Search Results (4)

Partial nitrification–anaerobic ammonia oxidation represents an innovative nitrogen removal technique, distinguished by its shortened nitrogen removal pathway and reduced energy demands. Currently, partial nitrification is mostly studied in sequential batch reactors, and some of the methods to realize partial nitrification in continuous flow reactors have problems such as complicated operation and management, and can be easily destabilized. This study introduces a novel system utilizing light to establish an algal-bacterial consortium within a partial nitrification framework, where oxygen is supplied by algae and a novel rotating biological contactor (RBC). This approach aims to simplify the control strategy and decrease the energy required for aeration. The results demonstrated that light at an intensity of 200 μmol/(m²·s) effectively inhibited nitrite-oxidizing bacteria (NOB), swiftly stabilizing partial nitrification. In the absence of light, free ammonia (FA) and free nitric acid (FNA) inhibited NOB, with ammonium removal efficiency (ARE) and nitrite accumulation ratio (NAR) at 68.35% and 34.00%, respectively. By day 88, under light exposure, effluent NO₂⁻-N concentrations surged, with ARE and NAR at 64.21% and 69.45%, respectively. By day 98, NAR peaked at 80.28%. The specific oxygen uptake rate (SOUR) of ammonia-oxidizing bacteria (AOB) and NOB outside the disc was 3.24 mg O₂/(g MLSS·h) and 0.75 mg O₂/(g MLSS·h), respectively. Extracellular polymeric substance (EPS) content initially decreased, then increased, ultimately exceeding pre-light exposure levels. Microbial abundance significantly declined due to light exposure, with Nitrosomonas related-AOB decreasing by 91.88% from 1.6% to 0.13%, and Nitrospira related-NOB decreasing by 99.23% from 5.19% to 0.04%, respectively. The results indicated that both AOB and NOB were inhibited by light, especially NOB. It is a feasible strategy to achieve partial nitrification and algal-bacterial consortia by using light in a rotating biological contactor. Full article

The redox balance of inorganic sulfur in heavily polluted rivers might be disrupted, making sulfur reduction a major metabolic pathway of sulfate-reducing bacteria (SRB), leading to a massive accumulation of S²⁻ and blackening the water bodies. A mixed culture microbial consortium (MCMC) of Citrobacter sp.sp1, Ochrobactrum sp.sp2, and Stenotrophomonas sp.sp3 was used to activate native sulfate-oxidizing bacteria (SOB) to augment the S²⁻ oxidizing process. The results demonstrated that MCMC had a significant sulfur oxidation effect, with 98% S²⁻ removal efficiency within 50 h. The sulfide species varied greatly and were all finally oxidized to SO₄²⁻. The mechanism of bio-augmentation was revealed through high throughput sequencing analysis. The MCMC could stimulate and simplify the community structure to cope with the sulfide change. The microorganisms (family level) including Enterococcaceae, Flavobacteriaceae, Comamonadaceae, Methylophilaceae, Caulobacteraceae, Rhodobacteraceae, and Burkholderiaceae were thought to be associated with sulfide metabolism through the significant microbial abundance difference in the bio-treatment group and control group. Further Pearson correlation analysis inferred the functions of different microorganisms: Comamonadaceae, Burkholderiaceae, Alcaligenaceae, Methylophilaceae, and Caulobacteraceae played important roles in S²⁻ oxidization and SO₄²⁻ accumulation; and Comamonadaceae, Burkholderiaceae, Alcaligenaceae, Methylophilaceae, Caulobacteraceae, Campylobacteraceae, Bacteriovoracaceae, and Rhodobacteraceae promoted the sulfur oxidation during the whole process. Full article

Kombucha is a fermented tea with a long history of production and consumption. It has been gaining popularity thanks to its refreshing taste and assumed beneficial properties. The microbial community responsible for tea fermentation—acetic acid bacteria (AAB), yeasts, and lactic acid bacteria (LAB)—is mainly found embedded in an extracellular cellulosic matrix located at the liquid–air interphase. To optimize the production process and investigate the contribution of individual strains, a collection of 26 unique strains was established from an artisanal-scale kombucha production; it included 13 AAB, 12 yeasts, and one LAB. Among these, distinctive strains, namely Novacetimonas hansenii T7SS-4G1, Brettanomyces bruxellensis T7SB-5W6, and Zygosaccharomyces parabailii T7SS-4W1, were used in mono- and co-culture fermentations. The monocultures highlighted important species-specific differences in the metabolism of sugars and organic acids, while binary co-cultures demonstrated the roles played by bacteria and yeasts in the production of cellulose and typical volatile acidity. Aroma complexity and sensory perception were comparable between reconstructed (with the three strains) and native microbial consortia. This study provided a broad picture of the strains’ metabolic signatures, facilitating the standardization of kombucha production in order to obtain a product with desired characteristics by modulating strains presence or abundance. Full article

The hydrothermal steam environment of Sasso Pisano (Italy) was selected to investigate the associated microbial community and its metabolic potential. In this context, 16S and 18S rRNA gene partial sequences of thermophilic prokaryotes and eukaryotes inhabiting hot springs and fumaroles as well as mesophilic microbes colonising soil and water were analysed by high-throughput amplicon sequencing. The eukaryotic and prokaryotic communities from hot environments clearly differ from reference microbial communities of colder soil sites, though Ktedonobacteria showed high abundances in various hot spring samples and a few soil samples. This indicates that the hydrothermal steam environments of Sasso Pisano represent not only a vast reservoir of thermophilic but also mesophilic members of this Chloroflexi class. Metabolic functional profiling revealed that the hot spring microbiome exhibits a higher capability to utilise methane and aromatic compounds and is more diverse in its sulphur and nitrogen metabolism than the mesophilic soil microbial consortium. In addition, heavy metal resistance-conferring genes were significantly more abundant in the hot spring microbiome. The eukaryotic diversity at a fumarole indicated high abundances of primary producers (unicellular red algae: Cyanidiales), consumers (Arthropoda: Collembola sp.), and endoparasite Apicomplexa (Gregarina sp.), which helps to hypothesise a simplified food web at this hot and extremely nutrient-deprived acidic environment. Full article