Application of sodium erythorbate to promote the growth of Chlorella vulgaris

Abstract

Sodium erythorbate (NaE) is a common antioxidant in food processing. In this study, the abilities of NaE to reduce photosynthetic oxygen accumulation in culture medium and improve microalgal growth were evaluated using the green microalga Chlorella vulgaris and glucose as a reference. NaE (from 2.0 to 16.0 g L−1) led to a lower accumulation of dissolved oxygen (DO) in a concentration-dependent manner. A significant negative correlation (p < 0.05) between the optical density (OD680) and DO level suggested that algal growth was promoted by NaE through depleting oxygen in the medium. After 12 days of cultivation, maximum OD680 and biomass were obtained with a NaE dosage of 8.0 g L−1 (respectively, 3.99 and 6.26 times greater than in the control without NaE). Compared with this dosage group which maintained an appropriate low DO level (2 to 6 mg L−1), higher dosage groups showed relatively little growth promotion due to an insufficiency of DO (<2 mg L−1). When glucose was added into mixotrophic systems for C. vulgaris, to the same total carbon amount as NaE, DO fell rapidly to less than 2 mg L−1 owing to its greater consumption (43.9%) compared to that of NaE (16.7%). Furthermore, in the NaE treatment, the pigment contents, cell density, and algal biomass were, respectively, 4.17 to 4.44 times, 2.67 times, and 1.21 times greater than in the glucose treatment. These findings indicate that algal autotrophic growth could be enhanced effectively by NaE through the moderate control of DO.