Bioprocess intensification for acetone-butanol-ethanol fermentation from brewer's spent grain: Fed-batch strategies coupled with in-situ gas stripping

Abstract

A fed-batch ABE fermentation process coupled with in-situ gas-stripping to mitigate butanol toxicity was investigated. Two feeding strategies were compared: pulses of sugars and continuous feeding of the liquid released in the dilute acid pretreatment of brewer's spent grain. The concentrations of butanol (13.2 g L-1 total and 50 g L-1 average in the condensates for glucose pulse feeding) were higher than those obtained under batch conditions, showing that in-situ gas-stripping can relieve butanol toxicity. The continuous feeding of the fed-batch reactor produced similar butanol concentrations (10.2 g L-1 total and 65 g L-1 in the condensates), more stable concentrations of solvents in the condensates and enhanced monosaccharides uptake (99.1%) in comparison with the pulse feeding strategy. The efficient utilization of the enzymatic and pretreatment hydrolysates in the same fed-batch reactor is an integrated approach that could reduce capital and operating costs. The mathematical model proposed showed good performance to predict concentrations in the fermentation broth.