Nutrients and COD removal of swine wastewater with an isolated microalgal strain Neochloris aquatica CL-M1 accumulating high carbohydrate content used for biobutanol production

In this study, a carbohydrate-rich microalga Neochloris aquatica CL-M1 was adapted to grow in swine wastewater. The effects of cultivation conditions (i.e., temperature, light intensity or N/P ratio) on COD/nutrients removal and carbohydrate-rich biomass production were investigated. The results indicate that the highest COD removal (81.7%) and NH3-N removal (96.2%) was achieved at 150 mu mol m(-2) s(-1) light intensity, 25 degrees C and N/P ratio = 1.5/1. The highest biomass concentration and carbohydrate content was 6.10 g L-1 and 50.46%, respectively, when N/P ratio = 5/1. The resulting carbohydrate-rich microalgal biomass was pretreated and used as a feedstock for butanol fermentation. With the initial sugar concentration of 48.7 g L-1 glucose and 3.4 g L-1 xylose in the pretreated biomass, the butanol concentration, yield, and productivity were 12.0 g L-1, 0.60 mol mol(-1) sugar, and 0.89 g L-1 h(-1), respectively, indicating the high potential of using Neochloris aquatica CL-M1 for butanol fermentation. (C) 2017 Elsevier Ltd. All rights reserved.