Long-Term Cultivation of a Native Arthrospira platensis (Spirulina) Strain in Pozo Izquierdo (Gran Canaria, Spain): Technical Evidence for a Viable Production of Food-Grade Biomass

Abstract

Microalgae cultivation is a promising alternative to traditional agriculture in arid—semi-arid areas. The aim of this study is to assess the viability of long-term cultivation of native Arthrospira platensis in Gran Canaria. Maximum culture productivity (0.08 g/L/day) and optimal concentration range (0.6–0.9 g/L) were firstly determined in 8000 L raceway under a greenhouse. Afterwards, a stable productivity of 0.06 g/L/day (6.0 g/m2/day) was obtained by reusing the culture medium during 26 days of cultivation, with consistent biomass biochemical composition. Outdoor temperature and daily solar irradiation ranged between 17.9–30.7 °C and 79.2–274.8 W/m2, while culture pH and salinity were in the range 9.42–10.77 and 11.2–14.9 g/L, respectively. Protein (>60%), potassium (1.8 g/100 g) and C-phycocyanin (7.2%) content is in the high-range of commercial Spirulina, which makes BEA 1257B promising for food and extraction of natural pigments/antioxidants. The dried biomass complies with international standards for human consumption, because of low heavy metal content and no pathogens presence. Product quality can be improved by reducing ash (≃12%) and sodium (1.5%) content through biomass washing optimization and/or further dewatering step. Other microorganisms can be prevented by high alkaline conditions and mild chemical treatments. These results pave the way for a sustainable microalgae-based blue bioeconomy in the Canary Islands.

Characterization of Microalgae Biomass-Based Composites Obtained through Rotational Molding

“…Optical microscopy was used for morphological identification, and 16S gene sequencing (GenBank MT426015) confirmed the identity of the species. At the Canarian Institute of Technology (ITC), the culture was scaled up from a culture chamber (8 L inoculum) to outdoor raceway reactors of increasing volumes (from 250 L to 1600 L) up to a 80 m 2 raceway reactor; here, A. platensis was grown semi-continuously in 100% seawater with a culture medium modified by Guidi et al [21].…”

“…The algal slurry obtained after harvesting was either washed (5 L freshwater kg −1 biomass) and manually pressed through a 30 µm nylon net before freezing at −20 • C, or frozen directly without further processing. Washing and pressing allowed us to obtain a reduction in biomass salt content (as suggested by Guidi et al [21]). Afterwards, all biomasses were dehydrated by spraydrying (Model L-12, Ohkawara Kakohki Co., Ltd., Yokohama, Japan), obtaining a dried washed/pressed biomass (thereinafter Sp) and a dried unwashed/non-pressed biomass (thereinafter Sp.N.W).…”

“…Mass cultures of microalgae are regarded as a promising alternative to traditional terrestrial crops for the production of food, feed and biofuels, among other products. Outdoor microalgal cultures present several advantages, such as fast growth with high yields, when performed in non-arable land and with the use of low-quality (and low cost) water, such as seawater, wastewater or brackish water; furthermore, exhaust gases with CO 2 can be used as a carbon source during cultivation [21]. Moreover, microalgae can be used in waste water treatment, as they are able to absorb excess nutrients from waste water [22].…”