346 / 2018-07-31 16:08:20

A new-developed pretreatment method of the concentrated phosphoric acid plus hydrogen peroxide (PHP) for bioethanol production from lignocellulosic biomass

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Concentrated phosphoric acid plus hydrogen peroxide (PHP) was attempted for pretreating lignocellulosic biomasses for facilitating the enzymatic hydrolysis and subsequent ethanol conversion. Results indicated that 71-96% lignin and more than 95% hemicellulose in various feedstocks (agricultural residues, hardwood, softwood, bamboo, and their mixture, and garden wastes mixture) can be removed. Consequently, higher than 90% glucose conversion of the feedstocks after PHP pretreatment indicated its flexibility to different feedstocks. Moreover, 2 typical feedstocks of wheat straw and oak chips were PHP-pretreated with different sizes, the average glucose conversion reached 94.9% and 100% with lower coefficient of variation (7.9% and 0.0%), suggesting PHP-pretreatment can significantly weaken the negative effects of feedstock sizes on subsequent conversion. the representative feedstock of wheat straw was optimized for the pretreatment conditions, as well as the enzymatic hydrolysis and simultaneous saccharification and fermentation at high solid loading. Results indicated that the optimized pretreatment conditions were 40°C, 2.0 h, and H3PO4 proportion of 70.2% (H2O2 proportion of 5.2%), by which glucose yielded 299 mg/g wheat straw (946.2 mg/g cellulose) after 72 h enzymatic hydrolysis. The pretreated wheat straw at these conditions was employed for hydrolysis at solid loadings, results indicated solid loading could reach 20% with 77.4% cellulose-glucose conversion and glucose concentration of 164.9 g/L in hydrolysate, it even was promoted to 25% with only 3.4% decrease on cellulose-glucose conversion. 72.9% cellulose-glucose conversion still was achieved as the minimized input CTec2 of 20 mg protein/g cellulose was employed for hydrolysis at 20% solid loading. Maximal ethanol conversion of 88.2% and ethanol concentration of 69.9 g/L were obtained after 120 h SSF at solid loading of 15.3%, and CTec2 enzyme and yeast were in lower input of 13.2 mg protein/g cellulose and 1.0 g/L, respectively. Consequently, 15.5 g ethanol was harvested from 100 g wheat straw (dry basis) at the optimal conditions. The obtained results above suggested the great potential of PHP pretreatment on bioethanol production from lignocellulosic biomass in application.