Different plastic-bag type photobioreactor for biomass production of Chlorella species

Abstract

Abstract Microalgae were generally recognized as safe and a promising source for proteins, polyunsaturated fatty acids, carbohydrates, and other bioactive substances in the industrial application such as foods, health supplements, biofuels, and pharmaceuticals. For mass production and cost down, plastic-bag has been utilized for microalgal growth. In this study, three plastic-bag types (plastic-bag, vertical plastic-bag, and horizontal plastic-bag) were designed to shape the liquid circulation for improving the mass transfer. Microalgae were cultivated under different weathers including the sunshine times and average global radiation as 46.7 h and 9.15 MJ/m2, 13.7 h and 4.8 MJ/m2, 38.2 h and 8.07 MJ/m2, and 37.1 h and 11.25 MJ/m2 for 15 days. The pH, biomass, and antioxidant of microalgae were further detected. The pH values of microalgae were ranged from 7.3–9.0 within 15 days cultivation. No obvious difference was present among these plastic-bags. Under low global radiation with the average 4.8 MJ/m2, the microalgal biomass produced by the vertical plastic-bag was 1.4-fold and 1.9 - fold higher than that of the plastic-bag and horizontal plastic-bag, respectively. This result suggested that the vertical plastic-bag photobioreactor had a high mass transfer with low shear stress. Furthermore, the antioxidant activity was assayed by the total polyphenol and total reductive capability. The result revealed that the microalgae contained 360.4 μg/L-culture corresponding to gallic acid using vertical plastic-bag, followed by horizontal plastic-bag with 289.6 μg/L-culture and plastic-bag with 230.6 μg/L-culture by the total polyphenol determination after 15 days cultivation. The similar result was also observed in the total reductive capability by vertical plastic-bag with 413.4 μg/L-culture corresponding to ascorbic acid, followed by horizontal plastic-bag with 373.2 μg/L-culture and plastic-bag with 353.7 μg/L-culture. Consequently, the vertical plastic-bag had the potential to be applied in the industrial field.