title: Medium chain length polyhydroxyalkanoate (mcl-PHA) production from volatile fatty acids derived from the anaerobic digestion of grass.
abstract: A two step biological process for the conversion of grass biomass to the biodegradable polymer medium chain length polyhydroxyalkanoate (mcl-PHA) was achieved through the use of anaerobic and aerobic microbial processes. Anaerobic digestion (mixed culture) of ensiled grass was achieved with a recirculated leach bed bioreactor resulting in the production of a leachate, containing 15.3 g/l of volatile fatty acids (VFAs) ranging from acetic to valeric acid with butyric acid predominating (12.8 g/l). The VFA mixture was concentrated to 732.5 g/l with a 93.3 % yield of butyric acid (643.9 g/l). Three individual Pseudomonas putida strains, KT2440, CA-3 and GO16 (single pure cultures), differed in their ability to grow and accumulate PHA from VFAs. P. putida CA-3 achieved the highest biomass and PHA on average with individual fatty acids, exhibited the greatest tolerance to higher concentrations of butyric acid (up to 40 mM) compared to the other strains and exhibited a maximum growth rate (μMAX = 0.45 h⁻¹). Based on these observations P. putida CA-3 was chosen as the test strain with the concentrated VFA mixture derived from the AD leachate. P. putida CA-3 achieved 1.56 g of biomass/l and accumulated 39 % of the cell dry weight as PHA (nitrogen limitation) in shake flasks. The PHA was composed predominantly of 3-hydroxydecanoic acid (>65 mol%).
authors.affiliation: Technology Centre for Biorefining and Bioenergy, Orbsen Building, National University of Ireland, Galway, Ireland.
authors.forename: Federico
authors.initials: F
authors.lastname: Cerrone
authors.forename: Santosh K
authors.initials: SK
authors.lastname: Choudhari
authors.forename: Reeta
authors.initials: R
authors.lastname: Davis
authors.forename: Denise
authors.initials: D
authors.lastname: Cysneiros
authors.forename: Vincent
authors.initials: V
authors.lastname: O'Flaherty
authors.forename: Gearoid
authors.initials: G
authors.lastname: Duane
authors.forename: Eoin
authors.initials: E
authors.lastname: Casey
authors.forename: Maciej W
authors.initials: MW
authors.lastname: Guzik
authors.forename: Shane T
authors.initials: ST
authors.lastname: Kenny
authors.forename: Ramesh P
authors.initials: RP
authors.lastname: Babu
authors.forename: Kevin
authors.initials: K
authors.lastname: O'Connor
mesh_terms: D019149:Bioreactors; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D006109:Poaceae / Q000378:metabolism*; D054813:Polyhydroxyalkanoates / Q000378:metabolism*; D016958:Pseudomonas putida / Q000378:metabolism*
chemical_list: D005232:Fatty Acids, Volatile; D054813:Polyhydroxyalkanoates