Effects of polystyrene nanoplastics on the physiological and biochemical characteristics of microalga Scenedesmusquadricauda

The contamination of the aquatic environment with microplastics has become a global environmental concern. Microplastic particles can be shredded to form smaller nanoplastics, and knowledge on their impacts on phytoplankton, especially freshwater microalgae, is still limited. To investigate this issue, the microalga Scenedesmus quadricauda was exposed to polystyrene nanoplastics (PS-NPs) of five concentrations (10, 25, 50, 100, and 200 mg/L). The growth; the contents of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD); the chlorophyll content; and concentrations of soluble protein and soluble polysaccharide were accordingly measured. The results showed that the microalgal density increased with the increase of the polystyrene nanoplastic concentrations, and the physiological features of alga were enhanced after the stimulation of nanoplastics. Furthermore, a high concentration (200 mg/L) of nanoplastics increased the contents of chlorophyll, soluble protein, and polysaccharide (P < 0.05). The antioxidant enzyme activities of Scenedesmus quadricauda were significantly activated by nanoplastics. Lastly, we propose three possible algal recovery mechanisms in response to nanoplastics in which Scenedesmus quadricauda was tolerant with PS-NPs by cell wall thickening, internalization, and aggregation. The results of this study contribute to understanding of the ecological risks of nanoplastics on freshwater microalgae.

Comparison of the transcriptomes of different life history stages of the freshwater Rhodophyte Thorea hispida

Thorea hispida exclusively inhabits freshwater environments and is characterized by a triphasic life history. In this study, the organelle genomes and transcriptomes of different life history stages of T. hispida were examined using next generation sequencing. The chloroplast and mitochondrial genomes of the chantransia stage were 175,747 and 25,411 bp in length, respectively. The chantransia stage was highly similar to the gametophyte stage based on comparisons of organelle genomes and phylogenetic reconstruction. Transcriptomic comparisons of two stages found that ribosome-related genes were the most up-regulated in the gametophyte stage of T. hispida. Seven meiosis-specific genes, including SPO11 initiator of meiotic double-stranded breaks(spo11), meiotic nuclear divisions 1(mnd1), RAD51 recombinase(rad51), mutS homolog 4(msh4), mutS homolog 5(msh5), REC8 meiotic recombination protein(rec8), and DNA helicase Mer3(mer3), were differentially regulated between the two life history stages. The organelle genomes and transcriptomes from T. hispida provided in this study will be valuable for future studies of freshwater red algae.

Effect of thermosonication process on physicochemical properties and microbial load of goat's milk

In this study, thermosonication was used as a combined treatment of raw goat milk (RGM) using pasteurization (72 °C for 15 s) and ultrasound treatments (20 kHz at the power variance of 150 W, 200 W, 300 W and 400 W for 10 min). Investigation on the impact of the microbial load, protein content, protein aggregation, the particle size of fat and casein micelles, pH, viscosity, turbidity, color, and soluble calcium and phosphorus contents were carried out, whiles RGM and PGM served as the control. Our results revealed that at 400 W, that thermosonication resulted in a significant reduction (α = 0.05) in the microbial load of the samples to less than 2.3 log cfu/mL in comparison to those of RGM and pasteurized goat milk (PGM) at 5.94 log cfu/mL and 4.76 log cfu/mL respectively. In RGM, the fat size (3.5 µm) decreased to 0.4 µm at 300 W; while those of casein micelles also decreased from 406 to 256.4 nm at 400 W. However, no significant effect was observed in the color and soluble calcium and phosphorus contents of all samples. The effect on the microbial load and fat homogenization would promote thermosonication process in the dairy industry.

Long term spatial-temporal dynamics of fluoride in sources of drinking water and associated health risks in a semiarid region of Northern China

There is a concern about the increasing prevalence of health problems related to the ingestion of fluoride (F^-) in the developing world. Drinking water is one important source of F^-, and the concentration of F^- needs to be known to ensure the safety of drinking water. In this study, F^- levels in drinking water were investigated across Taiyuan in Shanxi Province, China. Spatial-temporal distribution characteristics and potential associated health risks were analyzed using GIS. We collected 485 samples from shallow wells without any defluoridation treatments between 2008 and 2016. After analyzing the samples of F^- content we found that mean F^- levels of urban areas (0.61 ± 0.39 mg L^-1), suburban areas (0.70 ± 0.87 mg L^-1) and for all of Taiyuan city (0.63 ± 0.56 mg L^-1) were in optimum range based on the recommendation by USEPA. However, individual locations within industrial areas (e.g. Gujiao District) had higher F^- levels (1.06 mg L^-1). A concerning result showed that 12.37% of tested locations had F^- concentrations larger than 1.0 mg L^-1. We calculated F^- Health Risk Indices (HRIs_F) and found that highest were associated with suburban areas, especially in the year 2009 and 2010. However, from 2008 to 2016, overall F^- levels and HRIs_F of the sampled groundwater in Taiyuan City showed a decreasing trend. HRIs_F in suburban areas was higher than urban areas, possible due to the heavily prevalent coal mining industry in those areas. Specific policies should be formulated to address HRIs_F.

Application of Phragmites australis to remove phenol from aqueous solutions by chemical activation in batch and fixed-bed columns

The ability of the agricultural residue of Phragmites australis to serve as an absorbent material used to remove phenol from aqueous solutions in batch and continuous fixed-bed columns was investigated. Prepared adsorbents were characterized by SEM, FTIR, and pHpzc methods. The equilibrium adsorption (qe) of phenol was increased from 9.61 to 29.40 mg/g when the initial phenol concentrations increased from 50 to 150 mg/L. The max adsorption capacity of Phragmites australis was found to be 29.60 mg/g at 30 °C. In column studies, a higher flow rate, higher initial concentration of phenol, and shorter packing layer height increase the column adsorption capacity of phenol. In a batch and continuous fixed-bed column studies, the experiment data was evaluated by some classic models. Fitting degree between the experimental results shows that the pseudo-second-order adsorption kinetics and Langmuir model were the best. Thomas and Yoon-Nelson models were in good agreement with the experimental breakthrough curve data. Both batch and continuous investigation indicated that Phragmites australis could be used as a fine adsorbent to remove phenol and that the adsorption efficiency improved significantly in the column experiment.

Effects of gamma radiation on microbial, physicochemical, and structural properties of whey protein model system

Gamma radiation has been used in food processing for many years, though it has certain effects on food components. Whey protein solutions (10%/30%, wt/vol) were treated with gamma radiation at various dosages (10-25 kGy) and evaluated for microbial changes in the solutions and physicochemical and structural changes of whey proteins. Whey protein solutions after gamma radiation showed substantially lower populations of all viable microorganisms than those of controls. The 10% whey protein solution treated at radiation of 20 or 25 kGy remained sterile for up to 4 wk at room temperature. Gamma radiation increased viscosity and turbidity and decreased soluble nitrogen of whey protein solutions compared to nonradiated control samples regardless of radiation dosage. Nonreducing sodium dodecyl sulfate-PAGE suggested that whey proteins under gamma radiation treatment formed aggregates with high molecular weights. Reducing sodium dodecyl sulfate-PAGE showed that disulfide bonds played a role in gamma radiation-induced whey protein cross-linking. Scanning and transmission electron microscopy micrographs exhibited large aggregates of whey proteins after gamma radiation treatment. Results suggested that gamma radiation could be applied to whey protein solution for purposes of reducing microbial counts and cross-linking protein molecules.

Effect of high-doses pyrogallol on oxidative damage, transcriptional responses and microcystins synthesis in Microcystis aeruginosa TY001 (Cyanobacteria)

Severe eutrophication and harmful cyanobacterial blooms of freshwater ecosystems is a persistent environmental topic in recent decades. Pyrogallol (polyphenol) was confirmed to exhibit one of the most intensive inhibitory effects on the Microcystis aeruginosa. In this study, the expression of genes, release of microcystins (MCs) and antioxidant system of pyrogallol on Microcystis aeruginosa TY001 were investigated. The results revealed that the expression of stress response genes (prx, ftsH, grpE and fabZ) and DNA repair genes (recA and gyrB) were up-regulated. Meanwhile, the antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activity, were increased, and the stress caused lipid peroxidation to occur and malondialdehyde (MDA) levels to change. Unexpectedly, the relative transcript abundance of microcystin synthesis genes (mcyB, mcyD and ntcA) and the contents of microcystins (MCs) significantly increased compared with the control in the culture medium. In conclusion, oxidative damage and DNA damage are the primary mechanisms for the allelopathic effect of pyrogallol on M. aeruginosa TY001.

Identification and Characterization of miRNAs in Chondrus crispus by High-Throughput Sequencing and Bioinformatics Analysis

Chondrus crispus, an economically and medicinally important red alga, is a medicinally active substance and important for anti-tumor research. In this study, 117 C. crispus miRNAs (108 conserved and 9 novel) were identified from 2,416,181 small-RNA reads using high-throughput sequencing and bioinformatics methods. According to the BLAST search against the miRBase database, these miRNAs belonged to 110 miRNA families. Sequence alignment combined with homology searching revealed both the conservation and diversity of predicted potential miRNA families in different plant species. Four and 19 randomly selected miRNAs were validated by northern blotting and stem-loop quantitative real-time reverse transcription polymerase chain reaction detection, respectively. The validation rates (75% and 94.7%) demonstrated that most of the identified miRNAs could be credible. A total of 160 potential target genes were predicted and functionally annotated by Gene Ontology analysis and Kyoto Encyclopedia of Genes and Genomes analysis. We also analyzed the interrelationship of miRNAs, miRNA-target genes and target genes in C. crispus by constructing a Cytoscape network. The 117 miRNAs identified in our study should supply large quantities of information that will be important for red algae small RNA research.