Orange peel pretreatment in a novel lab-scale direct steam-injection apparatus for ethanol production

Orange peel waste (OPW) was converted into ethanol by consecutive acid-catalysed steam-explosion (ACSE), enzymatic saccharification and fermentation with Saccharomyces cerevisiae F15. The first step was performed in the presence of 0.5% (volume fraction) sulphuric acid at a solid loading of 160 g L-1 using a novel laboratory-scale Direct Steam-Injection Apparatus under different reaction temperatures and times. ACSE at 200 degrees C for 90 s (or 180 degrees C for 150 s) yielded the highest solubilization of pectin (-73%) and a positive effect on the subsequent enzymatic hydrolysis step, that was carried out at 50 degrees C with an enzyme loading of 6 FPU g(-1) cellulose. OPW, pretreated at 180 degrees C for 150 s, yielded the highest glucose solubilisation degree (similar to 56%) at the end of the saccharification step, and the maximum ethanol yield coefficient (similar to 0.495 g g(-1)) and productivity (4.85 g L-1 h(-1)) at the end of the 3rd repeated fermentation batch in shaken-flasks. (C) 2013 Elsevier Ltd. All rights reserved.