Comparison of fermentation strategies for ethanol production from olive tree pruning biomass

Olive tree pruning is a widely available and low cost lignocellulosic residue generated every year, being a potential source for bioproducts and renewable fuels production. In this context, this work has as main objective to propose an efficient scheme for the production of second generation ethanol from olive tree pruning biomass, focusing on the evaluation of different detoxification strategies (activated carbon, ammonium hydroxide and overliming) of the liquid fraction obtained after pretreatment, as well as different configurations of enzymatic hydrolysis and fermentation (including hydrolysis and sequential or simultaneous fermentation, pre-saccharification or co-fermentation) of the pretreated olive tree pruning solid. The best results of each fraction were tested in slurry, at varying initial solid loadings and aeration levels. The use of NH4OH 5N as a detoxification method and the pre-saccharification and co-fermentation configuration without aeration are proposed, resulting in 13.86 g ethanol/100 g raw material after 46 h of process.