Bioaugmentation of Thauera mechernichensis TL1 for enhanced polyhydroxyalkanoate production in mixed microbial consortia for wastewater treatment.

Polyhydroxyalkanoate (PHA) is a fully biodegradable bioplastic. To foster a circular economy, the integration of PHA production into wastewater treatment facilities can be accomplished using mixed microbial consortia. The effectiveness of this approach relies greatly on the enrichment of PHA-accumulating microorganisms. Hence, our study focused on bioaugmenting Thauera mechernichensis TL1 into mixed microbial consortia with the aim of enriching PHA-accumulating microorganisms and enhancing PHA production. Three sequencing batch reactors-SBRctrl, SBR2.5%, and SBR25%-were operated under feast/famine conditions. SBR2.5% and SBR25% were bioaugmented with T. mechernichensis TL1 at 2.5%w/w of mixed liquor volatile suspended solids (MLVSS) and 25%w/w MLVSS, respectively, while SBRctrl was not bioaugmented. SBR2.5% and SBR25% achieved maximum PHA accumulation capacities of 56.3 %gPHA/g mixed liquor suspended solids (MLSS) and 50.2 %gPHA/gMLSS, respectively, which were higher than the 25.4 %gPHA/gMLSS achieved by SBRctrl. The results of quantitative polymerase chain reaction targeting the 16S rRNA gene specific to T. mechernichensis showed higher abundances of T. mechernichensis in SBR2.5% and SBR25% compared with SBRctrl in the 3rd, 17th, and 31st cycles. Fluorescence in situ hybridization, together with fluorescent staining of PHA with Nile blue A, confirmed PHA accumulation in Thauera spp. The study demonstrated that bioaugmentation of T. mechernichensis TL1 at 2.5%w/w MLVSS is an effective strategy to enhance PHA accumulation and facilitate the enrichment of PHA-accumulating microorganisms in mixed microbial consortia. The findings could contribute to the advancement of PHA production from wastewater, enabling the transformation of wastewater treatment plants into water and resource recovery facilities.

Valorization of food waste derived anaerobic digestate into polyhydroxyalkanoate (PHA) using Thauera mechernichensis TL1.

Polyhydroxyalkanoate (PHA) is a biopolymer that can be used as a bioplastic, offering a green alternative to petroleum-based plastics. In this study, we investigated PHA production using Thauera mechernichensis TL1. The optimal molar C/N ratio was determined to be 20 from among the ratios of 4, 20, 40, 80, and 200 and in the absence of nitrogen. Food waste anaerobic digestate, mainly comprised of acetate and propionate, was used as the carbon source for PHA production by T. mechernichensis TL1, resulting in a maximum PHA content of 23.98 ± 0.52 wt% (0.52 ± 0.02 g/L PHA) with a PHA productivity of 0.043 g/L-h PHA. In addition, when using acetate and propionate, T. mechernichensis TL1 produced PHA with a maximum PHA content of 57.43 ± 2.84 wt% (2.04 ± 0.11 g/L PHA) and 50.94 ± 1.61 wt% (2.62 ± 0.16 g/L PHA), with a PHA productivity of 0.092 g/L-h PHA and 0.070 g/L-h PHA, respectively. Proton nuclear magnetic resonance spectroscopy (1H NMR) confirmed polyhydroxybutyrate (PHB) production using acetate as a carbon source, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) production using propionate or food waste anaerobic digestate as the carbon source. The whole-genome analysis of T. mechernichensis TL1 confirmed the existence of a PHA biosynthesis pathway, with the presence of phaA, phaB, phaC (Class I and Class II), and phaJ genes. This study was the first to demonstrate Thauera sp.'s ability to produce PHA from food waste anaerobic digestate, rendering it as a promising candidate for PHA-producing bacteria for the valorization of food waste.

Chitosan nanoparticle immersion vaccine offers protection against tilapia lake virus in laboratory and field studies.

Tilapia lake virus (TiLV), an enveloped negative-sense single-stranded RNA virus, causes tilapia lake virus disease (TiLVD), which is associated with mass mortality and severe economic impacts in wild and farmed tilapia industries worldwide. In this study, we developed a chitosan nanoparticle TiLV immersion vaccine and assessed the efficacy of the vaccine in laboratory and field trials. Transmission electron microscopy showed that the inactivated vaccine had a particle size of 210.3 nm, while the nano inactivated vaccine had a spherical shape with a diameter of 120.4 nm. Further analysis using fluorescent staining and immunohistochemistry analysis revealed the mucoadhesive properties of the nanovaccine (CN-KV) through fish gills. We assessed the efficacy of an immersion-based TiLV nanovaccine using a cohabitation challenge model. The fish that received the nanovaccine showed better relative percent survival (RPS) at 68.17% compared with the RPS of the inactivated virus vaccine (KV) group at 25.01%. The CN-KV group also showed a higher TiLV-specific antibody response than the control and KV groups (p < 0.05). Importantly, under field conditions, the fish receiving the CN-KV nanovaccine had better RPS at 52.2% than the nonvaccinated control group. Taken together, the CN-KV nanovaccinated fish showed better survival and antibody response than the control and KV groups both under laboratory control challenge conditions and field trials. The newly developed immersion-based nanovaccine is easy to administer in small fish, is less labor-intensive, and allows for mass vaccination to protect fish from TiLV infection.

Comparative genomic analyses of pathogenic bacteria and viruses and antimicrobial resistance genes in an urban transportation canal.

Water commuting is a major urban transportation method in Thailand. However, urban boat commuters risk exposure to microbially contaminated bioaerosols or splash. We aimed to investigate the microbial community structures, identify bacterial and viral pathogens, and assess the abundance of antimicrobial resistance genes (ARGs) using next-generation sequencing (NGS) at 10 sampling sites along an 18 km transportation boat route in the Saen Saep Canal, which traverses cultural, commercial, and suburban land-based zones. The shotgun metagenomic (Illumina HiSeq) and 16S rRNA gene amplicon (V4 region) (Illumina MiSeq) sequencing platforms revealed diverse microbial clusters aligned with the zones, with explicit segregation between the cultural and suburban sites. The shotgun metagenomic sequencing further identified bacterial and viral pathogens, and ARGs. The predominant bacterial pathogens (>0.5 % relative abundance) were the Burkholderia cepacia complex, Arcobacter butzleri, Burkholderia vietnamiensis, Klebsiella pneumoniae, and the Enterobacter cloacae complex. The viruses (0.28 %-0.67 % abundance in all microbial sequences) comprised mainly vertebrate viruses and bacteriophages, with encephalomyocarditis virus (33.3 %-58.2 % abundance in viral sequences), hepatitis C virus genotype 1, human alphaherpesvirus 1, and human betaherpesvirus 6A among the human viral pathogens. The 15 ARG types contained 611 ARG subtypes, including those resistant to beta-lactam, which was the most diverse and abundant group (206 subtypes; 17.0 %-27.5 %), aminoglycoside (94 subtypes; 9.6 %-15.3 %), tetracycline (80 subtypes; 15.6 %-20.2 %), and macrolide (79 subtypes; 14.5 %-32.1 %). Interestingly, the abundance of ARGs associated with resistance to beta-lactam, trimethoprim, and sulphonamide, as well as A. butzleri and crAssphage, at the cultural sites was significantly different from the other sites (p < 0.05). We demonstrated the benefits of using NGS to deliver insights into microbial communities, and antimicrobial resistance, both of which pose a risk to human health. Using NGS may facilitate microbial risk mitigation and management for urban water commuters and proximal residents.

Microbial community compositions and sulfate-reducing bacterial profiles in malodorous urban canal sediments.

Anthropogenically impacted urban canals represent distinct freshwater ecosystems that could shape microbial communities in underlying sediments; however, knowledge of the relationships between environmental factors and microbial community compositions and their functions in such an environment is limited. This study characterized the microbial community compositions of malodorous canal sediments at six locations along the Saen Saep Canal in Thailand. 16S rRNA gene amplicon sequencing (MiSeq, Illumina) revealed dominant genera classified as fermentative bacteria, methanogens, and sulfate-reducing bacteria (SRB), all of which emphasized anaerobic environments. SRB, as the primary producers of malodorous hydrogen sulfide, accounted for 8.2-30.4% of the total sequences. dsrB gene clone libraries further identified the SRB species. A constrained correspondence analysis demonstrated a spatial pattern of SRB that correlated with physicochemical parameters in which nitrate and sulfate in sediments were the most influencing factors. Overall, a better understanding of the SRB and other related microorganisms in canal sediments can assist in the future implementation of appropriate olfactory abatement and management methodologies in urban canals.

Identification of sulfate-reducing and methanogenic microbial taxa in anaerobic bioreactors from industrial wastewater treatment plants using next-generation sequencing and gene clone library analyses.

An understanding of microbial communities present in anaerobic bioreactors can strongly facilitate the development of approaches to control undesirable microorganisms, such as sulfate-reducing bacteria (SRB), in the system. In this study, overall microbial communities present in anaerobic bioreactors from seven industrial wastewater treatment plants (including food, pulp and paper industries) were investigated using 16S rRNA gene amplicon sequencing (MiSeq, Illumina). The dominant methanogens identified in the anaerobic bioreactors treating industrial wastewater were Methanobacterium and Methanosaeta; Methanospirillum was a predominant methanogen in the anaerobic sludge digester. Hydrogenotrophic and acetoclastic methanogens were detected at similar relative abundances in the anaerobic covered lagoons treating starch wastewater, whereas hydrogenotrophic methanogens were the predominant methanogens present in the sludge digester. SRB communities were further investigated using dsrB gene clone libraries. The results indicated the presence of SRB, such as uncultured Desulfobulbus sp., Syntrophobacter fumaroxidans, Syntrophorhabdus sp. PtaB.Bin027, and Desulfovibrio fructosivarans JJ. Incomplete-oxidizing SRB were the predominant SRB in all of the anaerobic bioreactors treating wastewater. In contrast, similar relative abundances of complete and incomplete-oxidizing SRB were observed in the sludge digester. The results of this study can further facilitate the development of SRB-controlling strategies to improve the efficiency of wastewater treatment.