Harvest of the Oleaginous Microalgae Scenedesmus obtusiusculus by Flocculation From Culture Based on Natural Water Sources

Abstract

Harvest and dewatering poses a significant economical burden for industrial algae biomass production. To mitigate these effects, energy efficient techniques for these process steps have to be developed. Flocculation of the microalgae Scenedesmus obtusiusculus in salt based medium was induced by pH-shift and alternatively by addition of two biological flocculants, chitosan, and the commercial tannin CFL-PT. This is the first time that CFL-PT is used as an algae flocculant particularly focusing on harvesting of halophilic strains. The method was characterized and subsequently optimized. In comparison to biological flocculants, induction by pH shift is far cheaper, but due to buffering effects of the brackish cultivation medium infeasible amounts of base are required to raise the pH-value. tannin appears to be superior compared to chitosan not only in the absence of algae organic matter (AOM), but tannin-based harvest is also more robust regarding culture pH in presence of AOM. A higher flocculant-demand for modified tannin compared to chitosan is offset by the lower price. Given the employed strain and cultivation conditions, cultivation time had no pronounced effect on flocculation efficiencies (FE) while algae zeta-potential and bacterial communities also remained stable.

Cultivation of Oily Microalgae for the Production of Third-Generation Biofuels

“…The tannin appears to be favorable for culturing the microalgae when compared to chitosan in the absence as well as in the presence of algae organic matter (AOM). The cultivation time did noticeably affect the flocculation efficiencies of tannin and other parameters like algae zeta potential and bacterial communities presence remained stable when tannin was used as a flocculant [22].…”

“…Bracharz et al [22] have reported, for the first time, the use of chitosan and tannin (CFL-PT) as an algae flocculant that focuses on harvesting halophilic strains. The cost of the harvesting and dewatering process is significantly high for industrial-scale production.…”

“…Various studies on the growth media and cultivation systems used for oleaginous microalgae are shown in Table 2. The advancement in science and engineering should be blended together to produce novel systems that can increase the yield and productivity of microalgae to produce required biomolecules in a more feasible way [22]. Table 3.…”

A review on microalgae cultivation and harvesting, and their biomass extraction processing using ionic liquids

“…Flocculating agents can be grouped into two major types, namely chemical flocculants and bio-flocculants. Low cost and highly available chemical flocculants such as iron and aluminum salts have been used widely in industry [59]. The study carried out by Chatsungnoen and Chistt [60] has demonstrated that the metal salts such as aluminum sulfate and iron chloride are able to remove 95% of the microalgae biomass at a standard condition.…”

Isolation of Industrial Important Bioactive Compounds From Microalgae: A Review

“…(a) Biomass aggregation: In the flocculation technique, microalgae cells are aggregated together to form a larger particle known as floc, with the addition of flocculants such as multivalent cations and cationic polymers to the media which help neutralised the cells surface charge [12]. There are two [13]. However, toxic effects can occur when using chemical, causing contamination to the biomass.…”