Investigating flocculation mechanisms and ecological safety of cationic guar gum for rapid harvesting of microalgal cells.

Addressing the drawbacks of traditional flocculants on microalgae biomass harvesting is crucial for large-scale industrial applications of microalgae production. In this study, cationic bioflocculant was successfully prepared by introducing cationic groups into the side chain of guar gum, achieving in-situ algae flocculation efficiency of 83.5 % with the dosage of 18.0 mg/L under pH = 10.0. Through a harmonious integration of predictive modelling and practical experimentation, a superior cell flocculation capacity of 23.5 g/g was achieved. In addition, the environmental safety and biocompatibility of cationic guar gum was assessed, using the typical suspension quantitative bacteriostatic method and the fluorescent double-staining technique. The results showed that the inhibition efficiency of Staphylococcus aureus in the system containing 60.0 mg/L cationic guar gum was only 12.0 % and there was no inhibition against Escherichia coli colonies. These findings provide a safe and green flocculant for efficient microalgae harvesting and spent medium treatment.

Performance evaluation of typical flocculants for efficient harvesting of Chlorella sorokiniana under different carbon application modes.

In this study, the growth characteristics of microalgae cultured with different carbon sources were analyzed, and the flocculation characteristics under the influence of carbon sources were evaluated using three typical flocculants. The results showed that the organic carbon sources could significantly increase the content of extracellular proteins in microalgae. Specifically, the extracellular protein concentrations of microalgae cultured with pure BG-11, ethanol, sodium acetate and glucose were 18.2 29.2, 97.3, and 34.7 mg/g, respectively. During the flocculation process, microalgae cultured with sodium acetate exhibited a weak response to the flocculant because of excessive extracellular proteins inhibited flocculation. In addition, the flocculation efficiency was also less than 50.0% cultured with sodium acetate in all pH test ranges when alum and chitosan were used as flocculants. It could be inferred that the flocculant initially happened to charge neutralization with the negatively charged proteins in the solution and then bridged the charges with the microalgae. These findings provide insights into the effects of different carbon sources on microalgal flocculation, promising organic integration of microalgae wastewater treatment and harvesting.

Toxic responses of freshwater microalgae Chlorella sorokiniana due to exposure of flame retardants.

Flame retardants, such as Tetrabromobisphenol A (TBBPA), Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and tributyl phosphate (TBP), are frequently detected in surface water. However, the effects of FRs exposure on aquatic organisms especially freshwater microalgae are still unclear. In this study, the toxicities of TBBPA, TDCPP and TBP to microalgae Chlorella sorokiniana, in terms of growth inhibition, photosynthetic activity inhibition and oxidative damage, were investigated, and according ecological risks were assessed. The results showed that TBBPA, TDCPP and TBP had inhibitory effects on C. sorokiniana, with 96 h EC50 (concentration for 50% of maximal effect) values of 7.606, 41.794 and 49.996 mg/L, respectively. Fv/Fm decreased as the increase of exposure time under 15 mg/L TBBPA. Under 50 mg/L TDCPP and 80 mg/L TBP exposure, Fv/Fm decreased significantly after 24 h. However, Fv/Fm rose after 96 h, indicating that the damaged photosynthetic activity was reversible. The content of chlorophyll a decreased, as the increase of TBBPA concentration from 3 to 15 mg/L. However, chlorophyll a increased first and then decreased, as the increase of TDCPP and TBP concentrations from 0 to 50 mg/L and 0-80 mg/L, respectively. Results indicated that C. sorokiniana could use the phosphorus of TDCPP and TBP to ensure the production of chlorophyll a. The risen content of reactive oxygen species, malondialdehyde as well as superoxide dismutase activity indicated that exposure to FRs induced oxidative stress. Additionally, the risk quotients showed that tested FRs had ecological risks in natural waters or wastewaters. This study provides insights into the toxicological mechanisms of different FRs toward freshwater microalgae for better understanding of according environmental risks.

Towards advanced nutrient removal by microalgae-bacteria symbiosis system for wastewater treatment.

In this study, the microalgae-bacteria symbiosis (ABS) system by co-culturing Chlorella sorokiniana with activated sludge was constructed for pollutants removal, and the according interaction mechanism was investigated. The results showed that the ABS system could almost completely remove ammonia nitrogen, and the removal efficiency of total nitrogen and total phosphorus could accordingly reach up to 65.3 % and 42.6 %. Brevundimonas greatly promoted microalgal biomass growth (maximum chlorophyll-a concentration of 9.4 mg/L), and microalgae contributed to the increase in the abundance of Dokdonella and Thermomonas in ABS system, thus facilitating nitrogen removal. The extended Derjaguin-Landau-Verwey-Overbeek theory indicated a repulsive potential barrier of 561.7 KT, while tryptophan-like proteins and tyrosine-like proteins were key extracellular polymeric substances for the formation of flocs by microalgae and activated sludge. These findings provide an in-depth understanding of interaction mechanism between microalgae and activated sludge for the removal of contaminants from wastewater.

Nutrient removal and lipid production by the co-cultivation of Chlorella vulgaris and Scenedesmus dimorphus in landfill leachate diluted with recycled harvesting water.

Applying microalgae for landfill leachate (LL) treatment is promising. However, LL usually needs to be diluted with much fresh water, aggravating water shortage. In this study, mono- and co-culturing microalgae (Chlorella vulgaris and Scenedesmus dimorphus) were used to treat LL diluted with recycled harvesting water, to investigate nutrient removal and lipid production. The results showed that microalgae in co-culture treatment had more biomass and stronger superoxide dismutase activity, which might be related to humic acids contained in recycled harvesting water, according to dissolved organic matters (DOMs) analysis. In addition, the lipid content and yield of co-cultured microalgae reached 27.60 % and 66.87 mg·L-1, respectively, higher than those of mono-culture, proving the potential of co-culture for the improvement of lipid production. This study provided a freshwater-saving dilution method for LL treatment with recycled harvesting water as well as a strategy for the increase of biomass and lipid accumulation by microalgae co-cultivation.

Responses of microalgae under different physiological phases to struvite as a buffering nutrient source for biomass and lipid production.

Microalgae cultivation for biodiesel production is promising, but the high demand for nutrients, such as nitrogen and phosphorus, remains a limiting factor. This study investigated effects of struvite, a low-cost nutrient source, on microalgae production under different physiological phases. Changes in element concentrations were determined to characterize the controllable nutrient release properties of struvite. Results showed that nutrient elements could be effectively supplemented by struvite. However, responses of microalgae under different growth stages to struvite varied obviously, achieving the highest biomass (0.53 g/L) and the lowest (0.32 g/L). Moreover, the microalgal lipid production was obviously increased by adding struvite during the growth phase, providing the first evidence that struvite could serve as an alternative buffering nutrient source to culture microalgae. The integration of microalgae cultivation with struvite as a buffering nutrient source provides a novel strategy for high ammonia nitrogen wastewater treatment with microalgae for biodiesel production.

Microalgal cultivation for the upgraded biogas by removing CO2, coupled with the treatment of slurry from anaerobic digestion: A review.

Biogas is the gaseous by product generated from anaerobic digestion (AD), which is mainly composed of methane and CO2. Numerous independent studies have suggested that microalgae cultivation could achieve high efficiency for nutrient uptake or CO2 capture from AD, respectively. However, there is no comprehensive review on the purifying slurry from AD and simultaneously upgrading biogas via microalgal cultivation technology. This paper aims to fill this gap by presenting and discussing an information integration system based on microalgal technology. Furthermore, the review elaborates the mechanisms, configurations, and influencing factors of integrated system and analyzes the possible challenges for practical engineering applications and provides some feasibility suggestions eventually. There is hope that this review will offer a worthwhile and practical guideline to researchers, authorities and potential stakeholders, to promote this industry for sustainable development.

Biochar amendment of aerobic composting for the effective biodegradation of heavy oil and succession of bacterial community.

Soil pollution caused by petroleum pollutants from production trade activities in petroleum-related factories contributes serious threat to the environment and human health. Composting is technically-feasible and cost-effective in the biodegradation of heavy oil pollutants. This composting experiment was developed with four rice husk biochar (RHB) concentrations of 0 wt% (CK), 5 wt% (S1), 10 wt% (S2) and 15 wt% (S3) for the degradation of heavy oil. The results showed that RHB amendment could strengthen the degradation performance of heavy oil, and the degradation efficiencies for CK, S1, S2 and S3 were 59.67%, 65.00%, 73.29% and 74.82%, respectively. Microbial community succession process was investigated through high-throughput sequencing technology, and the RHB addition regulated bacterial community succession and further effectively facilitated the biodegradation of heavy oil in composting. This study substantiated that biochar materials-amended aerobic composting would be a promising strategy for the biodegradation of petroleum pollutants.

Heterogeneous nuclear ribonucleoprotein M promotes the progression of breast cancer by regulating the axin/ß-catenin signaling pathway.

Despite significant progress in the treatment of breast cancer due to advances in surgery, cytotoxic agents, and endocrine therapy, the prognosis for patients has not improved much. Accumulated evidence indicates that heterogeneous nuclear ribonucleoprotein M (hnRNPM) and Wnt/ß-catenin function as tumor oncogenes in the progression of many cancers. The present study aimed to explore whether HnRNPM/ß-catenin signaling molecules might serve as a genetic target for breast cancer treatment. To shed light on this issue, quantitative real-time polymerase chain reaction (qRT-PCR) detection, Western blotting, and immunohistochemical staining were performed. The hnRNPM is expressed at a much higher level in breast cancer tissues and cell lines than in noncancerous tissues and cell lines. In vitro studies revealed that overexpressed hnRNPM promoted cell proliferation and colony formation but inhibited cell apoptosis. In vivo results demonstrated that upregulation of hnRNPM dramatically increased breast cancer xenograft tumor growth. Western blotting and immunofluorescence studies revealed that hnRNPM markedly activated the Wnt/ß-catenin pathway and catalyzed its translocation from the cytoplasm to the nucleus by targeting axin, a negative regulator of Wnt/ß-catenin signaling in MCF-7 and KPL-4 cells. Elevated levels of c-Myc and cyclin D1 were observed when MCF-7 and KPL-4 cells were transfected with a hnRNPM vector. These findings indicate that the hnRNPM/axin/ß-catenin signaling pathway acts as an oncogenic promoter in the progression of breast cancer, suggesting that hnRNPM may be a potential target for the treatment of this disease.

Association between transforming growth factor-ß1 expression and the clinical features of triple negative breast cancer.

The aim of the present study was to investigate the association between the expression levels of transforming growth factor-ß1 (TGF-ß1) and the clinical pathological characteristics and prognosis of triple negative breast cancer (TNBC) through study of TNBC patient tissue samples. The biological effects of TGF-ß1 on TNBC cells and the potential signal transduction pathway are additoinally investigated. Immunohistochemistry was utilized to investigate expression changes of the positive rate of TGF-ß1 in the TNBC, compared with the non-TNBC group, to explain the association between TGF-ß1 and clinical pathological characteristics and prognosis. MDA-MB-231 cells were treated with TGF-ß1 and subsequently the invasion and migration abilities, and the expression of proteins in certain signaling pathways were assessed before and after the treatment. Positive expression of TGF-ß1 was observed in 52.5% of TNBC tissue samples, which was higher than that observed in non-TNBC group (27.5%). High levels of TGF-ß1 expression were not significantly associated age, menopausal status, family history of cancer or tumor size; however, tumor histological grade and axillary lymph node metastasis were significantly associated (P<0.05). In addition, when the TGF-ß1 expression levels are higher, the 5-year disease-free survival rate is lower. TGF-ß1 expression promoted the invasion and migration of MDA-MB-231 cells, and the expression of Smad2 protein and P38 protein was increased, indicating that Smad2 protein and the P38 signaling pathway may serve an important role in TNBC.