Assessment of Nitrate Removal Capacity of Two Selected Eukaryotic Green Microalgae

Eutrophication is a leading problem in water bodies all around the world in which nitrate is one of the major contributors. The present study was conducted to study the effects of various concentrations of nitrate on two eukaryotic green microalgae, Chlamydomonas sp. MACC-216 and Chlorella sp. MACC-360. For this purpose, both microalgae were grown in a modified tris-acetate-phosphate medium (TAP-M) with three different concentrations of sodium nitrate, i.e., 5 mM (TAP-M5), 10 mM (TAP-M10) and 15 mM (TAP-M15), for 6 days and it was observed that both microalgae were able to remove nitrate completely from the TAP-M5 medium. Total amount of pigments decreased with the increasing concentration of nitrate, whereas protein and carbohydrate contents remained unaffected. High nitrate concentration (15 mM) led to an increase in lipids in Chlamydomonas sp. MACC-216, but not in Chlorella sp. MACC-360. Furthermore, Chlamydomonas sp. MACC-216 and Chlorella sp. MACC-360 were cultivated for 6 days in synthetic wastewater (SWW) with varying concentrations of nitrate where both microalgae grew well and showed an adequate nitrate removal capacity.

Characterization and Biotechnological Potential of Two Native Marine Microalgae Isolated from the Tunisian Coast

Microalgae are attracting considerable interest worldwide. In the present study, two native microalgae strains isolated from Tunisian cost were identified as Chlamydomonas sp. and Navicula sp. We characterized their pigment and protein contents, as well as their carbohydrate and lipid productivity. The predominant fatty acids were found to be α-linolenic acid (C18:3n-3) and palmitoleic acid (C16:1n-7) for Chlamydomonas sp. and Navicula sp. strains respectively. Microalgae methanol extracts showed important in vitro antibacterial activity against all tested gram negative bacteria. Antioxidant activities of methanol extracts were investigated by determining radical scavenging activity according to DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) methods. MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay showed that the newly isolated microalgae were not toxic and have potential application in the fish feeds domain as a supplement in fish meal. Also, the biosorption of cadmium from aqueous solutions by microalgae living cells was evaluated. Large removal capacities were obtained with values ranging from 89.8% to 99.38%. These results are very promising as a starting point for a potential application of these new isolates for in situ bioremediation of heavy metals contaminating aqueous systems.

Environmental Factors Associated with the Eukaryotic Microbial Community and Microalgal Groups in the Mountain Marshes of South Korea

The diversity indices of eukaryotic microalgal groups in the Jeonglyeongchi, Waegok, and Wangdeungjae marshes of Mount Jiri, Korea, were measured using Illumina MiSeq and culture-based analyses. Waegok marsh had the highest species richness, with a Chao1 value of 828.00, and the highest levels of species diversity, with Shannon and Simpson index values of 6.36 and 0.94, respectively, while Wangdeungjae marsh had the lowest values at 2.97 and 0.75, respectively. The predominant species in all communities were Phagocata sibirica (Jeonglyeongchi, 68.64%), Aedes albopictus (Waegok, 34.77%), Chaetonotus cf. (Waegok, 24.43%), Eimeria sp. (Wangdeungjae, 26.17%), and Eumonhystera cf. (Wangdeungjae, 22.27%). Relative abundances of the microalgal groups Bacillariophyta (diatoms) and Chlorophyta (green algae) in each marsh were respectively: Jeonglyeongchi 1.38% and 0.49%, Waegok 7.0% and 0.3%, and Wangdeungjae 10.41% and 4.72%. Illumina MiSeq analyses revealed 34 types of diatoms and 13 types of green algae. Only one diatom (Nitzschia dissipata) and five green algae (Neochloris sp., Chlamydomonas sp., Chlorococcum sp., Chlorella vulgaris, Scenedesmus sp.) were identified by a culture-based analysis. Thus, Illumina MiSeq analysis can be considered an efficient tool for analyzing microbial communities. Overall, our results described the environmental factors associated with geographically isolated mountain marshes and their respective microbial and microalgal communities.

Penilaian Sistem Suntikan Gas Biohidrogen Menerusi Tetapan Arduino menggunakan Kultur Mikroalga Tempatan melalui Kaedah Fermentasi Fotosintesis dan Gelap

Biohidrogen (gas hidrogen yang terhasil melalui kaedah biologi) ialah salah satu sumber tenaga mampan yang boleh diaplikasi untuk penjanaan elektrik. Hasil tindak balas pembakaran gas hidrogen menghasilkan air tanpa pelepasan gas rumah hijau. Mikroalga merupakan salah satu mikroorganisma yang boleh menghasilkan biohidrogen secara fermentasi fotosintesis dan gelap. Dalam kajian ini, mikroalga tempatan, Chlamydomonas sp. UKM6 telah digunakan untuk menghasilkan biohidrogen menggunakan kedua-dua kaedah fermentasi dalam keadaan anaerobik. Fermentasi fotosintesis dijalankan menggunakan kultur UKM6 yang hidup di bawah sinaran cahaya manakala fermentasi gelap dijalankan dengan menggunakan biojisim UKM6 yang diinokulasi dengan enapcemar daripada efluen kilang kelapa sawit (POME). Gas hidrogen yang terhasil disuntik secara automatik ke dalam sistem sel bahan api menggunakan Arduino Uno yang telah dibangunkan. Dengan menggunakan data yang dipaparkan daripada program tetapan Arduino, biojisim UKM6 dalam fermentasi gelap menghasilkan gas hidrogen dan nilai voltan purata tertinggi masing-masing pada kepekatan 30.89 ppm dan 0.92 mV. Berdasarkan keputusan yang diperoleh, dapat disimpulkan bahawa mikroalga berpotensi menjana tenaga melalui penghasilan biohidrogen yang dapat terus dianalisa menggunakan teknologi sel bahan api. Sistem ini jelas dapat dapat diperbaiki lagi pada masa akan datang untuk mengukur penjanaan tenaga secara terus dengan berkesan.

Constitutively Up-regulated Carbon Metabolism is an Adaptation to Low Temperature in the Antarctic Psychrophile Chlamydomonas sp. UWO241

The Antarctic alga Chlamydomonas sp. UWO241 is an obligate psychrophile that thrives in the cold but is unable to survive at moderate, seemingly innocuous temperatures. We dissect the responses of UWO241 to temperature stress using global metabolomic approaches. UWO241 exhibits slow growth at 4°C, a temperature closest to its natural habitat, and faster growth at higher temperatures of 10-15°C. We demonstrate that the slower growth-rate characteristic of UWO241 at 4⁰C is not necessarily a hallmark of stress. UWO241 constitutively accumulates high levels of protective metabolites including soluble sugars, polyamines and antioxidants at a range of steady-state temperatures. In contrast, the mesophile Chlamydomonas reinhardtii accumulates these metabolites only during cold stress. Despite low growth rates, 4°C-grown UWO241 cultures had a higher capacity to respond to heat stress (24°C) and accumulated increased amounts of antioxidants, lipids and soluble sugars, when compared to cultures grown at 10-15°C. We conclude that the slower growth rate and the unique psychrophilic physiological characteristic of UWO241 grown at 4⁰C result in a permanently re-routed steady-state metabolism, which contributes to its increased resistance to heat stress. Our work adds to the growing body of research on temperature stress in psychrophiles, many of which are threatened by climate change.

Species-specific response of phytoplankton to zooplankton grazing in tropical eutrophic reservoirs

Aim To test the hypothesis that zooplankton changes the structure of phytoplankton in tropical reservoirs by reducing the biomass of algal species susceptible to herbivory. Methods We experimentally evaluated the species-specific responses of phytoplankton to zooplankton within eutrophic reservoirs with different phytoplankton community structure in northeastern of Brazil. Water samples were collected from the subsurface in coastal regions of the Apipucos and Mundaú reservoirs in January/2012 and November/2014, respectively, and transported to the laboratory. The experiments were performed in Erlenmeyer flasks (1 liter) filled with water from the sample sites and were maintained for five days in the laboratory conditions. Two treatments were maintained (1) with phytoplankton and the presence of the native zooplankton and (2) without native zooplankton. Results Zooplankton proved to be an important factor, modifying the structure of the phytoplankton community, especially in the Apipucos reservoir. In this reservoir, we observed a significant reduction of biomass in diatom Cyclotella meneghiniana, and the chlorophyte Chlamydomonas sp., and an increase in the biomass of Raphidiopsis raciborskii. In the Mundaú reservoir, we observed a significant reduction of C. meneghiniana and R. raciborskii, while cyanobacteria Microcystis aeruginosa increased their biomasses in the presence of zooplankton. Conclusions These results show the importance of the microalgae community structure in phytoplankton-zooplankton interactions for food webs in tropical environments, as well as support the role of zooplankton in fostering cyanobacterial growth and maintain algal blooms.