National Repository of Grey Literature 2 records found  Search took 0.00 seconds. 
Life cycle of Haematococcus pluvialis (Chlorophyceae) species complex
Vávrová, Karolína ; Němcová, Yvonne (advisor) ; Nedbalová, Linda (referee)
Freshwater green algae within species complex Haematococcus pluvialis are best natural producers of secondary carotenoid astaxanthin famous for its strong antioxidant activity. Despite worldwide distribution, great biotechnological potential and extensive literature dealing with different approaches to the cultivation of these organisms, there still remains surprising gaps in knowledge of their complex life cycle and behaviour. First uncertainty concerns asexual cell division of zoospores, hypothetically limited to five cell doublings (Lee & Ding 1994). No such genetic limitation was observed in this thesis, number of cell divisions is thus influenced mainly by cultivation conditions. There is still considerable uncertainty regarding to the asexual reproduction, as well. Ambiguity might be caused by scarce observation of the whole process of gametogenesis and conjugation of gametes. Published studies differed in some particular points. Unfortunately, we did not succeed in induction of gametogenesis despite broad scale of tested cultivation conditions applied to two different species within the H. pluvialis complex, namely H. pluvialis and H. rubicundus. This failure might be caused by heterothalism of the studied strains. Haematococcus pluvialis inhabits mainly ephemeral pools. Its ability to...
Cell cycle of astaxanthin producing green alga Haematococcus pluvialis, culture media and cultivation conditions
Vávrová, Karolína ; Němcová, Yvonne (advisor) ; Pichrtová, Martina (referee)
Haematococcus pluvialis is unicellular green alga (Chlorophyceae, Chlamydomonadales), which can be found in ephemeral rock pools and birdbaths. It is the best natural producer of strong antioxidant astaxanthin, red secondary carotenoid used as coloring agent in aquaculture and poultry breeding. Astaxanthin also has various positive effects on human health. Haematococcus pluvialis has quite complex life cycle consisting of four life stages, biflagellated zoospores, non- motile round palmella stage, thick-walled akinetes (aplanospores, cysts) with high content of astaxanthin and small biflagellated gametes. Akinetes, which enable H. pluvialis to survive desiccation in its natural habitat, are formed in response to stress conditions such as high irradiance and temperature and nutrient depletion. Cells undergo dramatic ultrastructural changes during aplanospore formation. Chloroplast volume is decreased, synthesis of high amount of astaxanthin and fatty acids results in presence of lipid droplets that spread from the center to the periphery of the cell and thick cell wall containing algaenans is formed. Cultivation of H. pluvialis is often performed in two subsequent stages, green stage focused on biomass production and red stage focused on astaxanthin accumulation under stress conditions. There are...

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