Enhancing biomass and lipid accumulation by a novel microalga for unsterilized piggery biogas slurry remediation.

The cost and efficiency of an algal-BS treatment system are determined by the specific microalgal species and BS pretreatment method. This study examines the growth of a novel algae Chlorella sp. YSD-2 and the removal of nutrients from the BS using different pretreatment methods, including dilution ratio and sterilization. The highest biomass production (1.84 g L-1) was achieved in the 1:2 unsterilized biogas slurry, which was 2.03 times higher than that in the sterilized group, as well as higher lipid productivity (17.29 mg L-1 d-1). Nevertheless, the sterilized biogas slurry at a 1:1 dilution ratio exhibited the most notable nutrient-removal efficiency, with COD at 71.97%, TP at 91.32%, and TN at 88.80%. Additionally, the analysis of 16S rRNA sequencing revealed a significant alteration in the indigenous bacterial composition of the biogas slurry by microalgal treatment, with Proteobacteria and Cyanobacteria emerging as the predominant phyla, and unidentified_Cyanobacteria as the primary genus. These findings suggest that Chlorella sp. YSD-2 exhibits favorable tolerance and nutrient-removal capabilities in unsterilized, high-strength biogas slurry, along with high productivity of biomass and lipids. Consequently, these results offer a theoretical foundation for the development of an efficient and economically viable treatment method for algal-BS.

Decolorization and detoxification of Brilliant Crocein GR by a newly enriched thermophilic consortium.

The environmental pollution caused by azo dyes at high temperatures has become an urgent problem. However, little attention has been paid to decolorizing azo dyes by thermophilic consortiums. In this study, a thermophilic bacterial consortium (BCGR-T) mainly composed of two genera, namely, Caldibacillus (70.90%) and Aeribacillus (17.63%) was first enriched, which can decolorize Brilliant Crocein GR (BCGR) at high temperatures (50-75 °C), pH values of 6∼8, dye concentrations (100-400 mg/L) and salinities (1-5%, w/v). The enzyme activity results showed that the azoreductase activity was nearly 8.8 times that of the control (p < 0.01), and the intracellular lignin peroxidase was also highly expressed with enzyme activity of 5.64 U (min-1 mg-1 protein) (p < 0.05), indicated that both azoreductase and intracellular lignin peroxidase played an important part in the decolorization process. Furthermore, seven new intermediate metabolic products, including aniline, phthalic acid, 2-carboxy benzaldehyde, phenylacetic acid, benzoic acid, toluene, and 4-methyl-hexanoic acid, were identified. In addition, functional genes related with the azo dye decolorization, such as those encoding the azoreductase, laccase, FMN reductase, NADPH-/NADH-quinone oxidoreductases and NADPH-/NADH dehydrogenases, catechol dioxygenase, homogentisate 1,2-dioxygenase, protocatechuate 3,4-dioxygenase, gentisate 1,2-dioxygenase, azobenzene reductase, naphthalene 1,2-dioxygenase, benzoate/toluate 1,2-dioxygenase, and anthranilate 1,2-dioxygenase and so on were found in the metagenome of the consortium BCGR-T. Finally, a new decolorization pathway of the thermophilic consortium BCGR-T was proposed. In addition, the phototoxicity of BCGR decreased after decolorization. Overall, the thermophilic consortium BCGR-T could be a promising candidate in the treatment of high concentration azo dye wastewater at high temperatures.

Distribution of the new functional marker gene (pahE) of aerobic polycyclic aromatic hydrocarbon (PAHs) degrading bacteria in different ecosystems.

Understanding the degradation potentials in PAHs-contaminated sites is significant for formulating effective bioremediation strategies. pahE encoding PAHs hydratase-aldolase has been proven as a better new functional marker gene of aerobic PAHs-degrading bacteria to assess the biodegradation potential of indigenous PAHs-degrading bacterial population. However, the distribution of pahE and its relationship with environmental factors remain unknown. The present study observed spatial variations in the diversity and abundance of pahE across oilfield soils, mangrove sediments, and urban roadside soils. nahE from Pseudomonas, bphE from Hyphomonas oceanitis, nagE from Comamonas testosterone, and novel pahE genes were widely present in these PAHs-polluted ecosystems. The abundance of pahE in PAHs-contaminated sites was in the range of 105-106 copies·g-1 (dry weight). Redundancy analysis and Pearson's correlation analysis implied that the distribution of pahE in the PAHs-contaminated environment was mainly shaped by environmental factors such as PAHs pollution level, nutrient level, salinity, and water content. This work was the first to explore the distribution of the new functional marker gene (pahE) and its links with environmental parameters, which provided new insights into the ecophysiology and distribution of indigenous aerobic PAHs-degrading bacteria in contaminated sites.

Recent Advances of Biochar-Based Electrochemical Sensors and Biosensors.

In the context of accelerating the global realization of carbon peaking and carbon neutralization, biochar produced from biomass feedstock via a pyrolysis process has been more and more focused on by people from various fields. Biochar is a carbon-rich material with good properties that could be used as a carrier, a catalyst, and an absorbent. Such properties have made biochar a good candidate as a base material in the fabrication of electrochemical sensors or biosensors, like carbon nanotube and graphene. However, the study of the applications of biochar in electrochemical sensing technology is just beginning; there are still many challenges to be conquered. In order to better carry out this research, we reviewed almost all of the recent papers published in the past 5 years on biochar-based electrochemical sensors and biosensors. This review is different from the previously published review papers, in which the types of biomass feedstock, the preparation methods, and the characteristics of biochar were mainly discussed. First, the role of biochar in the fabrication of electrochemical sensors and biosensors is summarized. Then, the analytes determined by means of biochar-based electrochemical sensors and biosensors are discussed. Finally, the perspectives and challenges in applying biochar in electrochemical sensors and biosensors are provided.

Shifts of the new functional marker gene (pahE) of polycyclic aromatic hydrocarbons (PAHs) degrading bacterial population and its relationship with PAHs biodegradation.

Identification of polycyclic aromatic hydrocarbons (PAHs) degrading bacterial populations and understanding their responses to PAHs are crucial for the designing of appropriate bioremediation strategies. In this study, the responses of PAHs-degrading bacterial populations to different PAHs were studied in terms of the compositions and abundance variations of their new functional marker gene (pahE) by gene-targeted metagenomic and qPCR analysis. Overall, PAHs species significantly affected the composition and abundance of pahE gene within the PAHs-degrading bacteria in each treatment and different pahE of PAHs-degrading bacteria involved in the different stages of PAHs degradation. Noted that new pahE genotypes were also discovered in all PAHs treatment groups, indicating that some potential new PAHs-degrading bacterial genera were also involved in PAHs degradation. Besides, all three PAH removal rates were significantly positively related with pahE gene abundances (R2 = 0.908 ~ 0.922, p < 0.01), demonstrating that pahE could be a good indicator of PAHs degradation activity or potential. This is the first study focusing on the dynamic changes of the pahE gene within PAHs-degrading bacterial community during the degradation of PAHs in mangrove sediment, providing novel insights into the use of pahE gene as the functional marker to indicate PAH degradation.

Enhanced anaerobic digestion of swine manure via a coupled microbial electrolysis cell.

Microbial electrolysis cell coupled anaerobic digestion (MEC-AD) is a new technology in energy recovery and waste treatment, which could be used to recycle swine manure. Here, different applied voltage effects were studied using MEC-AD with swine manure as a substrate. The maximum cumulative biogas and methane yields, both occurring with 0.9 V, were 547.3 mL/g total solid (TS) and 347.7 mL/g TS, respectively. The increased energy can counterbalance the electrical input. First order, logistic, gompertz, and back-propagation artificial neural network (BP-ANN) models were used to study cumulative biogas and methane yields. The BP-ANN model was superior to the other three models. The maximum degradation rate of hemicellulose, cellulose, and lignin was 60.97%, 48.59%, and 31.59% at 0.9 V, respectively. The BP-ANN model establishes a model for cumulative biogas and methane yields using MEC-AD. Thus, MEC-AD enhanced biogas and methane production and accelerated substrate degradation at a suitable voltage.

Molecular characterization of methanogenic microbial communities for degrading various types of polycyclic aromatic hydrocarbon.

Knowledge on methanogenic microbial communities associated with the degradation of polycyclic aromatic hydrocarbons (PAHs) is crucial to developing strategies for PAHs bioremediation. In this study, the linkage between the type of PAHs and microbial community structure was fully investigated through 16S rRNA gene sequencing on four PAH-degrading cultures. Putative degradation products were also detected. Our results indicated that naphthalene (Nap)/2-methylnaphthalene (2-Nap), phenanthrene (Phe) and anthracene (Ant) sculpted different microbial communities. Among them, Nap and 2-Nap selected for similar degrading bacteria (i.e., Alicycliphilus and Thauera) and methanogens (Methanomethylovorans and Methanobacterium). Nap and 2-Nap were probably activated via carboxylation, producing 2-naphthoic acid. In contrast, Phe and Ant shaped different bacterial and archaeal communities, with Arcobacter and Acinetobacter being Phe-degraders and Thiobacillus Ant-degrader. Methanogenic archaea Methanobacterium and Methanomethylovorans predominated Phe-degrading and Ant-degrading culture, respectively. These findings can improve our understanding of natural PAHs attenuation and provide some guidance for PAHs bioremediation in methanogenic environment.

Distribution of bacterial polycyclic aromatic hydrocarbon (PAH) ring-hydroxylating dioxygenases genes in oilfield soils and mangrove sediments explored by gene-targeted metagenomics.

PAH ring-hydroxylating dioxygenases (PAH-RHDα) gene, a useful biomarker for PAH-degrading bacteria, has been widely used to examine PAH-degrading bacterial community in different contaminated sites. However, the distribution of PAH-RHDα genes in oilfield soils and mangrove sediments and their relationship with environmental factors still remain largely unclear. In this study, gene-targeted metagenomics was first used to investigate the diversity of PAH-degrading bacterial communities in oilfield soils and mangrove sediments. The results showed that higher diversity of PAH-degrading bacteria in the studied samples was revealed by gene-targeted metagenomics than traditional clone library analysis. Pseudomonas, Burkholderia, Ralstonia, Polymorphum gilvum, Mycobacterium, Sciscionella marina, Rhodococcus, and potential new degraders were prevailed in the oilfield area. For mangrove sediments, novel PAH degraders and Mycobacterium were predominated. The spatial distribution of PAH-RHDα gene was dependent on geographical location and regulated by local environmental variables. PAH content played a key role in shaping PAH-degrading bacterial communities in the studied samples, which would enrich PAH-degrading bacterial population and decrease PAH-degrading bacterial diversity. This work brings a more comprehensive and some new insights into the distribution and biodegradation potential of PAH-degrading bacteria in soil and sediments ecosystems.

pahE, a Functional Marker Gene for Polycyclic Aromatic Hydrocarbon-Degrading Bacteria.

The characterization of native polycyclic aromatic hydrocarbon (PAH)-degrading bacteria is significant for understanding the PAH degradation process in the natural environment and developing effective remediation technologies. Most previous investigations of PAH-degrading bacteria in environmental samples employ pahAc, which encodes the α-subunit of PAH ring-hydroxylating dioxygenase, as a functional marker gene. However, the poor phylogenetic resolution and nonspecificity of pahAc result in a misestimation of PAH-degrading bacteria. Here, we propose a PAH hydratase-aldolase-encoding gene, pahE, as a superior biomarker for PAH-degrading bacteria. Comparative phylogenetic analysis of the key enzymes involved in the upper pathway of PAH degradation indicated that pahE evolved dependently from a common ancestor. A phylogenetic tree constructed based on PahE is largely congruent with PahAc-based phylogenies, except for the dispersion of several clades of other non-PAH-degrading aromatic hydrocarbon dioxygenases present in the PahAc tree. Analysis of pure strains by PCR confirmed that pahE can specifically distinguish PAH-degrading bacteria, while pahAc cannot. Illumina sequencing of pahE and pahAc amplicons showed more genotypes and higher specificity and resolution for pahE Novel reads were also discovered among the pahE amplicons, suggesting the presence of novel PAH-degrading populations. These results suggest that pahE is a more powerful biomarker for exploring the ecological role and degradation potential of PAH-degrading bacteria in ecosystems, which is significant to the bioremediation of PAH pollution and environmental microbial ecology.IMPORTANCE PAH contamination has become a worldwide environmental issue because of the potential toxic effects on natural ecosystems and human health. Biotransformation and biodegradation are considered the main natural elimination forms of PAHs from contaminated sites. Therefore, the knowledge of the degradation potential of the microbial community in contaminated sites is crucial for PAH pollution bioremediation. However, the nonspecificity of pahAc as a functional marker of PAH-degrading bacteria has resulted neither in a reliable prediction of PAH degradation potential nor an accurate assessment of degradation. Here, we introduced pahE encoding the PAH hydratase-aldolase as a new and better functional marker gene of PAH-degrading bacteria. This study provides a powerful molecular tool to more effectively explore the ecological role and degradation potential of PAH-degrading bacteria in ecosystems, which is significant to the bioremediation of PAH pollution.