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Production of Biofuels from Algal Biomass
Published in M. Jerold, V. Sivasubramanian, Biochemical and Environmental Bioprocessing, 2019
Murali Mohan Seepana, M. Jerold, K. S. Rajmohan
Microalgae can be classified as heterotrophic, autotrophic, and mixotrophic depending on their way of growth (Liang et al., 2009). Heterotrophic algae are grown in the absence of sunlight (dark) with a continuous supply of organic carbon source, whereas, in autotrophic cultivation, daylight from sun acts as the energy source while CO2 is utilized as a carbon source in addition to essential minerals and vitamins. A third type of algae, which grows in the presence of light and requires an organic carbon source, is known as mixotrophic algae, and the growth can be heterotrophic or phototrophic according to the culture conditions. Photobioreactors (PBRs) can be employed for three types of cultivation conditions, and the cost involved and challenges are summarized in Table 7.2 (Chen et al., 2011). Among the three, mixotrophic cultivation is known to result in enhanced biomass yield as it offers the combined benefits of heterotrophic and autotrophic cultivation methods. Currently, two major microalgal cultivation techniques are used, i.e. open pond and closed-loop systems, which are described as follows.
Biofuel production from algal biomass
Published in Ozcan Konur, Bioenergy and Biofuels, 2017
Jonah Teo Teck Chye, Lau Yien Jun, Lau Sie Yon, Sharadwata Pan, Michael K. Danquah
In addition to nutrients such as phosphorus, nitrogen, potassium, zinc, and calcium, microalgal cultivation requires water, carbon dioxide, and sunlight to produce biomass through photosynthesis, by transforming solar energy into organic chemical energy stored in the microalgal cells. Three major types of microalgae cultivation techniques have been established based on their growth conditions: photoautotropic, heterotrophic, and mixotrophic cultures. Photoautotrophic cultivation utilizes light as the sole energy source that is converted to chemical energy through photosynthetic reactions. Conversely, heterotrophic production requires organic carbon materials as carbon and energy source to simulate growth. In mixotrophic cultivation, the organisms are able to thrive either autotrophically or heterotrophically, depending on the concentration of organic compounds and available light intensity. Among the aforementioned methods, photoautotrophic production is most widely used because it is economically feasible and suitable for large-scale algal biomass production. The choice of microalgal cultivation system from the most commonly available ones, whether open, closed, or hybrid, is made based on the products and the strains to be cultivated (Gambelli et al., 2017; Narala et al., 2016).
Mechanisms for Carbon Assimilation and Utilization in Microalgae and Their Metabolites for Value-Added Products
Published in Ashok Kumar, Swati Sharma, 2 Utilization, 2020
Varsha S.S. Vuppaladadiyam, Zenab T. Baig, Abdul F. Soomro, Arun K. Vuppaladadiyam
Mixotrophic metabolism allows the flexibility to simultaneously use both photoautotrophic and heterotrophic metabolic strategies (e.g. light and/or organic chemical energy sources) along with the possibility to switch between them. As shown in Figure 12.1, in the mixotrophic metabolism, the acetyl-CoA pool is sustained via the combined use of extracellular organic carbon and CO2 (Mohan et al. 2015). Organic carbon and inorganic carbon are assimilated through aerobic respiration and photosynthesis, respectively (Hu et al. 2012). This arrangement to switch between strategies enables a higher biomass productivity (Wang, Yang, and Wang 2014).
Astaxanthin from Haematococcus pluvialis: processes, applications, and market
Published in Preparative Biochemistry & Biotechnology, 2022
Géssica Cavalcanti Pereira Mota, Laenne Barbara Silva de Moraes, Carlos Yure B. Oliveira, Deyvid Willame S. Oliveira, Jéssika Lima de Abreu, Danielli Matias M. Dantas, Alfredo Olivera Gálvez
Haematococcus pluvialis, in response to environmental changes, alters its metabolic routes, adapting itself to different growth conditions. By that, this microalga presents the ability to grow photoautotrophically, heterotrophically, or even mixotrophically.[57,61] Under the photoautotrophic metabolism, the cells use inorganic carbon and light as an energy source, using oxygenic photosynthesis as an energy conversion mechanism. Still, under the heterotrophic metabolism, organic carbon is used as a source of energy and carbon, and cultures are carried out in the dark, as photosynthesis does not occur for light energy conversion. On the other hand, under the mixotrophic metabolism, the cells use light, inorganic and organic carbon simultaneously, promoting their growth by both oxygenic photosynthesis and heterotrophic respiration.[62]
Current research and perspectives on microalgae-derived biodiesel
Published in Biofuels, 2020
Kartik Singh, Deeksha Kaloni, Sakshi Gaur, Shipra Kushwaha, Garima Mathur
A carbon source is essential in algal growth and reproduction. Photoautotrophic cultivation means utilizing light as the sole source of energy that is further converted to chemical energy through photosynthetic reactions [50]. Other microalgal strains may use organic carbon (heterotrophic cultivation); however, this mode of production is only useful to produce high-value compounds. The mixotrophic nutrition mode is the combination of autotrophic and heterotrophic mechanisms.