Ultrasonic-assisted extraction of total flavonoids from Zanthoxylum bungeanum residue and their allelopathic mechanism on Microcystis aeruginosa.

Water eutrophication has emerged as a pressing concern for massive algal blooms, and these harmful blooms can potentially generate harmful toxins, which can detrimentally impact the aquatic environment and human health. Consequently, it is imperative to identify a safe and efficient approach to combat algal blooms to safeguard the ecological safety of water. This study aimed to investigate the procedure for extracting total flavonoids from Z. bungeanum residue and assess its antioxidant properties. The most favorable parameters for extracting total flavonoids from Z. bungeanum residue were a liquid-solid ratio (LSR) of 20 mL/g, a solvent concentration of 60%, an extraction period of 55 min, and an ultrasonic temperature of 80 °C. Meanwhile, the photosynthetic inhibitory mechanism of Z. bungeanum residue extracts against M. aeruginosa was assessed with a particular focus on the concentration-dependent toxicity effect. Z. bungeanum residue extracts damaged the oxygen-evolving complex structure, influenced energy capture and distribution, and inhibited the electron transport of PSII in M. aeruginosa. Furthermore, the enhanced capacity for ROS detoxification enables treated cells to sustain their photosynthetic activity. The findings of this study hold considerable relevance for the ecological management community and offer potential avenues for the practical utilization of resources in controlling algal blooms.

Development of chemically defined media for Lactococcus lactis subsp. lactis YF11 to eliminate the influence of hyperosmotic stress.

Chemically defined media (CDM) can eliminate or lessen the interference that occurs in complex culture media (CCM) caused by the undefined substrate pools, and various CDM have been designed and employed for investigating microbial physiology and multiomics. Herein, using the measured amount of total amino acids in CCM and combined with the in vivo and in vitro amino acid content of Lactococcus lactis subsp. lactis YF11, new enriched CDM were designed and then optimized using a statistical design-of-experiment method coupling with fed-batch fermentation to eliminate or lessen the influence of hyperosmotic pressure. Cell volume was introduced as a target index to assess the performance of CDM, and average osmotic pressure (AOP) was employed to describe the osmotic pressure of CDM. The AOP was significantly decreased from 610 mOsm/kg·H2O in the initial CDM (I-CDM) to 360 mOsm/kg·H2O in fed-batch CDM (F-CDM), and the cell volume was increased from 0.142 ± 0.004 µm3 in I-CDM to 0.198 ± 0.008 µm3 in F-CDM, which was close to 0.206 ± 0.005 µm3 found in CCM, indicating that the strategy of designing and improving CDM followed by a statistical design-of-experiment coupling with fed-batch cultivation presented a promising pathway for extensive utilization of CDM. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03788-5.

Variations in bacterial diversity and community structure in the sediments of an alkaline lake in Inner Mongolia plateau, China.

Alkaline lakes are a special aquatic ecosystem that act as important water and alkali resource in the arid-semiarid regions. The primary aim of the study is to explore how environmental factors affect community diversity and structure, and to find whether there are key microbes that can indicate changes in environmental factors in alkaline lakes. Therefore, four sediment samples (S1, S2, S3, and S4) were collected from Hamatai Lake which is an important alkali resource in Ordos' desert plateau of Inner Mongolia. Samples were collected along the salinity and alkalinity gradients and bacterial community compositions were investigated by Illumina Miseq sequencing. The results revealed that the diversity and richness of bacterial community decreased with increasing alkalinity (pH) and salinity, and bacterial community structure was obviously different for the relatively light alkaline and hyposaline samples (LAHO; pH < 8.5; salinity < 20‰) and high alkaline and hypersaline samples (HAHR; pH > 8.5; salinity > 20‰). Firmicutes, Proteobacteria and Bacteriodetes were observed to be the dominant phyla. Furthermore, Acidobacteria, Actinobacteria, and low salt-tolerant alkaliphilic nitrifying taxa were mainly distributed in S1 with LAHO characteristic. Firmicutes, Clostridia, Gammaproteobacteria, salt-tolerant alkaliphilic denitrifying taxa, haloalkaliphilic sulfur cycling taxa were mainly distributed in S2, S3 and S4, and were well adapted to haloalkaline conditions. Correlation analysis revealed that the community diversity (operational taxonomic unit numbers and/or Shannon index) and richness (Chao1) were significantly positively correlated with ammonium nitrogen (r = 0.654, p < 0.05; r = 0.680, p < 0.05) and negatively correlated with pH (r = -0.924, p < 0.01; r = -0.800, p < 0.01; r = -0.933, p < 0.01) and salinity (r = -0.615, p < 0.05; r = -0.647, p < 0.05). A redundancy analysis and variation partitioning analysis revealed that pH (explanation degrees of 53.5%, pseudo-F = 11.5, p < 0.01), TOC/TN (24.8%, pseudo-F = 10.3, p < 0.05) and salinity (9.2%, pseudo-F = 9.5, p < 0.05) were the most significant factors that caused the variations in bacterial community structure. The results suggested that alkalinity, nutrient salt and salinity jointly affect bacterial diversity and community structure, in which one taxon (Acidobacteria), six taxa (Cyanobacteria, Nitrosomonadaceae, Nitrospira, Bacillus, Lactococcus and Halomonas) and five taxa (Desulfonatronobacter, Dethiobacter, Desulfurivibrio, Thioalkalivibrio and Halorhodospira) are related to carbon, nitrogen and sulfur cycles, respectively. Classes Clostridia and Gammaproteobacteria might indicate changes of saline-alkali conditions in the sediments of alkaline lakes in desert plateau.

Transcriptome analysis of lipid metabolism in response to cerium stress in the oleaginous microalga Nannochloropsis oculata.

Nannochloropsis oculata can accumulate large amounts of lipids under rare earth element (REE) conditions. However, the lipid accumulation mechanism responsible for REE stress has not been elucidated. In this study, the effects of cerium (the most abundant REE) on the growth and lipid accumulation of N. oculata were investigated. The de novo transcriptome data of N. oculata under cerium conditions were subsequently collected and analyzed. The results showed that N. oculata exhibited good cerium-resistance ability, showed slightly decrease in biomass but significantly increase in lipid content (55.8 % dry cell weight) under 6.0 mg/L cerium condition. Meanwhile, about 83.4 % cerium was biological fixated. Through transcriptome analysis, we found that the inhibited photosynthesis and carbon fixation pathways coupled with the stress-sensitive expression of ribosome biogenesis genes acclimatized the cells to REE stress. The active glycolysis pathway accelerated carbon flux to pyruvate and acetyl-CoA, and the upregulation of glycerol kinase and phosphatidate cytidylyltransferase genes further induced lipid accumulation. In addition, cerium downregulated the acyl-CoA oxidase and triacylglycerol lipase genes, which inhibited the degradation of lipids. Therefore, different responses to cerium demonstrate how N. oculata cells adapt to REE stress, and this knowledge may be used to extend our understanding of triacylglycerol (TAG) and the synthesis of other important metabolites.

The effect of NaCl stress on photosynthetic efficiency and lipid production in freshwater microalga-Scenedesmus obliquus XJ002.

Rapid industrialization and population growth have increased the world's energy demands, resulting in a shortage of conventional fossil fuels. Thus, there is an urgent need to develop sustainable and renewable forms of energy. Microalgae have emerged as a potential feedstock for biofuel production. Under stress conditions, lipid production is enhanced in algal cells due to changes in the lipid biosynthetic pathways that produce neutral lipids. In this study, we examined the physiological and biochemical effects of salinity stress (0.00, 0.01, 0.10, 0.15, 0.20M) on the freshwater microalga Scenedesmus obliquus XJ002. We found that the biomass and the content of chlorophyll a, b and carotenoids decreased with increasing NaCl concentration. NaCl stress damaged the oxygen evolving complex (OEC) and the PSII (photosystem II) reaction center and subsequently suppressed electron transport at the donor and receptor sides of the reaction center, influencing the absorption, transfer, and application of light energy. Additionally, the total lipid content of cells was significantly increased under NaCl stress treatment. The highest lipid content (32.26%) was found in cells cultured in the presence of 0.20M NaCl, which was about 2.52-fold higher than that of cells grown in medium lacking NaCl (12.82%). In addition to providing insight into the physiological and biochemical responses of S. obliquus XJ002 to salinity stress, these findings show that lipid production, and hence biofuel feedstock production, can be boosted by adjusting salt levels in the growth medium.

Application of an integrated biomarker response index to assess ground water contamination in the vicinity of a rare earth mine tailings site.

We utilized a multi-biomarker approach (Integrated Biomarker Response version 2, IBRv2) to investigate the scope and dispersion of groundwater contamination surrounding a rare earth mine tailings impoundment. Parameters of SD rat included in our IBRv2 analyses were glutathione levels, superoxide dismutase, catalase, and glutathione peroxidase activities, total anti-oxidative capacity, chromosome aberration, and micronucleus formation. The concentration of 20 pollutants including Cl(-), SO4 (2-), Na(+), K(+), Mg(2+), Ca(2+), TH, CODMn, As, Se, TDS, Be, Mn, Co, Ni, Cu, Zn, Mo, Cd, and Pb in the groundwater were also analyzed. The results of this study indicated that groundwater polluted by tailings impoundment leakage exhibited significant ecotoxicological effects. The selected biomarkers responded sensitively to groundwater pollution. Analyses showed a significant relationship between IBRv2 values and the Nemerow composite index. IBRv2 could serve as a sensitive ecotoxicological diagnosis method for assessing groundwater contamination in the vicinity of rare earth mine tailings. According to the trend of IBRv2 value and Nemerow composite index, the maximum diffusion distance of groundwater pollutants from rare earth mine tailings was approximately 5.7 km.