Cotton ginning trash (CGT) collected from Australian cotton gins was evaluated for bioethanolproduction. CGT composition varied between ginning operations and contained high levels of extractives(26–28%), acid-insoluble material (17–22%) and holocellulose (42–50%). Pretreatment conditions of time(4–20 min), temperature (160–220 C) and sulfuric acid concentration (0–2%) were optimised using acentral composite design. Response surface modelling revealed that CGT fibre pretreated at 180 C in0.8% H2SO4 for 12 min was optimal for maximising enzymatic glucose recoveries and achieved yieldsof 89% theoretical, whilst the total accumulated levels of furans and acetic acid remained relativelylow at <1 and 2 g/L respectively. Response surface modelling also estimated maximum xylose recoveryin pretreated liquors (87% theoretical) under the set conditions of 150 C in 1.9% H2SO4 for 23.8 min. Yeastfermentations yielded high ethanol titres of 85%, 88% and 70% theoretical from glucose generated from:(a) enzymatic hydrolysis of washed pretreated fibres, (b) enzymatic hydrolysis of whole pretreatedslurries and (c) simultaneous saccharification fermentations, respectively.Crown Copyright 2014 Published by Elsevier Ltd. All rights reserved.
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