Accelerated lipid production from distillery wastewater by Rhodosporidium toruloides using an open-bubble-column reactor under non-aseptic conditions

Abstract

It is an ideal and sustainable approach to recover renewable energy like biodiesel and to remove organic matters from wastewater simultaneously. However, the common demands of aseptic conditions and long reaction time limit the practical applications of this technology. In this study, lipid production by Rhodosporidium toruloides was investigated using distillery wastewater with an initial soluble chemical oxygen demand (SCOD) of 28,080–17,120 mg/L, an initial cell density of 0.5–2 × 108 cells/mL, and an aeration rate of 0.9–4.5 vvm (air volume/liquid volume/minute) in an open-bubble-column reactor at room temperature. The lipid production reached its peak of 1.92 ± 0.24 g/L in 12 h with a maximum lipid productivity of 160 mg/(L• h) achieved under the conditions: initial SCOD 20,315 mg/L, initial cell density 2 × 108 cells/mL and aeration rate 4 vvm, without external nutrients and sterilization. The associated removal efficiencies for SCOD, total phosphorus (TP) and total nitrogen (TN) were 71.82 ± 0.52%, 79.53 ± 1.77% and 54.39 ± 6.45%, respectively. Both contaminating bacteria and fungi were negligible throughout the cultivation period, suggesting that the studied process has good adaptability to full scale practical applications.