N2 periodic pulsation process intensification to improve ethanol productivity in solid state fermentation of steam-exploded corn stalk

Abstract

Long fermentation time and high oxygen partial pressure were significant challenges for high ethanol productivity in solid state fermentation (SSF). In this study, the feasibility of N2 periodic pulsation to improve ethanol productivity was investigated. Changes of CO2 concentration and water state distribution in N2 periodic pulsation SSF were examined. A metabolic flux model was developed to understand the effect of N2 periodic pulsation on ethanol production. The results indicated that ethanol productivity of 1.75 g/(L·h) in N2 periodic pulsation group (NPPG) was 34.4% higher than that in control group (CG) within 24 h. The maximum ethanol concentration and yield were 47.52 g/L and 70.80% at 70% moisture content, respectively. The CO2 concentration in NPPG was well below 5000 ppm at 21 h, which was much lower than 38,080 ppm in CG. Metabolic flux analysis revealed that the metabolic flux towards ethanol increased by 25% with the application of N2 periodic pulsation. These results confirmed that N2 periodic pulsation is an effective method for improving ethanol production in solid state fermentation.