Effect of Polystyrene Microplastics on Rice Seed Germination and Antioxidant Enzyme Activity

The accumulation and distribution of microplastics (MPs) in agricultural soils, including rice fields, is well studied. However, only a few studies have investigated the uptake of MPs by rice plants and the consequential toxic effects of MPs under solid-phase culture conditions. Hence, in this study, we explored the effects of different concentrations of polystyrene MPs (PS-MPs, with a size of 200 nm) on rice seed germination, root growth, antioxidant enzyme activity, and transcriptome. PS-MPs exhibited no significant effect on the germination of rice seeds (p > 0.05). However, PS-MPs significantly promoted root length (10 mg L−1; p < 0.05), and significantly reduced antioxidant enzyme activity (1000 mg L−1; p < 0.05). Staining with 3,3-diaminobenzidine and nitrotetrazolium blue chloride further revealed significant accumulation of reactive oxygen species in the roots of rice treated with PS-MPs. In addition, transcriptome data analysis revealed that PS-MPs induce the expression of genes related to antioxidant enzyme activity in plant roots. Specifically, genes related to flavonoid and flavonol biosynthesis were upregulated, whereas those involved in linolenic acid and nitrogen metabolism were downregulated. These results enhance our understanding of the responses of agricultural crops to MP toxicity.

Assessment of bovine oocytes quality and their resistance to age-related changes after maturation in single-phase and two-phase culture systems

Existing approaches to in vitro maturation (IVM) of bovine oocytes do not take into account their specific demands during terminal phase of IVM including the need for increasing of their resistance to age-re-lated changes. In this work, we performed for the first time a comparative investigation of nuclear maturation and abnormal changes of MII chromosomes in bovine oocytes after their maturation in single-phase system and different two-phase systems and after the subsequent prolonged culture of the ova. When using the single-phase system, cumulus-oocyte complexes (COCs) were cultured for 24 h in the medium TCM 199 containing 10% fetal bovine serum (FBS), 10 μg/ml FSH, and 10 μg/ml luteinizing hormone (LH). In the two-phase system, oocytes matured in the same conditions for first 16 h and then in a new medium (TCM 199 containing 10% FBS (Control) or the same medium supplemented with 50 ng/ml progesterone) for the remaining 8 h of IVM. After maturation in the single-phase and the two-phase systems, a part of COCs were transferred to an aging medium (TCM 199 containing 10% FBS) and further cultured for 24 h. The state of the nuclear material (stage of meiosis and abnormal changes of MII chromosomes) in the matured and aged oocytes was assessed using cytogenetic analysis. The rate of oocytes being at the MII stage of meiosis after IVM in the single-phase and the two-phase systems was similar and amounted 82.7-86.3%. In addition, no effect of the culture system on the rate of MII oocytes with abnormal morphology of chromosomes was revealed. For the single-phase culture, this rate after the end of the IVM period was 32.2±0.5% and for the two-phase systems culture 38.5±4.0%. The prolonged culture of matured oocytes led to an increase the frequency of destructive changes in MII chromosomes to 56.9±2.9 and 68.4±3.0%, respectively. Progesterone in the IVM medium (during the last 8 hours) also did not effect on the rate of nuclear maturation, but reduced the rate of oocytes with abnormal changes in chromosomes: after IVM, as compared with the Control and the two-phase system; after 24-hours prolonged culture as compared to control (P <0.05). The results of the study suggest that the two-phase maturation of bovine oocytes may be used as an alternative to the conventional IVM protocol and that progesterone during the second phase of IVM causes an increase in the quality of ova and their resistance to subsequent age-related transformations.

Effect of Olive Mill Wastewaters on Scenedesmus Sp. Growth, Metabolism and Phenols Removal

Background The industry of olive oil produces large wastewater quantities. The elimination of these toxic by-products is an important environmental issue that requires a sufficient solution. In this study, Scenedesmus sp. was used for the simultaneous lipid and antioxidant molecules production and olive mill wastewater biodegradation.Results The two-stage olive mill wastewater cultivation did not significantly inhibit the production of microalgal biomass, compared to a single growth stage, when OMW and OMUF were supplied at the beginning of cultivation. OMUF, at 40%, enhanced the Ch a, b and carotenoids amounts (2.57, 7.4 and 1.69 mg/g dw, respectively), and protein and carbohydrate accumulation (350.96 and 315.62 ng/cell, respectively), after single phase culture. However, the highest OMUF and OMW concentrations increased total lipid content to 639. 13 and 679.86 ng/cell, respectively. About 58% of phenol removal was achieved and highest accumulation of polyphenols in algal cells with 40% OMUF condition under one stage strategy. The highest OMUF and OMW concentrations exhibited highest DPPH and ABTS scavenging ability after single and two-phase culture. Moreover, the cytotoxicity of the OMUF against HEK- 293 human embryonic kidney cells was evaluated by MTT assay. The MTT assay showed that the biomass of Scenedesmus sp. cultured on Tunisian filtered olive mill waste water did not shown any toxic effect.Conclusion Our results indicate that Scenedesmus sp. is a promising microalga for the biotreatment of OMW and the production of bioactive metabolites.