The Effect of Furan Extraction on the Ethanol Fermentability of Canarium schweinfurthii (African Elemi) Seed

Abstract

The potential of cellulosic ethanol as a panacea to environmental degradations associated with fossil fuel has recently spurred research on the technicalities to improve product yield amidst the myriad of inhibitors domicile in a lignocellulosic feedstock. The effect of the extraction of furan products on the fermentability of Canarium schweinfurthii (African Elemi) seeds was the focus of this research. Proximate characterization (PC), Fourier Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM) were applied to ascertain the level of the hydrolyzable components and the need for pretreatments on the substrate. The PC indicated a 55% hydrolyzable component, recalcitrating lignin at 29% and hemicelluloses above 15%. The PC, the FTIR, and the SEM results underscored the need for chemical pretreatments before the enzymatic hydrolysis and fermentation. One of the pretreatments was furan extraction in an atmospheric refluxing setup, targeted at getting rid of furan inhibition of fermentation and obtaining furfural and hydroxyl methyl furfural (HMF) as complementary products. The pretreatment extract was 72% HMF; the residue, along with the non-pretreated, the acid, and the alkaline pretreated, were subsequently hydrolyzed with three different crude enzymes from cellulosic fungal strains and a commercial enzyme from Trichoderma reesei. The GC/MS analysis revealed that the hydrolyzate from the furan extracted substrate was about 90% glucose, that of the non-pretreated was about 70% xylose. So, the furan extraction enriched the hexose compositions over the pentoses, and the hexose enrichment translated into more ethanol fermentability. The maximum ethanol conversion from the non-pretreated and the furan extracted substrates was 8.8 and 63%, corresponding to ethanol yield of 0.045 and 0.332 g ethanol/ g sugar, respectively. Moreover, the statistical analysis and the kinetics parameters of the fermentation affirmed that the furan-extracted substrates suffered less inhibition to cell growth and ethanol yield.