; Chlorella - growth & development; Chlorella - metabolism; Chlorella minutissima; Chlorella pyrenoidosa; Chlorella sorokiniana; Chlorella vulgaris; Coculture Techniques; Contamination; Culture Media; E coli; Engineering and Technology; Escherichia coli; Escherichia coli - genetics; Escherichia coli - growth & development; Escherichia coli - metabolism; Fatty acids; Food contamination & poisoning; Fuels; Glucose; Glucose - biosynthesis; Glycerol; Humans; Lipids; Microbiology; Nitrogen; Nutrients; Precursors; Reactors; Researchers; Starch; Starch - biosynthesis; Studies; Substrates; Water treatment; California
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0096807

Chlorella minutissima was co-cultured with Escherichia coli in airlift reactors under mixotrophic conditions (glucose, glycerol, and acetate substrates) to determine possible effects of bacterial contamination on algal biofuel production. It was hypothesized that E. coli would compete with C. minutissima for nutrients, displacing algal biomass. However, C. minutissima grew more rapidly and to higher densities in the presence of E. coli, suggesting a symbiotic relationship between the organisms. At an initial 1% substrate concentration, the co-culture produced 200-587% more algal biomass than the axenic C. minutissima cultures. Co-cultures grown on 1% substrate consumed 23-737% more of the available carbon substrate than the sum of substrate consumed by E. coli and C. minutissima alone. At 1% substrate, total lipid and starch productivity were elevated in co-cultures compared to axenic cultures indicating that bacterial contamination was not detrimental to the production of biofuel precursors in this specific case. Bio-fouling of the reactors observed in co-cultures and acid formation in all mixotrophic cultures, however, could present challenges for scale-up.