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A biorefinery concept for simultaneous recovery of cellulosic ethanol and phenolic compounds from oil palm fronds: Process optimization

Ofori-Boateng, Cynthia, Lee, Keat Teong, Saad, Bahruddin
Energy conversion and management 2014 v.81 pp. 192-200
Elaeis guineensis, antioxidants, bioethanol, biorefining, butylated hydroxytoluene, cellulose, enzymatic hydrolysis, fermentation, fronds, gallic acid, glucose, quercetin, sodium hydroxide, solvents, temperature, vanillic acid, wastes, xylose
In this study, process optimization of an ultrasonic-assisted organosolv/liquid oxidative pretreatment (SOP) of oil palm fronds (OPFs) for the simultaneous recovery of cellulose, bioethanol and biochemicals (i.e. phenolic compounds) in a biorefinery concept was carried out. The effects of time (30–60min.), temperature (40–80°C), NaOH concentration (1–5%) and sample:solvent ratio (1:10–1:50g/ml) on cellulose content, bioethanol yield and total phenolics contents (TPC) after SOP were investigated. At optimum conditions of pretreatment (i.e. 60°C, 40min, 3% w/v aq. NaOH and 1:20g/ml sample to solvent ratio), the recovered cellulose (55.30%) which served as substrate for enzymatic hydrolysis and subsequent fermentation yielded about 20.1g/l glucose, 11.3g/l xylose and 9.3g/l bioethanol (yield of 0.769g/g). The pretreatment liquor (mostly regarded as wastes) obtained at the optimum pretreatment conditions contained about 4.691mg gallic acid equivalent (GAE)/g OPFs of TPC, 0.297mg vanillic acid (VA)/g OPFs, 1.591mg gallic acid (GA)/g OPFs and 0.331mg quercetin (QU)/g OPFs. The pretreatment liquor was again analyzed to possess high antiradical scavenging activity (about 97.2%) compared to the synthetic antioxidant, 3,5-di-tert-butyl-4-hydroxytoluene (BHT) (80.7%) at 100ppm. Thus one sustainable way of managing wastes in biorefinery is the recovery of multi-bioproducts (e.g. bioethanol and biochemicals) during the pretreatment process.