Abstract
Euglena gracilis (E. gracilis) accumulates paramylon, an immune-functional beta-glucan that can be used as a functional food. Paramylon production is strongly affected by the organic carbon source and the initial pH conditions. Food processing byproducts have attracted attention for microalgal cultivation because of their low cost and abundance of nutrients, including carbon and nitrogen. We investigated the optimal carbon source and its concentration for efficient paramylon production. A spent tomato byproduct (STB) generated from a tomato processing plant was applied for biomass and paramylon production from E. gracilis with respect to the initial pH condition. The highest paramylon concentration (1.2 g L−1) and content (58.2%) were observed with 15 g L−1 glucose. The biomass production increased when STB was used as compared with that when a synthetic medium was used (1.6-fold higher at pH 3 and 2-fold higher at pH 8). The optimal initial pH was determined according to the maximum production of biomass and paramylon. Upcycling the food processing byproduct, STB, can contribute not only to cost reduction of the biorefinery process using E. gracilis but also to environmental remediation by removing organic carbon and nitrogen from the byproducts.
Highlights
The biomass and paramylon concentrations observed using lactate as the carbon source were lower than those observed using glucose, but the paramylon contents were similar between the two groups
The specific growth rate (SGR) increased in the order of glucose, lactate, and ethanol, showing a trend similar to that observed with biomass and paramylon production (Table 2)
The higher was the glucose concentration, the greater was the amount of total nitrogen (TN) consumed and the lower was the SGR (Table 2)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Microalgae have attracted attention as a promising source for carbon dioxide (CO2 ). Utilization and, recently, as raw materials for functional foods. E. gracilis, a fast-growing microalgal species, can produce value-added materials, including immune-functional paramylon (β-1,3-glucan). Higher amounts of paramylon can accumulate under heterotrophic and mixotrophic conditions in the presence of organic carbon than under photoautotrophic conditions [1]. The use of the carbon source for cultivation is expensive and may account for 50% of the total medium cost [2]
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