초록
The influence of aeration on ethanol production by Pichia stipitis was studied in wheat straw hydrolysates subjected to ozone pretreatment for the first time. In a first stage, different aeration rates ranging from 0.03 to 0.50L air/min, which corresponds to a volumetric oxygen transfer coefficient from 1.1 to 9.6h<SUP>-1</SUP>, were applied to model glucose/xylose substrates. The most promising value was found to be 3.3h<SUP>-1</SUP> (0.1L air/min) leading to better xylose utilization, an ethanol yield of 0.40g ethanol/g sugars and complete depletion of sugars at 72h. In a second stage, the effect of aeration was analyzed in ozonized wheat straw hydrolysates. Sugars were completely depleted at 96h and ethanol yield reached a value of 0.41g ethanol/g sugars. The addition of controlled oxygen (K<SUB>L</SUB>a=3.8h<SUP>-1</SUP>) enhances the efficiency of the process causing an increase of 29.1% in ethanol production and a considerable reduction of 42.9% in fermentation time as compared to non-aerated hydrolysates.