Scale-up for esters production from straw whiskers for biofuel applications

•Scale-up of anaerobic acidogenesis of wheat straw by a UASB culture.•The process was promoted by culture immobilization on kissiris.•Organic acids were produced from straw without a separate hydrolysis step.•1-Butanol was the best solvent for acids recovery from the fermentation broth.•Enzymatic esterification of the acids with 1-butanol resulted to 90% yield. Delignified wheat straw was fermented by a mixed bacterial anaerobic culture obtained from a UASB reactor to produce organic acids (OAs). Kissiris was used as immobilization carrier in a 2-compartment 82L bioreactor filled with 17L of fermentation broth for the first 7 fermentation batches and up to 40L for the subsequent batches. The amount of straw used was 30g/L and the temperature was set at 37°C for all experiments. The total OAs reached concentrations up to 17.53g/L and the produced ethanol ranged from 0.3 to 1mL/L. The main OAs produced was acetic acid (6–8g/L) and butyric acid (3–8g/L). The OAs were recovered from the fermentation broth by a downstream process using 1-butanol, which was the solvent with the best recovery yields and also served as the esterification alcohol. The enzymatic esterification of OAs resulted to 90% yield.