Abstract: Worldwide corn production is continuously increased in order to satisfy the growing demand for more food. However this leads to the production of a large amount of solid wastes that either left in the field or at best used as animal feed of low quality. In the present study a more sustainable exploitation of corn wastes (especially corn stem) was studied. Firstly corn stem biomass was effectively pretreated using NaOH solution, in order to improve its structure for the following acidogenic fermentation. The effect of alkaline pretreatment on biomass structure (using scanning electron microscopy and porosimetry) and on biomass lignin content was also evaluated. The anaerobic acidogenic fermentation experiments of the pretreated corn stem biomass were carried out using an up-flow anaerobic sludge blanket reactor (UASB) culture, either as free cells or immobilized on corn cob and kissiris. In all cases the immobilized cells increased the organic acids yields during the acidogenic fermentation. The main organic acids produced were lactic, acetic and butyric acid. The organic acids could be subsequently used either as chemicals or as substrate for the production of ester-based biofuels, as a cost-effective and environmentally friendly alternative for second generation biofuels production.
Keywords: corn stem, lignocellulose, organic acids, acidogenesis, alkaline pretreatment, bet, sem, lignin