Improved Cellulosic Ethanol Titres from Highly Lignified Cotton Trash Residues Using Various Batch and Fed-Batch Process
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Improved Cellulosic Ethanol Titres from Highly Lignified Cotton Trash Residues Using Various Batch and Fed-Batch Process Configurations S. McIntosh 1 & J. Palmer 1 & M. Egbuta 2 & L. Liu 2 & Tony Vancov 1
# Crown 2019
Abstract This study investigates a fed-batch simultaneous saccharification fermentation (F-SSF) process to increase ethanol titres from highly lignified (41.6 wt.%) cotton gin trash residue. The optimal initial solid loading, enzyme dose, feed quantities and intervals to maximize substrate feed and subsequent ethanol titres were examined. Under batch SSF conditions, initial extracted cotton gin trash (ECGT) solid loadings were maximised at 19.35 wt.% and attained an ethanol titre of 23.3 g/l with a corresponding yield of 53.7%. Operating under optimised F-SSF mode, fermentations were initiated with 16.13 wt% EGCT solids followed by fresh ECGT feeds of 16.13 wt% and 12.9 wt.% at 12-h intervals. Cellulase levels were maintained at 44 FPU/g glucan throughout the fermentations. The final ethanol titre of 41 .4 g/l with a corresponding conversion rate of 70.1% was achieved after 72 h. Comparable ethanol yields of 40 g/l with 67.8% conversion were realized with lower cellulase dosing (25 FPU g/glucan) but only after extending the fermentation by 24 h. Keywords Cotton gin trash . Fed-batch SSF . High solid loading . Saccharomyces cerevisiae strain Fali®
Introduction Forecast decline in world oil reserves, growing demand for petroleum products, volatile crude oil prices and national energy security are major drivers for investing in alternative renewable transportation fuels [1]. The acknowledged impacts of fossil fuels on climate change and contribution to greenhouse gas (GHG) emissions further strengthen the need for renewable fuels [2]. Amongst these alternatives, ethanol from biomass feedstocks is regarded as a creditable substitute. One of the key barriers in cellulosic ethanol processing is overcoming the recalcitrant nature of the complex lignocellulosic matrix, for most part requiring several processing steps. In general, pretreatment of lignocellulose is a prerequisite to liberate Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12155-019-10023-8) contains supplementary material, which is available to authorized users. * Tony Vancov [email protected] 1
NSW Department of Primary Industries, Wollongbar Primary Industries Institute, 1243 Bruxner Highway, Wollongbar, NSW 2477, Australia
2
Southern Cross Plant Science, Southern Cross University, Lismore, NSW, Australia
cellulose from its lignin seal and disrupt its structure before effective enzymatic hydrolysis and subsequent fermentation can take place [3]. A range of chemical, physical and biological processes to release these sugars and transform them into ethanol have been configured, yet all face challenges of cost, technological breakthroughs and infrastructure needs [4]. Bioprocess strategies for the generation of fermentable sugars and transformation into ethanol can be achieved in two
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