title: Shifting the balance of fermentation products between hydrogen and volatile fatty acids: microbial community structure and function.
abstract: Fermentation is a key process in many anaerobic environments. Varying the concentration of electron donor fed to a fermenting community is known to shift the distribution of products between hydrogen, fatty acids and alcohols. Work to date has focused mainly on the fermentation of glucose, and how the microbial community structure is affected has not been explored. We fed ethanol, lactate, glucose, sucrose or molasses at 100 me- eq. L-1, 200 me- eq. L-1or 400 me- eq. L-1to batch-fed cultures with fermenting, methanogenic communities. In communities fed high concentrations of electron donor, the fraction of electrons channeled to methane decreased, from 34% to 6%, while the fraction of electrons channeled to short chain fatty acids increased, from 52% to 82%, averaged across all electron donors. Ethanol-fed cultures did not produce propionate, but did show an increase in electrons directed to acetate as initial ethanol concentration increased. In glucose, sucrose, molasses and lactate-fed cultures, propionate accumulation co-occurred with known propionate producing organisms. Overall, microbial communities were determined by the substrate provided, rather than its initial concentration, indicating that a change in community function, rather than community structure, is responsible for shifts in the fermentation products produced.
authors.affiliation: Swette Center for Environmental Biotechnology, Arizona State University, 1001 S. McAllister Ave, Tempe 85287, Arizona, USA.
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Miceli
authors.affiliation: Environmental Biotechnology, Arizona State University, 1001 S. McAllister Ave, Tempe 85287, Arizona, USA.
authors.forename: César I
authors.initials: CI
authors.lastname: Torres
authors.affiliation: Environmental Biotechnology, Arizona State University, 1001 S. McAllister Ave, Tempe 85287, Arizona, USA dr.rosy@asu.edu.
authors.forename: Rosa
authors.initials: R
authors.lastname: Krajmalnik-Brown
mesh_terms: D000085:Acetates / Q000378:metabolism; D000693:Anaerobiosis / Q000502:physiology; D001438:Bacteroidaceae / Q000378:metabolism*; D019149:Bioreactors; D000068016:Eubacteriales / Q000378:metabolism*; D000431:Ethanol / Q000737:chemistry; D005232:Fatty Acids, Volatile / Q000096:biosynthesis*; D005285:Fermentation / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D006859:Hydrogen / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008697:Methane / Q000096:biosynthesis*; D008965:Molasses; D010100:Oxygen / Q000378:metabolism*; D011422:Propionates / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism
chemical_list: D000085:Acetates; D005232:Fatty Acids, Volatile; D011422:Propionates; D000431:Ethanol; D013395:Sucrose; D006859:Hydrogen; D005947:Glucose; D008697:Methane; D010100:Oxygen
keywords: concentration; fermentation; methanogenesis; microbial community; propionate production; sugars