In recent decades, a shift has been seen in the use of light-emitting diodes over incandescent lights and compact fluorescent lamps (CFL), which eventually led to an increase in wastes of electrical equipment (WEE), especially fluorescent lamps (FLs) and CFL light bulbs. These widely used CFL lights, and their wastes are good sources of rare earth elements (REEs), which are desirable in almost every modern technology. Increased demand for REEs and their irregular supply have exerted pressure on us to seek alternative sources that may fulfill this demand in an eco-friendly manner. Bio-removal of wastes containing REEs, and their recycling may be a solution to this problem and could balance environmental and economic benefits. To address this problem, the current study focuses on the use of the extremophilic red alga, Galdieria sulphuraria, for bioaccumulation/removal of REEs from hazardous industrial wastes of CFL bulbs and the physiological response of a synchronized culture of G. sulphuraria. A CFL acid extract significantly affected growth, photosynthetic pigments, quantum yield, and cell cycle progression of this alga. A synchronous culture was able to efficiently accumulate REEs from a CFL acid extract and efficiency was increased by including two phytohormones, i.e., 6-Benzylaminopurine (BAP - Cytokinin family) and 1-Naphthaleneacetic acid (NAA - Auxin family).

• Keywords
• Galdieria sulphuraria, Rhodophyta, bio-removal, compact fluorescent lamp, extremophile, industrial wastes, plant hormones,
• Publication type
• Journal Article MeSH

The freshwater green microalgae, Dictyosphaerium chlorelloides (CCALA 330), has the ability to produce extracellular polysaccharides (EPS). Conditions for optimum growth and EPS overproduction were determined in laboratory-scale tubular photobioreactors (PBR) with a working volume of 300 mL. Multiple limitations in nutrient supply were proven to be an effective method for EPS overproduction. Salinity stress was also applied to the culture, but no significant increase in EPS production was observed. The effects of different nitrogen sources were examined and the microalgae exhibited the fastest growth and EPS production in medium containing ammonium nitrate. Under determined optimal conditions, EPS concentration reached 10 g/L (71% of the total biomass) and a total biomass of 14 g/L at the end of 17 days cultivation. Pilot-scale cultivation was also carried out in a column type airlift photobioreactor (PBR) with a working volume of 60 L. A new and efficient methodology was developed for separating cells from the EPS-containing culture broth. Due to the strong attachment between cells and EPS, high-pressure homogenization was carried out before a centrifugation process. The EPS in the supernatant was subsequently purified using ultrafiltration. The green microalgae Dictyosphaerium chlorelloides may therefore be appropriate for the commercial production of EPS.

• Keywords
• Dictyosphaerium chlorelloides, extracellular polysaccharides, photobioreactor,
• Publication type
• Journal Article MeSH

The aim of the study was to verify the hypothesis that a potential cause of the phytotoxicity of diclofenac (DCF, a non-steroidal anti-inflammatory drug) is an effect of cell cycle progression. This research was conducted using synchronous cultures of a model organism, green alga Chlamydomonas reinhardtii. The project examined DCF effects on selected parameters that characterize cell cycle progression, such as cell size, attainment of commitment points, DNA replication, number of nuclei formed during cells division and morphology of cells in consecutive stages of the cell cycle, together with the physiological and biochemical parameters of algae cells at different stages. We demonstrated that individual cell growth remained unaffected, whereas cell division was delayed in the DCF-treated groups grown in continuous light conditions, and the number of daughter cells from a single cell decreased. Thus, the cell cycle progression is a target affected by DCF, which has a similar anti-proliferative effect on mammalian cells.

• Keywords
• Chlamydomonas reinhardtii, cell cycle, diclofenac, non-steroidal anti-inflammatory drug,
• MeSH
• Anti-Inflammatory Agents, Non-Steroidal toxicity   MeSH
• Cell Division drug effects   MeSH
• Cell Cycle drug effects   MeSH
• Chlamydomonas reinhardtii drug effects   genetics   growth & development   MeSH
• Diclofenac toxicity   MeSH
• DNA, Plant biosynthesis   genetics   MeSH
• Photosynthesis drug effects   MeSH
• DNA Replication drug effects   MeSH
• Cell Size drug effects   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Anti-Inflammatory Agents, Non-Steroidal MeSH
• Diclofenac MeSH
• DNA, Plant MeSH

Green algae are fast-growing microorganisms that are considered promising for the production of starch and neutral lipids, and the chlorococcal green alga Parachlorella kessleri is a favorable model, as it can produce both starch and neutral lipids. P. kessleri commonly divides into more than two daughter cells by a specific mechanism-multiple fission. Here, we used synchronized cultures of the alga to study the effects of supra-optimal temperature. Synchronized cultures were grown at optimal (30 °C) and supra-optimal (40 °C) temperatures and incident light intensities of 110 and 500 μmol photons m-2 s-1. The time course of cell reproduction (DNA replication, cellular division), growth (total RNA, protein, cell dry matter, cell size), and synthesis of energy reserves (net starch, neutral lipid) was studied. At 40 °C, cell reproduction was arrested, but growth and accumulation of energy reserves continued; this led to the production of giant cells enriched in protein, starch, and neutral lipids. Furthermore, we examined whether the increased temperature could alleviate the effects of deuterated water on Parachlorella kessleri growth and division; results show that supra-optimal temperature can be used in algal biotechnology for the production of protein, (deuterated) starch, and neutral lipids.

• Keywords
• Parachlorella kessleri, cell cycle, deuterated lipid, deuterated starch, deuterium, energy reserves, growth processes, microalgae, reproduction events, starch, supra-optimal temperature,
• MeSH
• Biomass MeSH
• Cell Division physiology   MeSH
• Chlorophyta growth & development   MeSH
• Lipids MeSH
• Lipid Metabolism physiology   MeSH
• Microalgae metabolism   MeSH
• Starch metabolism   MeSH
• Temperature * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Lipids MeSH
• Starch MeSH

The extremophilic unicellular red microalga Galdieria sulphuraria (Cyanidiophyceae) is able to grow autotrophically, or mixo- and heterotrophically with 1% glycerol as a carbon source. The alga divides by multiple fission into more than two cells within one cell cycle. The optimal conditions of light, temperature and pH (500 µmol photons m-2 s-1, 40 °C, and pH 3; respectively) for the strain Galdieria sulphuraria (Galdieri) Merola 002 were determined as a basis for synchronization experiments. For synchronization, the specific light/dark cycle, 16/8 h was identified as the precondition for investigating the cell cycle. The alga was successfully synchronized and the cell cycle was evaluated. G. sulphuraria attained two commitment points with midpoints at 10 and 13 h of the cell cycle, leading to two nuclear divisions, followed subsequently by division into four daughter cells. The daughter cells stayed in the mother cell wall until the beginning of the next light phase, when they were released. Accumulation of glycogen throughout the cell cycle was also described. The findings presented here bring a new contribution to our general understanding of the cell cycle in cyanidialean red algae, and specifically of the biotechnologically important species G. sulphuraria.

• Keywords
• Galdieria, cell cycle, cell division, growth, light intensity, red algae, synchronization, temperature, trophic regimes,
• MeSH
• Cell Cycle physiology   MeSH
• Heterotrophic Processes physiology   MeSH
• Cells, Cultured MeSH
• Microalgae cytology   growth & development   MeSH
• Rhodophyta cytology   growth & development   MeSH
• Temperature MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Multiple fission is a cell cycle variation leading to the production of more than two daughter cells. Here, we used synchronized cultures of the chlorococcal green alga Parachlorella kessleri to study its growth and pattern of cell division under varying light intensities. The time courses of DNA replication, nuclear and cellular division, cell size, total RNA, protein content, dry matter and accumulation of starch were observed at incident light intensities of 110, 250 and 500 µmol photons m-2s-1. Furthermore, we studied the effect of deuterated water on Parachlorella kessleri growth and division, to mimic the effect of stress. We describe a novel multiple fission cell cycle pattern characterized by multiple rounds of DNA replication leading to cell polyploidization. Once completed, multiple nuclear divisions were performed with each of them, immediately followed by protoplast fission, terminated by the formation of daughter cells. The multiple fission cell cycle was represented by several consecutive doublings of growth parameters, each leading to the start of a reproductive sequence. The number of growth doublings increased with increasing light intensity and led to division into more daughter cells. This study establishes the baseline for cell cycle research at the molecular level as well as for potential biotechnological applications, particularly directed synthesis of (deuterated) starch and/or neutral lipids as carbon and energy reserves.

• Keywords
• Parachlorella kessleri, cell cycle pattern, deuterated lipid, deuterated starch, deuterium, energy reserves, growth processes, light intensity, reproduction events,
• MeSH
• Cell Culture Techniques * MeSH
• Cell Cycle * MeSH
• Chlorophyta growth & development   MeSH
• Light * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Extensive in vivo replacement of hydrogen by deuterium, a stable isotope of hydrogen, induces a distinct stress response, reduces cell growth and impairs cell division in various organisms. Microalgae, including Chlamydomonas reinhardtii, a well-established model organism in cell cycle studies, are no exception. Chlamydomonas reinhardtii, a green unicellular alga of the Chlorophyceae class, divides by multiple fission, grows autotrophically and can be synchronized by alternating light/dark regimes; this makes it a model of first choice to discriminate the effect of deuterium on growth and/or division. Here, we investigate the effects of high doses of deuterium on cell cycle progression in C. reinhardtii. Synchronous cultures of C. reinhardtii were cultivated in growth medium containing 70 or 90% D2O. We characterize specific deuterium-induced shifts in attainment of commitment points during growth and/or division of C. reinhardtii, contradicting the role of the "sizer" in regulating the cell cycle. Consequently, impaired cell cycle progression in deuterated cultures causes (over)accumulation of starch and lipids, suggesting a promising potential for microalgae to produce deuterated organic compounds.

• Keywords
• Chlamydomonas reinhardtii, cell cycle, cell division, commitment point, deuterium, heavy water, multiple fission, stress,
• MeSH
• Cell Division drug effects   MeSH
• Cell Cycle drug effects   MeSH
• Chlamydomonas reinhardtii growth & development   metabolism   MeSH
• Deuterium adverse effects   chemistry   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Deuterium MeSH

Temperature is one of the key factors affecting growth and division of algal cells. High temperature inhibits the cell cycle in Chlamydomonas reinhardtii. At 39 °C, nuclear and cellular divisions in synchronized cultures were blocked completely, while DNA replication was partly affected. In contrast, growth (cell volume, dry matter, total protein, and RNA) remained unaffected, and starch accumulated at very high levels. The cell cycle arrest could be removed by transfer to 30 °C, but a full recovery occurred only in cultures cultivated up to 14 h at 39 °C. Thereafter, individual cell cycle processes began to be affected in sequence; daughter cell release, cell division, and DNA replication. Cell cycle arrest was accompanied by high mitotic cyclindependent kinase activity that decreased after completion of nuclear and cellular division following transfer to 30 °C. Cell cycle arrest was, therefore, not caused by a lack of cyclin-dependent kinase activity but rather a blockage in downstream processes.

• Keywords
• Chlamydomonas reinhardtii, DNA replication, cell cycle arrest, cell size, cyclin-dependent kinase, starch accumulation, supraoptimal temperature, synchronized cultures,
• MeSH
• Algal Proteins metabolism   MeSH
• Cell Culture Techniques methods   MeSH
• Chlamydomonas reinhardtii cytology   physiology   MeSH
• Cyclin-Dependent Kinases metabolism   MeSH
• Down-Regulation MeSH
• Stress, Physiological MeSH
• Cell Cycle Checkpoints * MeSH
• Gene Expression Regulation, Plant MeSH
• Hot Temperature MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Algal Proteins MeSH
• Cyclin-Dependent Kinases MeSH

The worldwide growing demand for energy permanently increases the pressure on industrial and scientific community to introduce new alternative biofuels on the global energy market. Besides the leading role of biodiesel and biogas, bioethanol receives more and more attention as first- and second-generation biofuel in the sustainable energy industry. Lately, microalgae (green algae and cyanobacteria) biomass has also remarkable potential as a feedstock for the third-generation biofuel production due to their high lipid and carbohydrate content. The third-generation bioethanol production technology can be divided into three major processing ways: (i) fermentation of pre-treated microalgae biomass, (ii) dark fermentation of reserved carbohydrates and (iii) direct "photo-fermentation" from carbon dioxide to bioethanol using light energy. All three technologies provide possible solutions, but from a practical point of view, traditional fermentation technology from microalgae biomass receives currently the most attention. This study mainly focusses on the latest advances in traditional fermentation processes including the steps of enhanced carbohydrate accumulation, biomass pre-treatment, starch and glycogen downstream processing and various fermentation approaches.

• MeSH
• Biofuels analysis   MeSH
• Biotechnology MeSH
• Ethanol metabolism   MeSH
• Fermentation MeSH
• Microalgae metabolism   MeSH
• Polysaccharides metabolism   MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Biofuels MeSH
• Ethanol MeSH
• Polysaccharides MeSH

Most cells divide into two daughter cells; however, some green algae can have different division patterns in which a single mother cell can sometimes give rise to up to thousands of daughter cells. Although such cell cycle patterns can be very complex, they are governed by the same general concepts as the most common binary fission. Moreover, cell cycle progression appears to be connected with size, since cells need to ensure that their size after division will not drop below the limit required for survival. Although the exact mechanism that lets cells measure cell size remains largely unknown, there have been several prominent hypotheses that try to explain it.

• MeSH
• Cell Division * MeSH
• Cell Cycle * MeSH
• Chlorophyta cytology   growth & development   metabolism   MeSH
• Cell Size MeSH
• Publication type
• Journal Article MeSH
• Review MeSH