engleski

Bioethanol production from dilute acid pre-treated wheat straw hydrolisate using genetically engineered Saccharomyces cerevisiae

Lignocellulose is a potential raw material for sustainable production of biofuels and biochemicals, but to use lignocellulose in bioprocesses it is necessary to convert cellulose and hemicellulose to fermentable sugars. In this work the results of wheat straw pre-treatment with 2% H3PO4, in high-pressure reactor at different temperatures (160°C - 200°C) and retention times (1 min – 10 min), are shown. During dilute acid pre-treatment hemicellulose is degraded to pentose sugars that cannot be used by industrial ethanol producing yeasts. Therefore, to improve overall bioprocess efficiency a genetically engineered Saccharomyces cerevisiae strain, that can utilize xylose, was used. Fermentations were performed on different hydrolysates in shake-flasks, and in horizontal rotating tubular bioreactor. Efficiencies for fermentations carried out in shake flasks were in the range from 19.6% to 74.5%. The maximum efficiency of 88.2% was achieved during fermentation in HRTB. The acquired results were also used for life cycle analysis of the ethanol production process. For the quantification of process sustainability, specific partial area atot was calculated using SPIonExcel program. Value of atot represents environmental impact, and economic and ecological sustainability. The partial specific area for this ethanol production process is 7782.06 m2 for 1 kg of ethanol produced, that is 2-3 times lower compared to, a simultaneous saccharification and fermentation process (SSF) described in Morikawa [1] atot=21401.5 m2, and a separate enzymatic hydrolysis and fermentation process (SHF) presented in Saha [2] atot=16701.9 m2.

dilute acid pre-treatment ; wheat straw ; bioethanol ; Saccharomyces cerevisiae ; life cycle analysis

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