UV-C-mediated lipid induction and settling, a step change towards economical microalgal biodiesel production†
Microalgae are highly efficient primary producers that can be grown in most types of water on non-arable land as a promising source of biofuel. However, large-scale microalgal biofuel production is currently uneconomical due to slow growth of high-percentage oleaginous algae and large harvesting costs. Here we present a new strategy, using a small dose of externally applied UV-C radiation, that significantly increases lipid contents of fast growing microalgae and that at higher doses also results in rapid settling. The procedure essentially separates biomass growth from lipid accumulation and harvesting which was tested in several microalgal strains and optimized to be completed within 48 h for Tetraselmis sp. using pilot-scale outdoor cultivation. This process resulted in a significant increase of both volumetric and areal lipid productivity with higher polyunsaturated fatty acid contents, while considerably reducing harvesting costs. Other benefits include control of co-cultured microbes and sanitized water for recirculation. UV-C-mediated lipid induction and settling (LIS) may contribute to commercial microalgal biofuel production.