Evaluation of Alkaline Delignification (Naoh) of Açaí Seeds (Eutherpe Oleracea) Treated with H₂so₄ Dilute and Effect on Enzymatic Hydrolysis

Abstract

Ethanol production from lignocellulosic residues from agriculture, such as the acaí seeds, have a fundamental step, delignification. This step becomes is more effective when performed in combination with others pre- treatments, preferably with those that are able to remove the hemicellulose fraction, such as treatment with dilute sulfuric acid. The aim this work was perform the delignification of açaí seeds pretreated with dilute sulfuric acid and evaluate the enzymatic hydrolysis rate. The açaí sees were pretreated with 1 % sulfuric acid, 10% solids for 60 minutes at 121 °C. An experimental set 22 for evaluate delignification was performed and the experimental conditions were 1 % NaOH, temperature from 39.64 to 110.36 °C (+a; - a) and solids loading from 3.79 to 46.21 % (-a; +a). After delignification the liquid fraction was characterized for carbohydrate content, lignin and fermentation inhibitors (acetic acid, furfural and HMF). And solid fraction was also characterized for the carbohydrate, lignin and acetic acid. Both fractions were characterized via HPLC. After delignification, the resulting material was enzymatically hydrolyzed with an enzyme loading of 15 FPU/g of seed and 25CBU/g of seeds and 3% of solids and glucose concentrations were measured via HPLC. The results showed that the yield varied from 24 to 49% and delignification was effective in removing up to 89 % of this pre-treated material with dilute sulfuric acid lignin. The condition of 75°C and 3.79 % of solids was the condition that promoted higher enzymatic conversion with a value of 94.76%. It can be concluded that the conditions for delignification studied were effective in removing lignin and improve glucose release during enzymatic hydrolysis.