Abstract
A major disadvantage of microalgal cultivation is limited biomass yields due to the autotrophic lifestyle of most microalgal species. Heterotrophic growth on a suitable carbon source and oxygen can overcome such limitations. The red microalga Galdieria sulphuraria strain 074G grows heterotrophically on glucose and a number of other carbon sources while constitutively producing photopigments, including the blue-colored phycocyanin, a natural food colorant. Galdieria sulphuraria strain 074G grew well on maltodextrins as well as on granular starch in combination with the enzyme cocktail Stargen002. The maltodextrin cultures produced 2 mg phycocyanin per gram substrate, being slightly more than on glucose. The phycocyanin extracted from maltodextrin-grown cultures was thermostable up to 55 °C. Maltodextrins can be a cheap alternative to glucose syrups for the production of phycocyanin as natural food colorant.
Highlights
Microalgae attract much attentions as they produce various organic compounds such as lipids, starch, and pigments that can be used as a renewable resources in the production of biodiesel, food supplements, or coloring agents (Mulders et al 2014; Raheem et al 2015; Rasala and Mayfield 2015; Wang et al 2015)
As in the previous study by Schmidt et al (2005), G. sulphuraria was able to grow in various simple sugars as the carbon source, such as glucose, fructose, sucrose, and maltose in order to evaluate its pigmentation
In the media containing 10 g L−1 of Paselli SA2, it was observed that the substrate was not totally consumed, in opposition to the medium with 10 g L−1 D-glucose, where glucose gradually decreased over time and was almost completely depleted before the end of cultivation (14 days of growth) (Fig. 1)
Summary
Microalgae attract much attentions as they produce various organic compounds such as lipids, starch, and pigments that can be used as a renewable resources in the production of biodiesel, food supplements, or coloring agents (Mulders et al 2014; Raheem et al 2015; Rasala and Mayfield 2015; Wang et al 2015). A major disadvantage of microalgae is that most species grow strictly autotrophic using (sun)light as energy source and carbon dioxide to form new organic matter. Heterotrophic growth does not suffer from such disadvantages and can give substantially higher growth rates and biomass yields, especially when specific cultivation strategies like fedbatch are applied (Morales-Sanchez et al 2013). A limited number of microalgae are able to grow heterotrophically depending on the strain and culture conditions (Chen and Chen 2006), examples being Tetraselmis chuii (Lu et al 2017), Chlamydomonas reindhardtii (Zhang et al 2019), Nitzschia laevis (Wen and Chen 2002), and Neochloris oleoabundans (Morales-Sanchez et al 2013)
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