Effect of non-thermal plasma process on biomass, lipid, fatty acid and lignocellulosic material of Scenedesmus microalga for biofuel production

Abstract

Abstract This study assessed the effect of short-period (3 min.) application of non-thermal plasma (NTP) on the synthesis of biomass and lipids in Scenedesmus sp. as well as determine fatty acid content, elemental composition and lignocellulosic material. We also investigated the long-period (10 min.) exposure of microalgal biomass to NTP prior to lipid extraction. After subjecting the Scenedesmus biomass for short-period of plasma process, the maximum lipid productivity (20.6 mg L-1 day-1) was achieved on the fourth day of cultivation, with high percentages of saturated fatty acids notably palmitic acid (C16:0). Results of elemental composition (C, N, O, Na, Mg, Si, K, Ca) in Scenedesmus biomass showed that NTP application does not change these chemical compounds in algal biomass, while the lignocellulosic material such as cellulose content doubled (29.3%) of almost twice the value of the control sample (14.5%), which is associated with depolymerization of the D-glucose units mediated by NTP. After exposing the algal biomass for long-period of NTP as a pre-treatment method, the lipid recovery from Scenedesmus sp. ranged from 15.0 to 32.8% and decreased in the following order NTP (air + argon) ˃ sonication ˃ NTP (argon) ˃ NTP (air) ˃ control. These results suggest that NTP is a promising technology to not only induces lipid synthesis in microalgal cells but also to enhance the lipid recovery prior to lipid extraction, which can be converted into biodiesel. The lignocellulosic material in Scenedesmus biomass delignified by NTP can be also used to obtain second-generation bioethanol.