The development of efficient, environmentally friendly, low-cost approaches used to boost the growth of microalgae is urgently required to meet the increasing demands for food supplements, cosmetics, and biofuels. In this study, the growth promotion effects of protocatechuic acid (PCA) in the freshwater microalga Euglena gracilis were confirmed for the first time. PCA is a simple phenolic compound derived from natural plants and has a range of biological functions. The highest biomass yield, 3.1-fold higher than that of the control, used at 1.3 g·L−1, was obtained at 800 mg·L−1 of PCA. The yields of the metabolites chlorophyll a, carotenoids, and paramylon in the presence of PCA at 800 mg·L−1 were 3.1, 3.3, and 1.7 times higher than those of the control group, respectively. The highest paramylon yield was achieved at a lower dosage of PCA (100 mg·L−1), which is considered to be feasible for economic paramylon production. The growth and biosynthesis of metabolites stimulated by phytochemicals such as PCA could be an efficient and cost-effective strategy to enhance the productivity of microalgae in large-scale cultivations.
Euglena gracilis which could produce valuable metabolites is considered as promising feedstock for various industrial applications. Growth stimulation of microalgae culture with additives are cost-effective and simple approach to improve its productivity. Effect of vanillin, one of the most abundant phenolic compounds from lignocellulosic hydrolysate to E. gracilis was investigated. Vanillin showed hormesis effect to E. gracilis, growth promotion at lower concentration but inhibition at higher concentration. At optimal dosage of 10 mg/L vanillin, the biomass production of E. gracilis was enhanced by 36.5% and metabolites content such as chlorophyll, carotenoids also increased. From the high throughput analysis using fourier transform infrared spectroscopy, total lipid production will be simultaneously enhanced without sacrificing cell growth.
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