8. Concluding remarks

biofuel productivity by sequestration of the CO2 produced in the power plant [35]. Productivity of biodiesel from oily plant crops, in terms of produced oil by surface production, varies from 27.57 to 972 L per ha, whereas that from microalgae culti-

Biofuels derived from algal biomass depend on algal species: for biodiesel,

Palmaria, Porphyra, Ascophyllum, Ulva lactuca,Tetraselmis sp., and Chlorococum sp.; and for biogas C. reinhardtii, Chlorella kessleri, and Spirogyra neglecta [23, 41–44]. To produce biodiesel from microalgae, it is very important to select strains with oil content over 50% to improve biodiesel yield. With respect to oil content, microalgae

Soluble proteins have been used as nutritional supplements and personal care products or insoluble proteins for animal feeds [36]. Protein production has been reported in S. platensis using beet vinasse-supplemented culture media, in tubular photobioreactor biomass, which reached to 6.5 g L<sup>1</sup> and 168 mg L<sup>1</sup> d<sup>1</sup> of protein productivity. Continuous cultivation was also suitable for protein production from

Incorporation of carbon from an organic carbon source, the type of carbon source, the amount supplemented to the culture, and the specie of microalgae are important for lipid accumulation in the cells of microalgae. The content of protein mostly increases by the addition of an organic carbon source, but lipid content decreases, although productivity of biomass, protein, and lipids increases substan-

Figure 2 represents the secondary metabolite production along with biomass that should be included in balance equations. The main components are carbon, hydrogen, oxygen, and nitrogen; in other words, a secondary metabolite can be a fraction of the total biomass, and it can be defined as ΘΔX, where is the fraction corresponding to the secondary metabolite produced, for chlorophyll accumulation,

and it depends on the availability of carbon and nitrogen sources [40].

Drawing describing the production of secondary metabolites under mixotrophy. P, metabolite from autotrophy and heterotrophy; A, biomass from autotrophy; H, biomass from heterotrophy. Modified from

Cladophora fracta, C. protothecoides, and B. braunii; for biohydrogen, C. protothecoides, S. platensis, and Chlamydomonas reinhardtii; for bioethanol

can be divided into low, medium, and high oil content strains [45].

S. platensis using a medium supplemented with beet vinasse [46].

tially in the presence of organic carbon source [38].

vation is 7688–23,067 L per ha [23].

Microalgae - From Physiology to Application

7.5 Proteins

Figure 2.

Ref. [5].

202

In the past, microalgae cultures were used as components of aquaculture feeds and human food supplements. Recently, new alternatives have been opened for the production of fine chemicals and biofuels. However, production costs have been a concern; several efforts have been made to reduce processing costs to construct a profitable process. In this context, Allen et al. propose an integration of biology, ecology, and engineering topics for a sustainable biofuel and bioproduct production from microalgae [48].

The potential markets of value-added products from microalgae are nutraceuticals for human applications and nutraceutical with applications for animal and fish feed, bulk chemicals, and biofuels, with commercial costs of 100 €/kg biomass, 5–<sup>20</sup> €/kg biomass, <sup>&</sup>lt;<sup>5</sup> €/kg biomass, and <sup>&</sup>lt;0.4 €/kg biomass, with a volume market of 60 million, 3–4 billion, <sup>&</sup>gt;50 billion, and <sup>&</sup>gt;1 trillion €, respectively [49].

High value-added products such as antiviral, anticancer, and antioxidants are target products to be obtained from microalgae, since it is an alternative process that can be continuously cultivated of axenic cultures in a closed photobioreactor adapted with a special light source of irradiation, such as fiber-optic or halogen lamps. In this case, biomass increases as long as microalgae receive light and the broth hydrodynamic allows enough movement to reach the illuminated surface (see Table 1), in continuous cultivation. Once the light limitation occurred and due to the effect of washing out, biomass starts to decrease to a new dilution rate. When an organic carbon source has a positive effect on the growth, continuous cultivation can be used as well, to produce an increment in biomass density (Table 1) and secondary metabolite formation as well, producing an increment of biomass and in the metabolites. Productivity also has a substantial increment at same light intensity and same dilution rate (D, h<sup>1</sup> ). Productivity and biomass concentration have been obtained in semicontinuous cultivation with a biomass of 5.31 g L<sup>1</sup> and productivity of 1.32 g L<sup>1</sup> d<sup>1</sup> [50]. Therefore, semicontinuous cultivation seems to be a good strategy as well.

Secondary metabolite production can be effectively improved, by three advantages,(i) using a continuous process (up- and downstream processes),


#### Table 1.

Biomass concentration and productivity in continuous culture, in autotrophic and mixotrophic conditions (D = 0.03 h<sup>1</sup> ).

#### Figure 3.

Schematic representation of a series of photobioreactors to operate in continuous cultivation to produce fine chemicals.

(ii) implementing mixotrophic cultivation, and (iii) recycling broth medium at least three times (Figure 3).

Author details

Facundo J. Márquez-Rocha<sup>1</sup>

Microalgae Cultivation for Secondary Metabolite Production

DOI: http://dx.doi.org/10.5772/intechopen.88531

Jenny F. López-Hernández<sup>4</sup>

and Abelardo I. Flores-Vela<sup>2</sup>

Cunduacan, Tabasco, Mexico

Ciudad de México, Mexico

Tabasco, Mexico

205

University of Tabasco, Tabasco, Mexico

provided the original work is properly cited.

\*, Diana Palma-Ramírez<sup>2</sup>

1 Regional Center for Cleaner Production, National Polytechnic Institute,

2 Mexican Center for Cleaner Production, National Polytechnic Institute,

3 Academic Division of Agriculture and Livestock Science, Juarez Autonomous

4 Academic Division of Biological Sciences, Juarez Autonomous University of

5 Institute of Industries, University of the Sea, Puerto Angel, Oaxaca, Mexico

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: fjmrocha97@gmail.com

, Ivonne S. Santiago-Morales<sup>5</sup>

, Pedro García-Alamilla<sup>3</sup>

,
