Abstract
The investigated integrated bioprocess for the production of bioethanol from lignocellulosic biomass, derived from the perennial herbaceous species Phalaris aquatica L., consists of three main stages, which were studied and optimised separately. The pretreatment process was investigated through a Taguchi statistical design where mild conditions were selected for the optimization of the hemicellulose hydrolysis. The solid residue, where cellulose lies, was enzymatically hydrolysed with the implementation of a Box-Denken statistical design and glucose was recovered at a concentration equal to 13.5 g/L. Glucose concentration increased to 45 g/L after the application of a semi-batch policy. The fermentation of the enzymatic hydrolysate with the yeast Saccharomyces cerevisiae was initially conducted under batch conditions in flask scale and the optimal regime was selected to be transferred to the bioreactor scale. Inoculum size, aeration, agitation speed, fermentation medium composition and type of strain were the parameters of study. The fermentation of the hydrolysate provided 47 g/L ethanol concentration under fed-batch conditions, corresponding to 90 % yield. The specific productivity was equal to 4.8 g/(L·h), while the overall productivity was maximized, through different feeding policies, to 2.3 g/(L·h).
