(669f) Separate Hydrolysis and Fermentation of Untreated and Pretreated Miscanthus Cake to Produce Ethanol

Authors: 
Xiu, S., NC A&T State University
Shahbazi, A., North Carolina Agricultural and Technical State University

The use of lignocellulosic biomass to produce biofuel will add value to land and reduce emissions of greenhouse gases by replacing petroleum products. Valuable co-products derived from fractionation of miscanthus give the resulting fibrous fraction an economic advantage as a feedtock for ethanol production. Freshly harvestedmiscanthus from the North Carolina A and T farm was dewatered using press, whereby miscanthus is separated into a fiber-rich cake and a nutrient-rich juice.  The production of cellulosic ethanol from miscanthus fibers with or without alkali(NaOH) pretreatment were investigated by this work using separate hydrolysis and fermentation (SHF). The objective was to compare the effect of alkali pretreatment on the miscanthus samples with regards to ethanol yield.

 The pretreatment of miscanthus with NaOH was carried out to assess the effect of various NaOH concentrations on the enzymatic digestibility of the wet miscanthus cake. The concentrations of NaOH investigated were 0, 1, 4 and 7%, Enzymatic hydrolysis of the miscanthus cake was carried out using a cocktail of enzymes comprising of cellulase (NS 50013), β-glucosidase (NS 50010) and hemicellulose (NS 22002) at a temperature of 50oC for 96 hours. This was followed by fermentation using Escherichia coli (E. coli) at a temperature of 32oC, also for 96 hours.

 The hydrolysis products investigated using High Performance Liquid Chromatography (HPLC) included glucose, xylose, arabinose and uronic acids.  Samples were further analyzed for fermentation products including ethanol, glucose, xylose, arabinose and acetic acid. The results show a steady increase in fermentable sugars from the enzymatic hydrolysis over the time period, and also an increase in ethanol produced from the pretreated miscanthus as compared to the untreated miscanthus with the overall effectiveness of the alkali pretreatment being a function of the NaOH concentration. This suggests effective delignification leading to enhanced ethanol production.