Microbial community distribution and genetic analysis in a sludge active treatment for a complex industrial wastewater: a study using microbiological and molecular analysis and principal component analysis

The isolation and identification of Bacillus velezensis ZN-S10 from vanilla (V. planifolia), and the microbial distribution after the curing process

The market value of vanilla beans (Vanilla planifolia) is constantly increasing due to their natural aroma and flavor properties that improve after a curing process, where bacteria colonization plays a critical role. However, a few publications suggest that bacteria play a role in the curing process. Hence, this study aimed to isolate Bacillus sp. that could be used for fermenting V. planifolia while analyzing their role in the curing process. Bacillus velezensis ZN-S10 identified with 16S rRNA sequencing was isolated from conventionally cured V. planifolia beans. A bacteria culture solution of B. velezensis ZN-S10 (1 mL of 1 × 107 CFU mL-1) was then coated on 1 kg of non-cured vanilla pods that was found to ferment and colonize vanilla. PCA results revealed distinguished bacterial communities of fermented vanilla and the control group, suggesting colonization of vanilla. Phylogenetic analysis showed that ZN-S10 was the dominant Bacillus genus member and narrowly correlated to B. velezensis EM-1 and B. velezensis PMC206-1, with 78% and 73% similarity, respectively. The bacterial taxonomic profiling of cured V. planifolia had a significant relative abundance of Firmicutes, Proteobacteria, Cyanobacteria, Planctomycetes, and Bacteroidetes phyla according to the predominance. Firmicutes accounted for 55% of the total bacterial sequences, suggesting their colonization and effective fermentation roles in curing vanilla.

Seasonal prevalence of bacteria in the outflow of two full-scale municipal wastewater treatment plants

Despite many modern wastewater treatment solutions, the most common is still the use of activated sludge (AS). Studies indicate that the microbial composition of AS is most often influenced by the raw sewage composition (especially influent ammonia), biological oxygen demand, the level of dissolved oxygen, technological solutions, as well as the temperature of wastewater related to seasonality. The available literature mainly refers to the relationship between AS parameters or the technology used and the composition of microorganisms in AS. However, there is a lack of data on the groups of microorganisms leaching into water bodies whose presence is a signal for possible changes in treatment technology. Moreover, sludge flocs in the outflow contain less extracellular substance (EPS) which interferes microbial identification. The novelty of this article concerns the identification and quantification of microorganisms in the AS and in the outflow by fluorescence in situ hybridization (FISH) method from two full-scale wastewater treatment plants (WWTPs) in terms of 4 key groups of microorganisms involved in the wastewater treatment process in the context of their potential technological usefulness. The results of the study showed that Nitrospirae, Chloroflexi and Ca. Accumulibacter phosphatis in treated wastewater reflect the trend in abundance of these bacteria in activated sludge. Increased abundance of betaproteobacterial ammonia-oxidizing bacteria and Nitrospirae in the outflow were observed in winter. Principal component analysis (PCA) showed that loadings obtained from abundance of bacteria in the outflow made larger contributions to the variance in the PC1 factorial axis, than loadings obtained from abundance of bacteria from activated sludge. PCA confirmed the reasonableness of conducting studies not only in the activated sludge, but also in the outflow to find correlations between technological problems and qualitative and quantitative changes in the outflow microorganisms.

Microbial Population Dynamics in Model Sewage Treatment Plants and the Fate and Effect of Gold Nanoparticles

Adequate functioning of a sewage treatment plant (STP) is essential to protect the downstream aquatic environment (ECHA 2017), and information on the degradability of chemicals and their toxicity to activated sludge microorganisms is required. An environmental realistic higher tier test is a STP simulation test as described in OECD 303A (2001) which for nanoparticles can also be used to study their sorption behavior to activated sludge. However, information is limited on the influence of synthetic sewage on the microbial community of the activated sludge. A modified community can result in modifications of the sludge floccules affecting the sorption behavior. The main objective of our study was to show whether a representative microbial diversity remains under standardized test conditions as described in OECD 303A (2001) using synthetic sewage as influent. Furthermore, we investigated whether just considering the functional properties of a STP (elimination of dissolved organic carbon; nitrification), is sufficient for an assessment of gold nanoparticles (AuNPs) or whether the influence on microbial diversity also needs to be considered. AuNPs were used as a case study due to their rising medical applications and therefore increasing probability to reach the sewer and STP. The results can provide significant input for the interpretation of results from the regulatory point of view. To deliver these objectives, the general changes of the microbial population in activated sludge and its influence on the degradation activity (dissolved organic carbon (DOC) and inorganic nitrogen) using freshly collected sludge from the municipal STP in an artificial test system as a model STP in accordance with OECD 303A (2001) were assessed. Additionally, we evaluated the potential impact of AuNPs and its dispersant on the microbial composition and the overall impact on the function of the STP in terms of DOC degradation and nitrogen removal to observe if an assessment based on functional properties is sufficient. The bacteria composition in our study, evaluated at a class level, revealed commonly described environmental bacteria. Proteobacteria (β, α, δ) accounted for more than 50% but also nitrifying bacteria as Nitrospira were present. Our results show that mainly within the first 7 days of an acclimatization phase by addition of synthetic sewage, the bacterial community changed. Even though AuNPs can have antibacterial properties, no adverse effects on the function and structure of the microorganisms in the STP could be detected at concentrations of increased modeled PEC values by a factor of about 10,000. Complementary to other metallic nanomaterials, gold nanomaterials also sorb to a large extent to the activated sludge. If activated sludge is used as fertilizer on agricultural land, gold nanoparticles can be introduced into soils. In this case, the effect on soil (micro)organisms must be investigated more closely, also taking into account the structural diversity.

Aerobic degradation and the effect of hexabromocyclododecane by soil microbial communities in Taiwan

Hexabromocyclododecane (HBCD) is one of the most frequently used brominated flame retardants (BFRs) in the industries nowadays. Despite being listed as persistent organic pollutant (POP), it is still in use until 2025. Because of its bio-accumulative and toxic characteristics, the applicable remediation approach is required. The aim of this study is to identify the microbial community from soil with HBCD degradation ability. The soil suspension and soil samples from Chiang Chun Soil and River Bank Soil showed to degrade HBCD by 60% 4 days after treatment, the debromination ratio was around 60%, and the total HBCD removal ratio reached 70% and 77.9%, respectively. The HBCD debromination metabolites, and oxidation metabolites were identified by GC-MS. The microbial taxonomic diversity was observed with DGGE approach to evaluate the effect of HBCD of microbial community. Bacillus spp. and Clostridium spp. were identified as the dominant microbes in the Chiang Chun Soil, but the amount of Bacillus spp. were showed to be affected by HBCD. In conclusion, HBCD could be removed by the microbial consortium in soil under aerobic culturing condition by various metabolic pathways.

Selection of a Very Active Microbial Community for the Coupled Treatment of Tetramethylammonium Hydroxide and Photoresist in Aqueous Solutions

Aerobic treatment of wastewater containing Tetramethylammonium hydroxide (TMAH) and photoresist was investigated using a lab scale reactor inoculated with activated sludge coming from urban wastewater treatment that never received TMAH before. The consumption of TMAH was monitored by liquid ion chromatography. Biodiversity indices were calculated from Denaturing Gradient Gel Electrophoresis (DGGE) bands distribution and used to estimate changes in community composition related to adaptation to the new feeding compound. The first week of adaptation was crucial, and it was analyzed in detail: many organisms died, and the microbial community suffered a great shock. TMAH levels remained constant through the first four days, and then suddenly dropped to undetectable, and at the same time NH₄⁺ increased. When the community showed complete adaptation, predominant groups of bacteria were obtained by the Illumina sequencing of 16s rDNA amplicons, to provide insights on ecology of the adapted community, focusing on the main actors of TMAH abatement. Richness of species (Rr) peaks suggest that the development of TMAH-consuming bacteria leads to persistent consortia that maintain toxicity resistance over time. This showed adaptation and changes of the population to the different feeding conditions, and it opens new perspectives in the in situ treatment of these important residues of industrial processes without relying on external processing plants.