Improved anaerobic sludge fermentation mediated by a tryptophan-degrading consortium: Effectiveness assessment and mechanism deciphering.

The hydrolysis of extracellular polymeric substances (EPS) represents a critical bottleneck in the anaerobic fermentation of waste activated sludge (WAS), while tryptophan is identified as an underestimated constituent of EPS. Herein, we harnessed a tryptophan-degrading microbial consortium (TDC) to enhance the hydrolysis efficiency of WAS. At TDC dosages of 5%, 10%, and 20%, a notable increase in SCOD was observed by factors of 1.13, 1.39, and 1.88, respectively. The introduction of TDC improved both the yield and quality of short chain fatty acids (SCFAs), the maximum SCFA yield increased from 590.6 to 1820.2, 1957.9 and 2194.9 mg COD/L, whilst the acetate ratio within SCFAs was raised from 34.1% to 61.2-70.9%. Furthermore, as TDC dosage increased, the relative activity of protease exhibited significant increments, reaching 116.3%, 168.0%, and 266.1%, respectively. This enhancement facilitated WAS solubilization and the release of organic substances from bound EPS into soluble EPS. Microbial analysis identified Tetrasphaera and Soehngenia as key participants in WAS solubilization and the breakdown of protein fraction. Metabolic analysis revealed that TDC triggered the secretion of enzymes associated with amino acid metabolism and fatty acid biosynthesis, thereby fostering the decomposition of proteins and production of SCFAs.

Simultaneous partial nitrification, denitrification, and phosphorus removal in sequencing batch reactors via controlled reduced aeration and short-term sludge retention time decrease.

Simultaneous bio-treatment processes of organic carbon (C)-, nitrogen (N)-, and phosphorus (P)-containing wastewater are challenged by insufficient carbon sources in the effluent. In the present study, two parallel anaerobic/aerobic sequencing batch reactors (R-1 and R-2) treating low C/N (≤4) wastewater were employed using different partial nitrification start-up strategies, controlled reduced aeration, and decreased sludge retention time. Advanced removal efficiencies for NH4+-N (≥96%), total nitrogen (TN, ≥86%), PO43--P (≥95%), and CODintra (≥91%) were realized, with TN and PO43--P effluent concentrations of 10.0 ± 3.5 and 0.11 ± 0.3 mg/L in R-1 and 9.28 ± 4.0 and 0.11 ± 0.1 mg/L in R-2, respectively. Higher nitrite accumulation rate (nearly 100%) and TN (121.1 ± 0.7 mg TN/g VSS·d) and P (12.5 ± 0.6 mg PO43--P/g VSS·d) removal loadings were obtained in R-2 by a thorough elimination of nitrite-oxidizing bacteria. Moreover, different microbial structures and nutrient removal pathways were identified. Denitrifying glycogen-accumulating organisms (Candidatus Competibacter) and phosphorus-accumulating organisms (PAOs) (Tetrasphaera) removed N and P with partial nitrification-endogenous denitrification pathways and aerobic P removal in R-1. In R-2, aerobic denitrifying bacteria (Psychrobacter) and PAOs ensured N and P removal through the partial nitrification-aerobic denitrification and aerobic P removal pathways. Compared to R-1, R-2 offers greater efficiency, convenience, and scope to further reduce carbon-source demand.

Agromyces mangrovi sp. nov., a Novel Actinobacterium Isolated from Mangrove Soil.

A novel, Gram-stain-positive, microaerophilic to aerobic, non-endospore-forming, no-motile and rod-shaped bacterium designated Q14T was isolated from mangrove soil samples collected on chengmai, Hainan province, China. Strain Q14T was able to grow at 10-40 °C (optimum 30 °C), pH 5.5-10.0 (optimum 6.5-8.0) and with 0.5-6% (w/v) NaCl (optimum 1%). The genomic DNA G+C content was 70.1%. The chemotaxonomic analysis showed that the predominant isoprenoid quinone was MK-12 and the major fatty acids were anteiso-C15:0, iso-C17:0 and anteiso-C17:0. The major polar lipids of strain Q14T were diphosphatidylglycerol, phosphatidylglycerol and one glycolipid. The strain Q14T contained 2,4-diaminobutylic acid (A2bu), alanine acid, glutamic acid and glycine in the peptidoglycans. The phylogenetic analysis and DNA-DNA hybridization, along with the phenotypic and chemotaxonomic characteristics, indicate that strain Q14T as a novel species of the genus Agromyces, for which the name Agromyces mangrovi sp. nov. is proposed. The type strain is Q14T (= MCCC 1K03191T = KCTC 39814T).