Surfactants as fungal parasite control agents in oleaginous microalga, Graesiella sp. WBG-1, mass culture

Abstract

Microbial contamination is a devastating threat to the success of oleaginous microalgae mass cultivation. Fungal parasites are likely to infect cultivated microalgae, greatly reducing algal biomass to extremely low levels. In the present study, four surfactants were used to control fungal parasites in the culture of the oleaginous microalga, Graesiella sp. WBG-1, for the first time. In lab-scale experiments, 10–70 mg L−1 sodium dodecylbenzene sulfonate (SDBS) and coconut diethanolamide (CDEA) completely prevented fungal parasite infection. Moreover, SDBS had no adverse influence on the final biomass, lipid contents, and fatty acid profiles of Graesiella sp. WBG-1. Additionally, pilot-scale and industrial-scale experiments clearly confirmed that 10 mg L−1 SDBS effectively prevented fungal parasite infections without negatively affecting biomass and lipid contents. Furthermore, the lipid contents of Graesiella sp. WBG-1 reached >30%, both in 200 m2 and 1000 m2 open raceway ponds. The practical SDBS approach demonstrated here can be inexpensively applied on pilot- (0.7 USD for a 40,000 L reactor) and industrial- (3.6 USD for a 200,000 L reactor) scales. Therefore, SDBS may be a desirable fungal parasite control agent in industrial scale cultivation of Graesiella sp. WBG-1 and, possibly, other oleaginous microalga. This effective and low cost approach advanced the prospect of using oleaginous microalgae as an economically viable strategy for the biodiesel production.