Single-cell sorting of microalgae and identification of optimal conditions by using response surface methodology coupled with life-cycle approaches

Exploration for cobalt/nitrogen-doped catalyst to creatinine degradation via peroxymonosulfate activation: toxicity evaluation, statistical modeling, and mechanisms study

Developing multifunctional catalysts applied in diversiform modes via advanced oxidation processes (AOPs) is a promising and attractive approach for organic pollution degradation. Herein, a novel hollow bamboo-like structural cobalt/nitrogen-doped carbonized material (CoC/N) was employed as a catalyst for AOPs, in which CoC/N was prepared in situ through calcining a Co-based coordination polymer. When CoC/N was utilized as a peroxymonosulfate (PMS) activator, the catalyst stood out prominent activities for effective CA oxidation. Furthermore, a five-level central composite rotatable design (CCRD) model describing CA decay as a function of PMS concentration, CoC/N dosage, and solution pH value was successfully constructed and engaged to explore the optimal operating conditions. Finally, the possible degradation mechanism of CA in CoC/N-PMS system was proposed by quantum chemistry calculation and LC/MS analysis. This work shed light on the structural morphology of the catalyst and its PMS synergy degradation pathway, which promotes its applications in miscellaneous pollutant degradation. A new Co/N-doped material was used to degrade unconventionality organic pollutant creatinine (CA) for the first time, in which the scientific approaches of five-level central composite rotatable design (CCRD) model, response surface methodology (RSM) and density function theory (DFT) were employed to evaluate the material performance and CA degradation pathway. The toxicity evaluation, statistical modeling and mechanisms study have been investigated meticulously.

Microalgae-based constructed wetland system enhances nitrogen removal and reduce carbon emissions: Performance and mechanisms

Combination of constructed wetlands (CWs) and microalgae-based technologies has been proved as effective wastewater treatment option; however, little attention was paid to investigate the optimal combination ways. This study showed that the integrated system (IS) connecting microalgal pond with CWs exhibited improved pollutant-removal efficiencies and preferred carbon reduction effects compared to other alternatives such as coupled system or independent CWs. Microbial analysis demonstrated that core microorganisms (e.g., Acinetobacter and Thermomonas) of the IS were mostly associated with carbon, nitrogen, and energy metabolism. Based on co-occurrence networks, microbial quantity with denitrification function in the IS accounted for 71.01 % of the microorganism related to nitrogen metabolism, which was higher than that of 48.84 % in the independent CWs, indicating that the presence of microalgae in IS played important role in promoting biological denitrification. These findings provide insights into the microbial mechanism and highlights the complementary effects between microalgae and CWs.

Exploring the resilience of constructed wetlands to harmful algal blooms disturbances: A study on microbial response mechanisms

Constructed wetlands (CWs) have emerged as a promising environmentally sustainable technique for wastewater treatment. However, the susceptibility of CWs to disturbances caused by harmful algal blooms (HABs) raises concerns. This study aimed to investigate the impact of HABs on the pollutants' removal performance of CWs and the response of rhizosphere microbial community. Results revealed that CWs possessed an adaptive capacity that enabled them to recover caused by HABs. The rhizosphere was found to stimulate the occurrence of Acinetobacter, which played a critical role to help resist HABs disturbance. This study also observed an increased dissimilatory nitrate reduction metabolic pathway which promoted denitrification and enhanced the nitrogen removal efficiency of CWs. Additionally, the structural equation model further suggested that dissolved oxygen exerted a significant influence on the microbial activities and then affected the pollutants removal performance. Overall, our findings shed light on the mechanism for CW stability maintenance during HABs disturbance.

Succession dynamics of microbial communities responding to the exogenous microalgae ZM-5 and analysis of the environmental sustainability of a constructed wetland system

Constructed wetlands (CWs) are economical and effective swine tailwater treatment systems. However, nitrogen removal in CWs is limited by the lack of carbon source for denitrification. In this study, we studied the feasibility of dosing the microalgae ZM-5 to improve the nitrogen removal ability in CWs. Compared to the control CW, a 20 % higher removal capacity of COD and TN was observed for the coupled system (EG). The microalgae ZM-5 could interact with denitrifying bacteria to compensate for the deficiency of denitrifying stage in CWs. HT-qPCR chip analysis also provided evidence that denitrification genes significantly increased (p < 0.05). According to the life cycle assessment (LCA), ultrasonic extraction had the best environmental sustainability among four lipid extraction processes. As an improvement strategy, clean energy could be utilized to optimize the electricity source to reduce environmental load (45 %-60 %). These findings offer new insights into the feasibility of EG for environmentally sustainable wastewater treatment.

Optimized Protocol for Microalgae DNA Staining with SYTO9/SYBR Green I, Based on Flow Cytometry and RSM Methodology: Experimental Design, Impacts and Validation

Multiple fluorochromes are extensively used to investigate different microalgal aspects, such as viability and physiology. Some of them can be used to stain nucleic acids (DNA). Well-known examples are SYBR Green I and SYTO 9, the latter of which offers several advantages, especially when combined with flow cytometry (FCM)—a powerful method for studying microalgal population heterogeneity and analyzing their cell cycles. However, the effects of these dyes on the microalgae cell physiology have not been fully elucidated yet. A statistical experimental design, using response surface methodology (RSM) with FCM was applied in this study to optimize the DNA staining of a non-conventional microalgae, Chromochloris zofingiensis, with SYBR Green I and SYTO 9, and to optimize the variables affecting staining efficiency, i.e., the dye concentration, incubation time and staining temperature. We found that none of these factors affects the staining efficiency, which was not less than 99.65%. However, for both dyes, the dye concentration was shown to be the most significant factor causing cell damage (p-values: 0.0003; <0.0001) for SYBR Green I and SYTO 9, respectively. The staining temperature was only significant for SYTO 9 (p-value: 0.0082), and no significant effect was observed regarding the incubation time for both dyes. The values of the optimized parameters (0.5 µM, 05 min and 25 °C) for SYTO 9 and (0.5 X, 5 min and 25 °C) for SYBR Green I resulted in the maximum staining efficiency (99.8%; 99.6%), and the minimum damaging effects (12.86%; 13.75%) for SYTO 9 and SYBR Green I, respectively. These results offer new perspectives for improving the use of DNA staining fluorochromes and provides insights into their possible side effects on microalgae.

Biphenyl-degrading Bacteria Isolation with Laser Induced Visualized Ejection Separation Technology and Traditional Colony Sorting

In this work, biphenyl was used as carbon source to enrich microorganisms from polychlorinated biphenyls (PCBs)-contaminated paddy soil samples, and the taxonomic structures in both of the soil samples and the fourth-generation enrichments were examined with high-throughput sequencing. Single cells were isolated from the enrichments via single cell sorting technology named Laser Induced Visualized Ejection Separation Technology (LIVEST) and also traditional single colony sorting, and the genera of the isolates were identified using 16S rRNA sequencing. The results from high-throughput sequencing present that enrichment from generation to generation can considerably change the microbial community. Comparing the two sorting methods, the LIVEST is more time-saving and cell-targeted for microbial resource exploration. Based on the further verification of biphenyl degradation, it was found that some strains belonging to genera Macrococcus, Aerococcus and Metabacillus are capable in degrading biphenyl, which have not been reported yet.