Algae Biofilm Reduces Microbe-Derived Dissolved Organic Nitrogen Discharges: Performance and Mechanisms

Abstract

Microbe-derived dissolved organic nitrogen (mDON) can readily induce harmful phytoplankton blooms, and thus, restricting its discharges is necessary. Recently, algae biofilm (AB) has attracted increasing interest for its advantages in nutrient recovery. However, its features in mDON control remain unexplored. Herein, AB's mDON formation and utilization performance, molecular characteristics, and metabolic traits have been investigated, with activated sludge (AS) as the benchmark for comparisons. Comparatively, AB reduced mDON formation by 83% when fed with DON-free wastewater. When fed with AS's effluent, it consumed at least 72% of the exogenous mDON and notably reduced the amount of protein/amino sugar-like compounds. Irrespective of the influent, AB ultimately produced more various unsaturated hydrocarbon and lignin analogues. Redundancy and network analysis highlighted the algal−bacterial synergistic effects exemplified by cross-feeding in reducing mDON concentrations and shaping mDON pools. Moreover, metagenomics-based metabolic reconstruction revealed that cyanobacteria Limnothrix and Kamptonema spp. facilitated mDON uptake, ammonification, and recycling, which supplied the extensive nitrogen assimilatory demand for amino acids, vitamins, and cofactors biosynthesis, and therefore promoted mDON scavenging. Our findings demonstrate that regardless of the secondary or tertiary process, cyanobacteria-dominated AB is promising to minimize bioavailable mDON discharges, which has implications for future eutrophication control.

Seasonal dynamics in picocyanobacterial abundance and clade composition at coastal and offshore stations in the Baltic Sea

“…This suggests that PE-SYN can benefit from newly fixed nitrogen, but the presence of N 2 -fixers is not a requirement to achieve peak abundances and thus other nitrogen pools should also be considered. The main nitrogen source for picocyanobacteria during the summer may be regeneration through ammonification 34 . This may be especially important in coastal and shallow water areas (< 50 m depth) where studies have estimated that it can represent up to 97% of the nitrogen requirements 33 , 78 .…”

“…Peak SYN cell abundances are normally recorded during periods of warm temperatures and low nutrient concentrations 8 , 30 . SYN cells may use ammonium (NH 4 ) from nitrogen (N 2 )-fixers or from regeneration through ammonification as main source of nitrogen 31 – 34 or can take up dissolved organic nitrogen (DON) directly 35 – 37 . Other nutrients such as phosphate (PO 4 ) have also been observed to have an effect on picocyanobacterial dynamics and distribution 38 .…”

Microbial Roles in Dissolved Organic Matter Transformation in Full-Scale Wastewater Treatment Processes Revealed by Reactomics and Comparative Genomics

“…Genome-centric metagenomics can unravel microbes’ metabolic potentials at species resolution. , Coupling the taxon-specific functional information of microbes and molecular traits of DOM provides the opportunity to correlate DOM molecules with microbial phylogeny and functionality. Besides, Yu et al recently introduced reactomics, which evaluates untargeted MS profiles at the reaction level.…”

Mass Flow and Metabolic Pathway of Nonaeration Greywater Treatment in an Oxygenic Microalgal–Bacterial Biofilm

“…In general, the functional enzymes continuously increased as the HRT was lowered from 28 to 6 h, but an HRT of 4 h led to declined abundances due to high LAS loading and biotoxicity. , The relatively low levels of ammonium monooxygenase subunit-A (amoA) and nitrous oxide reductase (nosZ) reinforced that N was mainly removed through assimilation by bacteria and microalgae, not N 2 emission via nitrification/denitrification (Figure ). Moreover, hydroxylamine reductase (hcp) in microalgae may have enabled N transformation and fixation . Most of the enzymes related to LAS biodegradation increased or remained stable with higher organic loading, a factor that enabled efficient LAS mineralization. , …”

“…A Venn diagram and α diversity estimation, as well as principal coordinate analysis (PCoA), redundancy analysis (RDA), and taxonomic classification, were achieved using the “vegan” software package in R Studio . EnrichM (version 0.5.0) was applied for the identification of Kyoto Encyclopedia of Genes and Genomes (KEGG) functional orthologs (i.e., EC) . Reads were normalized per million total reads to indicate the relative abundances of functional genes …”