Ethanol production using pretreated biomass of Panicum maximum: effect of high solids loading on enzymatic hydrolysis and fermentation of hydrolyzates

Abstract

Despite the increasing number of studies on the production of ethanol using lignocellulosic biomass, the
process still has inconveniences due to the high costs associated with the biomass transformation steps,
such as enzymatic hydrolysis. One of the solutions to reduce them, consist of using a high solids loading
and a minimal enzyme doses in function of the pretreated biomass to hydrolyze. Due to the above, the
present study determined the effect of high solids loading on the enzymatic hydrolysis yield and the possible implications on a fermentation considering the detoxification of the hydrolyzates. Pretreated biomass of
Panicum maximum was used as a hydrolysis substrate. Initially, the adequate enzyme doses to hydrolyze
the pretreated biomass was selected with a subsequence evaluation of a fed-batch system dosing pretreated
biomass and enzymes. Finally, two detoxification methods were evaluated, overliming (NaOH) and
activated carbon, to determine the effect on the concentration of total sugars (AR) and the potential use
of the detoxified hydrolyzate as a carbon source for an alcoholic fermentation. The recommended doses
for the enzymatic hydrolysis was 61.44 BHU/g of cellulases complex and 1.77 CBU/g of -glucosidases
with a final total sugars concentration of 66.79 g/L after 48 h and a pretreated biomass concentration
of 20%w/w. Also, the detoxified hydrolyzate with overliming had the highest ethanol concentration and
productivity with a value of 19.43 g/L and 0.81 g/L/h, respectively.