Acetone-Butanol-Ethanol (ABE) fermentation with clostridial co-cultures for enhanced biobutanol production

Abstract

This study has addressed the issue of enhanced biobutanol production through Consolidated Bioprocessing, with the use of clostridial co-cultures combining C. acetobutylicum (Cac) and C. pasteurianum (Cpa). To begin with, the total Acetone-Butanol-Ethanol (ABE) solvent production and butanol selectivity of individual clostridial cultures grown on different carbon sources present in lignocellulosic hydrolysates. Thereafter, statistical optimization of ABE fermentation with co-culture system was carried out using Box-Behnken design. The optimization variables were Cac to Cpa inoculum ratio (X1 in mL mL−1), sodium concentration in the medium (X2 g L−1), and xylose/glucose ratio (X3 g g−1 L L−1), whereas response variables were butanol titre (Y1 in g L−1), biomass growth (Y2 OD600), total ABE titre (Y3 in g L−1). Maximum values of the response variables with the corresponding set of optimization parameters were as follows: Y1, max = 12.1 ± 0.45 (for X1 = 0.30, X2 = 5.90, X3 = 0), Y2, max = 4.15 ± 0.03 (for X1 = 0.3, X2 = 2.42, X3 = 0.14), Y3, max = 23.1 ± 0.55 (for X1 = 0.46, X2 = 6.36, X3 = 0). The study demonstrated a substantial ≈ 22% and 61% increment in butanol titre in co-culture system compared to individual fermentations with Cac and Cpa grown on pure glucose, respectively.