Chlorella Pyrenoidosa Case Study

Chlorella pyrenoidosa is a widely available microalga with several commercial applications for food and nutritional purposes. It has also revealed great potential as future industrial bioenergy producer due to its robustness, high growth rate, and high carbohydrate and lipid contents, and can be cultured under autotrophic, heterotrophic and mixotrophic conditions. However, in presence of organic carbon sources, it produces higher biomass with better carbohydrate contents than its autotrophic cultures (Miao and Wu, 2004; 2006; Liang et al. 2009). Mixotrophic growth occurs when CO2 and organic carbon are assimilated in cells simultaneously. There are a number of algae that are facultative heterotrophic and prefer an organic carbon substrate,
Certain species of algae have the ability to produce high levels of carbohydrates instead of lipids as reserve polymers. These species are ideal candidates for the production of bioethanol as carbohydrates from algae can be extracted to produce fermentable sugars. In addition, microalgae-based carbohydrates are mainly in the form of starch and cellulose (with the absence of lignin), are thus much easier to convert to monosaccharides when compared with lignocellulosic materials (Harun et al., 2010; Ho et al., 2012; John et al., 2011). Many researchers have reported that the genus of Chlorella possess has a high carbohydrate content, especially the species of Chlorella vulgaris, with carbohydrates being 37-55% of its dry weight (Brennan and Owende, 2010; Dragone et al., 2011; Illman et al., 2000). The carbohydrates in green algae mainly come from starch in chloroplasts and cellulose/polysaccharides on cell walls (Richmond, 2004). The growth of microalgae and the composition of microalgae biomass are known to be greatly dependent on the light supply (type of light source and light intensity) (Ogbonna and Tanaka, 2000) medium composition (especially Carbon and nitrogen sources) (Li et al. 2008; Liu et al. 2008; Liang et
Notice that those biochemical compositions were analyzed simultaneously by a FT-IR spectrometer (Pistorius et al., 2009), because the acyl chains of lipids, the amide groups of peptides, and C–OH, C–O–C groups of carbohydrates occurred at 2800–3000 cm¯1, 1500–1700 cm¯1and 1000–1200 cm¯1, respectively. In this study C. pyrenoidosa was used to study as model strain for the investigation of microalgae cultivation strategy. As medium composition (organic carbon sources and nitrogen sources) is known to play a pivotal role in the efficiency of microalgal growth (reference), the effect of pH, the effect of different types of C, N sources and varying concentration of most appropriate C, N source on the growth and biomass yield of heterotrophic and mixotrophic regimen C. pyrenoidosa were investigated. In addition to optimizing the heterotrophic and mixotrophic cultivation condition, the growth potential of autotrophic regimen selected algal strain in various concentration of sodium bicarbonate, the effect of photoperiods and the effect of pH was investigated. The influence of cultivation conditions on the cell growth, carbohydrate accumulation and other biochemical composition of cells were further discussed and illustrated by a schematic which was also useful for other microalgal