Second generation bioethanol production from orange peel waste
Author(s)
Santi, Guglielmo
Date Issued
March 29, 2012
Type
Doctoral Thesis
Abstract
The present PhD thesis was aimed at assessing the feasibility of second generation bioethanol production from a few food-processing lignocellulosic residues.
To this purpose, three residues (orange peel waste, olive pomace and grape pomace) were chemically characterized and orange peel waste (OPW) appeared to be the most promising matrix, the total fermentable sugars amounting up to about 48% of the dry matter.
A novel lab-scale direct steam injection apparatus was used to perform an acid-catalyzed steam-explosion (ACSE) pretreatment of the selected matrix under four temperature-time conditions. The performance of the ACSE pretreatments was also compared with that of a conventional autoclave.
ACSE pretreatments at 200 °C for 90 s and 180 °C for 150 s led to the highest pectin solubilization (about 73%) with a positive effect on the subsequent enzymatic hydrolysis step, performed with a commercial cellulase.
The highest depolymerization yield (about 57%) was obtained from the solid pretreated at 180 °C for 150 s.
The resulting hydrolyzate was efficiently fermented by the industrial strain S. cerevisiae F15 in the shaken-flask scale under repeated-batch conditions.
To scale-up the previous results, a new ACSE trial at 180 °C for 90 s was performed by tripling the solid loading, and the entire process feasibility was assessed at the bench-reactor scale.
On the basis of a mass balance including all the glucose and fructose (11.13% dm) released after pretreatment at 180 °C for 150 s at triple solid loading and the glucose freed after enzymatic hydrolysis (17.86% dm), and accounting for an overall ethanol yield of 41.5%, the overall process yield at the bench-reactor scale would amount to about 153 L bioethanol per metric ton dry OPW.
Additional information
Dottorato di ricerca in Biotecnologia degli alimenti
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