Development of co-culture system for efficient production of biobutanol from eggplant stalk in the presence of a surfactant

The substrate and microbial diversity are major problems on biofuel production. In this context, limitations on biobutanol production from lignocellulosic wastes include low solvent production, the inhibitory effect of high substrate loading, and low sugar conversion. Therefore, this study suggests a co-culture strategy and a biodegradable surfactant to improve biobutanol production from eggplant stalk (ES). Some critical factors affecting the process such as fermentation time, initial ES loadings (5–20%), surfactant types (Tween 80, Triton X-100, and starch), different enzyme loadings (7.5–60 FPU/g_substrate cellulase enzyme), different yeast strains for co-culture with Clostridium beijerinckii DSMZ 6422 (Saccharomyces cerevisiae, Candida boidinii, and Kluyveromyces marxianus) were optimized. The highest total ABE and biobutanol concentrations were obtained as 15.66 g/L and 9.63 g/L using C. beijerinckii + C. boidinii co-culture in the presence of 20% ES pretreated with 15 FPU/g_substrate cellulase enzyme and 80 mg/g_cellulose starch. That means efficient ABE production and higher fermentable sugar recovery from ES were greatly aided by co-culture strategy and the use of starch as a biodegradable surfactant. The potential of ES, which was used as a raw material in biobutanol production for the first time in the literature, was further improved with the use of co-culture mode and a biodegradable surfactant.