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Author(s): Teresa M. Mata
Tomás F. Tavares
Sónia Meireles
Nídia S. Caetano
Title: Bioethanol from brewers' spent grain: Pentose fermentation
Issue Date: 2015
Abstract: This work aims to perform a preliminary optimization of the fermentation of brewers' spent grain (BSG) sugarsto bioethanol, focusing on the pentose sugars. Firstly, it was conducted the acid pre-treatment and enzymatichydrolysis for studying different reaction times and amounts of enzymes in order to convert cellulose andhemicelluloses into simple sugars. The greatest amount of total sugars achieved experimentally is 5.56 g/ 25 gof dry BSG, corresponding to a sugars maximum conversion of 22.24 % from a BSG sample with about 6 %cellulose and about 40 % hemicelluloses. This was obtained by sequentially adding the acids HCl and HNO3with 1 wt% of concentration to BSG to perform the pre-treatment, simultaneously with 1.0657 g of Glucanex100g and 2.0 mL of Ultraflo L for the hydrolysis. Secondly, it was studied the fermentation step, using bothsynthetic medium and BSG hydrolyzate, and the yeasts Pichia stipitis NCYC 1541 (P. stipitis) andKluyveromyces marxianus NYCY 2791 (K. marxianus). Results show that the fermentation efficiency of allsugars in the synthetic media is higher than 80_% for both yeasts, but in the BSG hydrolyzate it is just 45.10 %for P. stipitis and 36.58 % for K. marxianus for a 72 h fermentation time at a 30 °C temperature. The theoreticalethanol yield from BSG hydrolyzates is 0.27 and 0.19 g ethanol/ g of sugars for respectively, P. stipitis and K.marxianus, but the actual ethanol yield obtained in this work is 0.0856 and 0.0308 g ethanol/ g of sugars,respectively that is three times smaller than the theoretical yield for P. stipitis and six times smaller for K.marxianus, which can be attributed to the presence of inhibitors resulting from the previous steps.
Related Information: info:eu-repo/grantAgreement/FCT - Fundação para a Ciência e Tecnologia/Projetos Estratégicos/UID/EQU/00511/2013 - POCI-01-0145-FEDER-006939/Laboratório de Engenharia de Processos, Ambiente, Biotecnologia e Energia/LEPABE
Document Type: Artigo em Revista Científica Internacional
Rights: restrictedAccess
Appears in Collections:FEUP - Artigo em Revista Científica Internacional

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