초록
<P><B>Highlights</B></P><P>► Alkali treatment of cotton stalks with 4% NaOH for 60min resulted in significant delignification. ► Hydrolysis of alkali-treated cotton stalk yielded 42.29g/L glucose and 6.82g/L xylose. ► SSF resulted in ethanol concentration and productivity of 19.48g/L and 0.41g/L/h, respectively. ► Thermotolerant <I>Pichia kudriavzevii</I> HOP-1 strain holds promise for commercial ethanol production.</P> <P><B>Abstract</B></P><P>In the present study, milled cotton stalks were subjected to alkali pretreatment with NaOH at 1–4% (w/v) concentrations at 121°C for time ranging from 30 to 90min. Ozone pretreatment was performed by passing 45mg/L of ozone gas over 2mm cotton stalks for 150min at a flow rate of 0.37L/min. The residual biomass from 4% alkali pretreatment for 60min showed 46.6% lignin degradation accompanied by 83.2% increase in glucan content, compared with the untreated biomass. Hydrolysis of 4% alkali-treated and ozone-treated cotton stalks was conducted using enzyme combination of 20 filter paper cellulase units/gram dried substrate (FPU/g-ds), 45IU/g-ds β-glucosidase and 15IU/g-ds pectinase. Enzymatic hydrolysis of alkali-treated and ozone-treated biomass after 48h resulted in 42.29g/L glucose, 6.82g/L xylose and 24.13g/L glucose, 8.3g/L xylose, respectively. About 99% of glucose was consumed in 24h by <I>Pichia kudriavzevii</I> HOP-1 cells resulting in 19.82g/L of ethanol from alkali-treated cotton stalks and 10.96g/L of ethanol from ozone-treated cotton stalks. Simultaneous saccharification and fermentation of the alkali-treated cotton stalks after 12-h pre-hydrolysis resulted in ethanol concentration, ethanol yield on dry biomass basis and ethanol productivity of 19.48g/L, 0.21g/g and 0.41g/L/h, respectively which holds promise for further scale-up studies. To the best of our knowledge, this is the first study employing SSF for ethanol production from cotton stalks.</P>