Effects of Tryptophan Along with Sodium Pyruvate and Sodium Thiosulfate on Chlorella vulgaris Growth

Microalgae could serve as an ideal bioenergy resource for third-generation biofuels because of its endless features. However, in an effort to render it as a commercially viable bioenergy resource, certain improvements that enhance its productivity are required. In the present study, the role of three independent substrates, tryptophan, sodium thiosulfate, and sodium pyruvate, and their incorporation in modified BG-11 towards maximizing the Chlorella vulgaris FACHB-8 productivity was studied. These substrates could strongly impart a stimulating effect on microalgal productivity, firstly, either by promoting faster growth and chlorophyll content (tryptophan), or secondly by quenching the reactive oxygen species out of the culture medium (pyruvate), or thirdly by reducing the culture medium (thiosulfate). Response surface mediated optimal design model was effective in calculating the optimal concentration of these three independent substrates in modified BG-11. The observed actual values (1.54 g L⁻¹—biomass and 1.91 µg L⁻¹—chlorophyll) of the model were in close agreement with the predicted values (1.4 g L⁻¹—biomass and 1.82 µg L⁻¹—chlorophyll), thus, indicating the validity to the model. Tryptophan (2.2 times-chlorophyll and 2.5 times-biomass) was most effective in stimulating microalgal growth as compared with other substrates in modified BG-11. This study supported the concept that tryptophan after following one of the three pathways acted as the precursor for the production of indole acetic acid that in turn acted as a phytostimulator for microalgal growth. The outcomes of the present study would offer a step towards resolving the gaps present in producing viable, sustainable, high chlorophyll producing microalgal biomass. Effects of tryptophan along with sodium pyruvate and sodium thiosulfate on Chlorella vulgaris FACHB-8 growth