title: Nitrate removal efficiency and bacterial community dynamics in denitrification processes using poly (L-lactic acid) as the solid substrate.
abstract: Laboratory-scale solid-phase denitrification (SPD) reactors for nitrate removal were constructed by acclimating activated sludge with poly (L-lactic acid) (PLLA) having weight-average molecular weights (M(w)) of 9,900, 12,000, and 45,100 g mol(-1). A good nitrate removal rate (3.5-5.3 mg NO(3)(-)-N g [dry wt](-1) h(-1)) was found in the reactor containing PLLA of 9,900 g mol(-1), whereas the other two reactors with the higher M(w) PLLA showed low nitrate removal efficiency. Microbial community dynamics in the low M(w) PLLA-acclimated reactor were studied by 16S rRNA gene-targeted PCR-denaturing gradient gel electrophoresis and quinone profiling. Nonmetric multidimensional scaling analyses of these data sets revealed a marked population shift during acclimation of the SPD reactor with low M(w) PLLA. The 16S rRNA gene clone library and culture-dependent analyses showed that bacteria belonging to the family Comamonadaceae predominated and played the primary role in denitrification in the PLLA-using reactor; however, none of the bacterial isolates from the reactor degraded PLLA. These results suggest that the nitrate removal property of the PLLA-using SPD reactor is attained through the bioavailability of hydrolysates released abiotically from the solid substrate.
authors.affiliation: Department of Environmental and Life Sciences, Toyohashi University of Technology, Aichi, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Takahashi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamada
authors.forename: Motohiro
authors.initials: M
authors.lastname: Tanno
authors.forename: Hideto
authors.initials: H
authors.lastname: Tsuji
authors.forename: Akira
authors.initials: A
authors.lastname: Hiraishi
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology; D058440:Denitrification; D019344:Lactic Acid / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009566:Nitrates / Q000378:metabolism*; D010802:Phylogeny; D011091:Polyesters; D011108:Polymers / Q000737:chemistry / Q000378:metabolism*; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*
chemical_list: D009566:Nitrates; D011091:Polyesters; D011108:Polymers; D012722:Sewage; D019344:Lactic Acid; C033616:poly(lactide)