The Red MicroalgaGaldieriaas a Promising Organism for Applications in Biotechnology

Abstract

The genus Galdieria refers to red algae and includes microscopic inhabitants of highly acidic (pH 1-2), often volcanic habitats. They are thermophilic or thermo-tolerant organisms, some of them surviving temperatures up to 56°C. As other extremophilic microorganisms, they exhibit unique features derived from their modified metabolisms. In this chapter, we will review the special abilities of Galdieria species such as metabolic flexibility to grow photoautotrophically, heterotrophically or mixotrophically, ability to utilize a whole range of unusual carbon sources, capability of surviving extreme environments or their extremely high resistance to metals. We will discuss the potential of Galdieria for applications in biotechnology, for example, phycocyanin production, nutrient removal from urban wastewaters, bio-mining, treatment of acidic mine drainage, selective metal precipitation, bioremediation of acidic metal-contaminated areas or recovery of critical and scarce metals from secondary sources.

Removal of sugars in wastewater from food production through heterotrophic growth of Galdieria sulphuraria

“…Biomass concentrations of 80–120 g·L −1 cell dry weight could be obtained with glucose in fed‐batch and continuous‐flow cultivation, which demonstrates that this algae is well suited for high cell density cultivations [30–32]. This unique metabolism combined with selective growth conditions of pH 1–4 and temperatures up to 56°C makes G. sulphuraria a promising organism for the utilization of waste streams [33]. G. sulphuraria was already successfully grown on hydrolysates of restaurant and bakery waste [34].…”

Extremophile Microalgae: the potential for biotechnological application

“…, Hirooka and Miyagishima , Čížková et al. ). An extreme form of metal tolerance is found in those organisms that can grow in the presence of radionuclides and which are therefore extremely resistant to ionizing radiation (Varshney et al.…”

Cultivation of the Acidophilic Microalgae Galdieria phlegrea with Wastewater: Process Yields

“…Several factors affect the selection of the strain to be used. For example, to maximize the extraction of compounds of high biotechnological value such as phycocyanin or glycogen, the latter being a potential food supplement in the nutraceutical sector [ 29 ], preference should be given to a strain that exhibits a higher yield of such compounds, while being able to thrive in urban wastewater. Nevertheless, particular attention should be paid to the selection of an algal strain which is able to properly reduce not only the pollutant load of the sewage, but also the community of pathogens naturally living in the wastewater.…”

“…It has a significant flexibility of adaptation to pH up to 5.5, despite its natural conditions characterized by a pH below 2 [ 35 ]. Galdieria has high potential in biotechnological applications and it is a reliable means for applications in bio-based remediation processes because of its natural ability to cope with and neutralize biohazardous heavy metals [ 37 ] typically present in volcanic areas and acid mines, thanks to the presence of a wide variety of carriers [ 29 ]. Moreover, being able to tolerate temperatures up to 56 °C [ 29 ], these microalgae can be cultivated in closed photobioreactors exposed to full sunlight and high diurnal temperatures without energy-consuming cooling technologies [ 24 ], thus achieving a reduction in energy costs of the system.…”

“…Galdieria has high potential in biotechnological applications and it is a reliable means for applications in bio-based remediation processes because of its natural ability to cope with and neutralize biohazardous heavy metals [ 37 ] typically present in volcanic areas and acid mines, thanks to the presence of a wide variety of carriers [ 29 ]. Moreover, being able to tolerate temperatures up to 56 °C [ 29 ], these microalgae can be cultivated in closed photobioreactors exposed to full sunlight and high diurnal temperatures without energy-consuming cooling technologies [ 24 ], thus achieving a reduction in energy costs of the system. Furthermore, these organisms draw a lot of interest because they exhibit high phycocyanin levels, ≈1–2 orders more than other species, while being able to accumulate under appropriate conditions up to 50% of glycogen, the latter having a lower molecular weight and a more branched chain compared to the one produced by other organisms [ 29 ].…”