초록
<P><B>Abstract</B></P> <P>This study investigates ultrasonic enhancement of xylitol production from sugarcane bagasse using <I>C. tropicalis</I> MTCC 184 immobilized on PU foam. Initial xylitol yield of 0.53 g/g xylose improved to 0.65 g/g of xylose (in 36 h fermentation) after optimization of medium and fermentation parameters. Optimum values of experimental parameters for maximum xylitol were: yeast extract = 5.78 g/L, (NH<SUB>4</SUB>)<SUB>2</SUB>SO<SUB>4</SUB> = 3.22 g/L, KH<SUB>2</SUB>PO<SUB>4</SUB> = 0.58 g/L, MgSO<SUB>4</SUB>·7H<SUB>2</SUB>O = 0.57 g/L and temperature = 29.3 °C, initial pH = 6.2, agitation rate = 151 rpm and initial xylose concentration = 20.9 g/L. Application of 37 kHz sonication @10% duty cycle during fermentation at optimum conditions resulted in marked intensification of fermentation kinetics. Xylitol yield of 0.66 g/g of xylose has been obtained in ultrasound-assisted fermentation in just 15 h. Fitting of time profiles of substrates and products to kinetic model has highlighted actual physical mechanisms underlying 2-fold faster kinetics induced by sonication.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Optimum xylitol yield from bagasse using <I>C. tropicalis</I> on PU foam = 0.65 g/g of xylose. </LI> <LI> Significant medium components: yeast extract, MgSO<SUB>4</SUB>·7H<SUB>2</SUB>O, KH<SUB>2</SUB>PO<SUB>4</SUB> and (NH<SUB>4</SUB>)<SUB>2</SUB>SO<SUB>4.</SUB> </LI> <LI> Significant process parameters: temperature, pH, agitation and substrate concentration. </LI> <LI> Xylitol yield of 0.66 g/g of xylose in ultrasound-assisted fermentation in just 15 h. </LI> <LI> Application of sonication resulted in >2-fold enhancement of xylitol productivity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>