Community structure evolution and enrichment of glycogen-accumulating organisms producing polyhydroxyalkanoates from fermented molasses.
An open mixed culture was enriched with glycogen-accumulating organisms (GAOs) by using a sequencing batch reactor and treating an agroindustrial waste (sugar cane molasses) under cyclic anaerobic-aerobic conditions. Over a 1-year operating period, the culture exhibited a very stable GAO phenotype with an average polyhydroxyalkanoate (PHA) content of 17% total suspended solids. However, the GAO microbial community evolved over the course of operation to a culture exhibiting unusual characteristics in producing PHAs comprised of short-chain-length monomers, namely, 3-hydroxybutyrate, 3-hydroxy-2-methylbutyrate, 3-hydroxyvalerate, and 3-hydroxy-2-methylvalerate, and also, up to 31 mol% of the medium-chain-length (MCL) monomer 3-hydroxyhexanoate (3HHx). Microbial community analysis by fluorescence in situ hybridization revealed a concurrent long-term drift in the GAO community balance, from mainly "Candidatus Competibacter phosphatis" to mainly Defluviicoccus vanus-related organisms. The production of 3HHx was confirmed by (13)C nuclear magnetic resonance (NMR) and appeared to be related to the increased presence of D. vanus-related GAOs. These results suggest a broadened spectrum of material, chemical, and mechanical properties that can be achieved for biopolymers produced by open mixed cultures from fermented waste. The increased spectrum of polymer properties brings a wider scope of potential applications.
Pisco
Ana R
AR
REQUIMTE/CQFB, Chemistry Department, FCT/Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
Bengtsson
Simon
S
Werker
Alan
A
Reis
Maria A M
MA
Lemos
Paulo C
PC
D001419:Bacteria / Q000145:classification* / Q000302:isolation & purification / Q000378:metabolism*; D044822:Biodiversity; D004269:DNA, Bacterial / Q000235:genetics; D006003:Glycogen / Q000378:metabolism*; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D009682:Magnetic Resonance Spectroscopy; D008965:Molasses / Q000382:microbiology*; D054813:Polyhydroxyalkanoates / Q000378:metabolism*
D004269:DNA, Bacterial; D054813:Polyhydroxyalkanoates; D006003:Glycogen