Influence of silicate on enrichment of highly productive microalgae from a mixed culture

Abstract

Microalgae have the potential to supply a biobased society with essential feedstocks like sugar and lipids. Besides being productive, strains used for this purpose should grow fast, be resistant to predators, and have good harvestability properties. Diatoms, a class of siliceous algae, have these and other preferred characteristics. In this paper, we describe the enrichment of microalgae in sequencing batch reactors with and without supply of silicate. Both reactors were operated with a light–dark cycle. To maximize storage compound production, carbon fixation and nitrogen uptake were uncoupled by limiting the availability of nitrate to the dark phase. After ten cycles, a stable culture was established in both reactors. The diatom Nitzschia sp. dominated the silicate-rich reactor, and the green algae Chlamydomonas sp. dominated the silicate-depleted reactor. Over the remaining 27 cycles of the experiment, the microalgal community structure did not change, indicating a highly stable system. Although the dominant microalga was highly dependent on the presence of silicate, the performance of both microalgal enrichments was similar. Polymers of glucose were stored during the nitrogen-limited light period. On organic matter dry weight basis, the sugar content of the biomass increased during the light period from 17 ± 4 to 53 ± 4 % for the silicate-limited culture, and from 14 ± 4 to 43 ± 4 % (w w−1) for the silicate excess culture. These results show that storage compound production can be achieved under various conditions, as long as a selective environment is maintained.

Potential of diatom consortium developed by nutrient enrichment for biodiesel production and simultaneous nutrient removal from waste water

“…Although the biomass productivity found in this study was low compared to that of previous studies ( Table 3 ), these values were obtained by using a mixture of diatom strains rather than single-species cultures grown in a laboratory; thus, additional optimization is required to reach maximum productivity. In a similar study by Mooij et al (2015) on silica replete and deplete batch reactors with a mixed algal consortium, Si excess resulted in cultures with diatom Nitzschia dominance; in Si-depleted medium, green algae Chlamydomonas dominated the culture ( Mooij et al, 2015 ) supporting that silica enrichment resulted in an algal consortium dominated by diatoms. In freshwater, silica is less soluble than amorphous silica.…”

Influence of Carbohydrate Additives on the Growth Rate of Microalgae Biomass with an Increased Carbohydrate Content

“…As a storage compound, carbohydrates provide the energy needed for the metabolism of the microalgae and allow them to survive temporarily in the dark when needed [ 15 , 16 ]. Microalgae components (such as proteins, lipids, and carbohydrates) allow them to adapt to changing environmental conditions for their growth [ 17 , 18 ]. Carbohydrates are a broad category that includes sugars (monosaccharides) and their polymers (disaccharides, oligosaccharides, and polysaccharides) [ 19 , 20 ].…”

Effect of the deficiency of nitrate and silicate on the growth and composition of the benthic diatom Navicula incerta

“…For years, microalgae have been used for feeding animals and humans (García-González et al, 2005). They are highly efficient in producing a wide variety of chemical components, such as fatty acids, pigments and other biologically active compounds of interest (Rema & Gouveia, 2005;Yaşar & Şevket, 2006;Mooij et al, 2016). The genus Navicula is a __________________ Corresponding editor: José Luis Iriarte benthic diatom that presents great potential for the production of these compounds (Leal et al, 2013;Fimbres-Olivarría et al, 2015).…”

“…Also, they are already used for their high production of fatty acids for aquaculture and human consumption. Generally, microalgae have been predicted to be an essential supply feedstock for food, fuels and chemicals in a biobased economy (Wijffels & Barbosa, 2010;Mooij et al, 2016). For these reasons, it is important to seek the best growth conditions to produce these compounds.…”