Cellulosic ethanol production on temperature-shift simultaneous saccharification and fermentation using the thermostable yeast Kluyveromyces marxianus CHY1612.

In cellulosic ethanol production, use of simultaneous saccharification and fermentation (SSF) has been suggested as the favorable strategy to reduce process costs. Although SSF has many advantages, a significant discrepancy still exists between the appropriate temperature for saccharification (45-50 °C) and fermentation (30-35 °C). In the present study, the potential of temperature-shift as a tool for SSF optimization for bioethanol production from cellulosic biomass was examined. Cellulosic ethanol production of the temperature-shift SSF (TS-SSF) from 16 w/v% biomass increased from 22.2 g/L to 34.3 g/L following a temperature shift from 45 to 35 °C compared with the constant temperature of 45 °C. The glucose conversion yield and ethanol production yield in the TS-SSF were 89.3% and 90.6%, respectively. At higher biomass loading (18 w/v%), ethanol production increased to 40.2 g/L with temperature-shift time within 24 h. These results demonstrated that the temperature-shift process enhances the saccharification ratio and the ethanol production yield in SSF, and the temperature-shift time for TS-SSF process can be changed according to the fermentation condition within 24 h.

Development and economic analysis of bioethanol production facilities using lignocellulosic biomass.

An integrated process for bioethanol production from Miscanthus sacchariflorus was used to construct a bench-scale plant constructed and an economic analysis was carried out to investigate the feasibility of its application to a commercial plant. The bench-scale plant was operated for 1 month and an economic analysis and sensitivity analysis was performed on the data acquired. In this study, 100,000 kL of bioethanol could be produced annually from 606,061 tons of M. sacchariflorus and the production cost was calculated to be US$1.76/L. However, the by-products of this process such as xylose molasses and lignin can be sold or used as a heat source, which can decrease the ethanol production costs. Therefore, the final ethanol production cost was calculated to be US$1.31/L, and is considerably influenced by the enzyme cost. The results and data obtained should contribute to the development of a commercial-scale lignocellulosic bioethanol plant.