Enhancement of lipid production and energy recovery from the green microalga Chlorella vulgaris by inoculum pretreatment with low-dose cold atmospheric pressure plasma (CAPP)

In the present study, a high-throughput procedure was employed to enhance biodiesel recovery from the green microalga Chlorella vulgaris through pretreatment of inoculum with low doses of cold atmospheric-pressure plasma (CAPP). Pretreatment for 30 s resulted in significant increase in the colony-forming unit (CFU) by 26.6% over the control, and recorded the highest biomass productivity of 0.193 g L-1 d(-1). In addition, the average cellular chlorophyll content was 18.7% and 23.3% higher than the control and 60 s, respectively. Moreover, short exposure times (30 and 60 s) significantly increased lipid content by 7.5% and 6.9%, respectively, over the control. Because 30 s pretreatment enhanced both growth and lipid content, the volumetric lipid productivity (40.7 mg L(-1 )d(-1)) increased by 16.6% and 17.6% over the control and 60 s, respectively. Interestingly, pretreatment for 60 s showed the maximum fatty acid methyl esters (FAMEs) recovery of 478.7 mg g(-1) dw, which confirms lipid accumulation in the form of glycerides due to plasma stress. Therefore, the maximum volumetric FAMEs production (998.1 mg L-1) was recorded in the culture inoculated with 60 s-exposed cells, which was 43.5% and 15.7% higher than that of the control and 30 s, respectively. Overall, pretreatment for 60 s resulted in the maximum gross energy output (GEO(Add)) of 10.70 kJ L-1, which was 79.5% higher than that of 30 s. In conclusion, the current study represents a novel approach for sustainable production of biodiesel from microalgae through inoculum exposure to a low-dose of CAPP.