posted on 2021-11-10, 21:13authored byMenghan Wu, Xinning Liu, Huilei Xiong, Weiming Tu, Xiaoqiang Gong, Peng Yu, Yina Zou, Hui Wang
Polyhydroxyalkanoate (PHA) production
from wastes by mixed microbial
cultures has been developed into an integrated process to couple with
nitrate removal due to its economic and environmental benefits. However,
the anoxic conditions for denitrification result in low productivity
of PHA production due to the limited energy supply. In this work,
the fully aerobic feeding regime uncoupling carbon and nitrogen supply
was applied to enhance the culture enrichment and productivity while
being accompanied by nitrate removal. The enriched cultures showed
a nitrate assimilation rate of 2.35 ± 1.10 mg of NO3––N per gram of active biomass (Xa) per hour; meanwhile, the specific growth
rate (μXa, 0.019 ±
0.002 h–1) and biomass yield on PHA (YXa/PHA, 0.68 ± 0.15 g Xa/g PHA) were higher than those of a classic
anoxic process (μXa,
0.011 ± 0.001 h–1 and YXa/PHA, 0.38 ± 0.09 g Xa/g PHA). Furthermore, ammonia and oxygen were
confirmed to have significant impacts on regulating nitrate utilization
by directing nitrate flow to assimilatory nitrate use, aerobic denitrification,
or anoxic denitrification. Metagenome analysis revealed that the overall
function was mostly undertaken by Thauera aminoaromatica, and a nitrate metabolic model driven by PHAs was proposed. In summary,
these findings widened application scenarios for PHA production coupled
with nitrate removal.