Engineering a cultivation strategy for higher lipid accretion and biodiesel production by the marine microalga Picochlorumsoloecismus

Abstract

Microalgal-derived biofuels are currently paving the way towards sustainable and green energy generation. The current study targets to bring in multiway novelties in this direction through generating substantial biomass and lipid yields in a single cultivation cycle, lower experimental time, less chemical utilization and enhanced biodiesel quality. It also ensures higher cost-effectivity, mass applicability and promising annual outcomes. In the present work, a marine microalga Picochlorum soloecismus was subjected to an extensive range of macronutrient stresses to elevate its storage lipids. Amongst all the factors studied, 4 best parameters, i.e., concentrations of NaCl and nitrate, initial culture pH, and incubation period were optimized and a modified medium called Optimized ASN (Artificial Seawater Nutrient) was developed. This resulted in 3.4- and 5.3-fold higher lipid content and productivity, reduction in the experimental time from 18 days to 9 days alongside a diminution of 350- and 25-fold in the requirements of chemicals - NaCl and NaNO3. The reduction in chemical uptake consequently lowered the medium cost by 16-fold. The biomass loss after optimization was almost insignificant and a single-phase cultivation cycle presented 2.8-fold higher lipid productivity than a two-phase cycle. The biodiesel properties were validated with the mandatory biodiesel standards. At a pilot-scale projection, the optimized medium approximated annual lipid productivity of 19.5 t ha−1 yr−1 generated through 35 annual cultivation cycles. Eventually, the medium was tested on 10 different freshwater and marine microalgae where the positive response showed by all the strains proved its suitability as an efficient lipid promoting culture medium with mass applicability.