The strain Klebsiella oxytoca THLC0409 was isolated from a lignocellulose-degrading microflora
and used in the direct conversion of Napiergrass powder to ethanol. Central Composite
Design (CCD), part of the Response Surface Methodology (RSM) was adopted to study the
effects of the fermentation time, the initial pH of the liquid medium, the cultivation
temperature, and the yeast extract (YE) concentration on ethanol production.Asecond-order
model that relates the ethanol concentration to four basic factors was developed. Regression
analysis revealed that the maximum ethanol concentration of 472 ppm could be reached at
a fermentation time of about 11 days, an initial pH of 7.04, a cultivating temperature of 31 C,
and a YE concentration of 7.0 g l1. The adjusted R-square of the regression model was 0.996,
indicating a good fit at 99.6% confidence level. The highest ethanol yield and productivity
were estimated to be 82 g kg1 and 360 mg kg1 h1, respectively.