A two stage pretreatment process to maximise recovery of sugars from cotton gin trash

We evaluated a two stage pretreatment process for liberation of sugars from cotton gin trash (CGT) for ethanol production. The 1st stage releases C5 sugars for propagation of yeast inoculum intended for C6 sugar fermentations. The effects of a range of dilute acid hydrolysis pretreatment conditions on CGT were assessed. Propagation of recombinant Saccharomyces cerevisiae GSF335 in 1st stage liquors yielded up to 66 g yeast biomass kg−1 CGT. In the presence of PEG 6000, 2nd stage pretreated fibres were highly acquiescent to enzyme hydrolysis, yielding up to 242 g glucose kg−1 CGT. We conclude that the optimum conditions for recovery of sugars from CGT are: 1:6 solids to liquids ratio with 12% H2SO4 wt. on solids at 180 °C for 15 min during the 1st stage, with the ensuing pressed unwashed fibre heated to 200 °C for 5 min during the 2nd stage.