Nitrate Removal Efficiency and Bacterial Community Dynamics in Denitrification Processes Using Poly (<sc>L</sc>-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 (Mw) of 9,900, 12,000, and 45,100 g mol −1 . A good nitrate removal rate (3.5-5.3 mg NO3 − -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 Mw PLLA showed low nitrate removal efficiency. Microbial community dynamics in the low Mw 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 Mw 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.

N₂O Emission from Degraded Soybean Nodules Depends on Denitrification by <i>Bradyrhizobium japonicum</i> and Other Microbes in the Rhizosphere

“…Prokaryotic denitrification, fungal denitrification, ammonium oxidation, and nitrate ammonification have been nominated as soil microbial sources of N 2 O (1, 14, 26, 38, 49, 50, 57). Community analysis specific to degrading nodules that emit N 2 O found many microorganisms that potentially produce N 2 O (20), including denitrifying bacteria such as Acidovorax (19) and Enterobacter (2); Bradyrhizobium (25), Salmonella (48), Xanthomonas (52), and Pseudomonas (36), which have functional genes and/or activities for denitrification; and Fusarium , a denitrifying fungus (45).…”

Ecological Perspectives on Microbes Involved in N-Cycling

“…The N cycle has also been the focus of debate in nitrogen-rich ecosystems, such as fertilized agricultural fields or eutrophic rivers and coasts that are affected by anthropogenic N input (48, 53, 85, 90, 101, 110, 114, 115, 134, 135). Wastewater treatment systems are also examples of artificial ecosystems in which N removal is frequently studied (29, 78, 116, 121). Studies on the pathways and rates of input, output, and internal cycle of N and its interactions with other elements can provide insights into the fundamental issues related to ecosystem ecology.…”

Nitrate removal performance of Diaphorobacter nitroreducens using biodegradable plastics as the source of reducing power

“…The resultant supernatant samples were filtered through membrane filters (pore size, 0.2 µm) and directly subjected to analysis or stored at -20°C until use. The concentrations of nitrate and nitrite were analyzed by ion chromatography as described previously [14].…”

“…External solid substrates widely used for the SPD process are biodegradable polyesers applied as biodegradable plastics, such as poly(3-hydroxybutyrate) (PHB) [3] and its copolymer with 3-hydroxyvalerate (PHBV) [4][5][6]. Other biodegradable plastics used for denitrification are poly(ε-caprolactone) (PCL) [7][8][9][10][11], poly(butylene succinate) (PBS) [12], and poly(L-lactic acid) (PLLA) [13][14][15][16]. Nevertheless, the SPD process is yet to be applied for practical use as a plant-scale system.…”