Abstract
The effluent from the biogas process was tested as a nutrient source during cultivation of the protein-rich and edible microalgae Spirulina (Arthrospira platensis) and compared with conventional Spirulina medium. Equal biomass production was observed until late exponential phase and no significant differences could be observed between the treatments in protein amount, amino acid composition, and total lipid concentration. The concentration of the pigment phycocyanin differed significantly between Spirulina medium and the effluent-based medium (63.3 ± 11.7 and 86.2 ± 1.9 mg g−1, respectively). Slightly higher concentrations of saturated fatty acids, mainly palmitic acid, were observed in the biomass produced in Spirulina medium than in that produced in the effluent-based medium. In the biomass produced in the effluent-based medium, the cadmium concentration was 0.07 ± 0.05 mg kg−1 of dry weight, whereas it was below the detection limit in the biomass produced in Spirulina medium. There is a need to identify new food and feed resources and a possible future scenario is to integrate Spirulina production into the biogas plant for protein production as it contains more than 60% of protein on dry weight basis. In that scenario, it is important to control heavy metal concentrations in the biogas slurry fed to Spirulina.
Highlights
The world’s population is increasing rapidly, and there is a need to identify new food and feed resources
Total concentration of protein, expressed as % of dry weight (DW), in the biomass harvested after 6 days of growth was 60.5 ± 6.2 and 63.3 ± 2.7 for Spirulina medium and effluent-based medium, respectively, and no significant differences were observed between the treatments
Total concentration of lipids in the biomass harvested after 6 days of growth was 34.8 ± 3.8 and 42.0 ± 4.2 lg mg-1 DW for Spirulina medium and effluent-based medium, respectively, and no significant differences were observed between the treatments
Summary
The world’s population is increasing rapidly, and there is a need to identify new food and feed resources. One possibility to meet the need for high-quality protein is through increased production of the microorganism known as Spirulina. Spirulina is a multicellular edible cyanobacterium, capable of photosynthesis, that is traditionally used as a food source in Mexico and parts of Africa. Dried Spirulina biomass contains approximately 60% protein, which is high compared with traditional protein crops, such as soybean. Spirulina contains all essential amino acids and high-quality lipids, with a substantial amount of polyunsaturated fatty acids [2]. It should be pointed out that in contrast to traditional crops, such as soybean, Spirulina does not require arable land for its production. Suitable for food production in the vicinity of nutrient-rich wastewater streams, regardless of the availability of soil, e.g., in urban or peri-urban areas
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