초록
<P>The feasibility of ethanol production using an enzymatic hydrolysate of pretreated cladodes of <I>Opuntia ficus</I>-<I>indica</I> (prickly pear cactus) as carbohydrate feedstock was investigated, including a comprehensive chemical analysis of the cladode biomass and the effects of limited aeration on the fermentation profiles and sugar utilization. The low xylose and negligible mannose content of the cladode biomass used in this study suggested that the hemicellulose structure of the <I>O</I>. <I>ficus</I>-<I>indica</I> cladode was atypical of hardwood or softwood hemicelluloses. Separate hydrolysis and fermentation and simultaneous saccharification and fermentation procedures using <I>Kluyveromyces marxianus</I> and <I>Saccharomyces cerevisiae</I> at 40 and 35 °C, respectively, gave similar ethanol yields under non-aerated conditions. In oxygen-limited cultures <I>K</I>. <I>marxianus</I> exhibited almost double the ethanol productivity compared to non-aerated cultures, although after sugar depletion utilization of the produced ethanol was evident. Ethanol concentrations of up to 19.5 and 20.6 g l<SUP>−1</SUP> were obtained with <I>K</I>. <I>marxianus</I> and <I>S</I>. <I>cerevisiae</I>, respectively, representing 66 and 70 % of the theoretical yield on total sugars in the hydrolysate. Because of the low xylan content of the cladode biomass, a yeast capable of xylose fermentation might not be a prerequisite for ethanol production. <I>K</I>. <I>marxianus</I>, therefore, has potential as an alternative to <I>S</I>. <I>cerevisiae</I> for bioethanol production. However, the relatively low concentration of fermentable sugars in the <I>O</I>. <I>ficus</I>-<I>indica</I> cladode hydrolysate presents a technical constraint for commercial exploitation.</P>