Techno-economic modelling of high-value metabolites and secondary products from microalgae cultivated in closed photobioreactors with supplementary lighting

Chemical Characterization, Lipid Profile, and Volatile Compounds in Chlorella sp. and Spirulina platensis: A Promising Feedstock for Various Applications

Microalgae are among the most promising feedstocks for a wide range of applications due to their ease of cultivation, rapid growth rate, and ability to accumulate significant amounts of lipids and other valuable compounds. In the current study, two microalgae species, Chlorella sp. and Spirulina platensis, were studied regarding chemical composition, lipid extraction by ultrasound-assisted solvent extraction, and volatile compounds analysis. The optimization of the lipid extraction process was investigated with respect to the influence of different process parameters. The highest lipid content was found in Chlorella sp., which was more than twice as high compared to Spirulina platensis. Both microalgae contain saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs). Spirulina platensis contains high palmitic acid (42.9%) and linolenic acid (22.5%), and is low in MUFA content (8.5%), whereas Chlorella sp. contains high oleic (21.9%), linoleic (25.3%), and α-Linolenic acid (10.2%). Based on the fatty acids profile, nutritional lipid indices were calculated. Regarding the volatile content, Spirulina platensis contains amines, aldehydes, alcohols, ketones, and hydrocarbons, whereas Chlorella sp. contains hydrocarbons, heterocycle, aldehydes, thiocyanates, and esters which give the odor profile.

Microalgae production in human urine: Fundamentals, opportunities, and perspectives

The biological treatment of source-separated human urine to produce biofuel, nutraceutical, and high-value chemicals is getting increasing attention. Especially, photoautotrophic microalgae can use human urine as media to achieve environmentally and economically viable large-scale cultivation. This review presents a comprehensive overview of the up-to-date advancements in microalgae cultivation employing urine in photobioreactors (PBRs). The standard matrices describing algal growth and nutrient removal/recovery have been summarized to provide a platform for fair comparison among different studies. Specific consideration has been given to the critical operating factors to understand how the PBRs should be maintained to achieve high efficiencies. Finally, we discuss the perspectives that emphasize the impacts of co-existing bacteria, contamination by human metabolites, and genetic engineering on the practical microalgal biomass production in urine.

Microalgae-Based Biorefineries: Challenges and Future Trends to Produce Carbohydrate Enriched Biomass, High-Added Value Products and Bioactive Compounds

Simple Summary

Microalgae-based biorefineries allow the simultaneous production of microalgae biomass enriched in a particular macromolecule and high-added and low-value products if a proper selection of the microalgae species and the cultivation conditions are adequate for the purpose. This review discusses the challenges and future trends related to microalgae-based biorefineries stressing the multi-product approach and the use of raw wastewater or pretreated wastewater to improve the cost-benefit ratio of biomass and products. Emphasis is given to the production of biomass enriched in carbohydrates. Microalgae-bioactive compounds as potential therapeutical and health promoters are also discussed. Future and novel trends following the circular economy strategy are also discussed.

Abstract

Microalgae have demonstrated a large potential in biotechnology as a source of various macromolecules (proteins, carbohydrates, and lipids) and high-added value products (pigments, poly-unsaturated fatty acids, peptides, exo-polysaccharides, etc.). The production of biomass at a large scale becomes more economically feasible when it is part of a biorefinery designed within the circular economy concept. Thus, the aim of this critical review is to highlight and discuss challenges and future trends related to the multi-product microalgae-based biorefineries, including both phototrophic and mixotrophic cultures treating wastewater and the recovery of biomass as a source of valuable macromolecules and high-added and low-value products (biofertilizers and biostimulants). The therapeutic properties of some microalgae-bioactive compounds are also discussed. Novel trends such as the screening of species for antimicrobial compounds, the production of bioplastics using wastewater, the circular economy strategy, and the need for more Life Cycle Assessment studies (LCA) are suggested as some of the future research lines.