Study of the Effect of Alkali Distillation Liquid on Simultaneous Saccharification and Co Fermentation (SSCF) of Alkaline Pretreated Solid State Fermented Sweet Sorghum Bagasse with Zymomonas Mobilis

Sweet sorghum is a promising energy crop to produce bioethanol. An integrated process is necessary to reduce the product cost and increase the utility efficient of feedstock. An alkaline pretratment combined distillation based on the advanced solid-state fermentation technology (ASSF) has been designed to improve the bioconversion of lignocellulose into fermentable sugar. After alkaline distillation step, most of lignin moved into aqueous state from lignocellulosic substrates. Effects of these alkali liquid on the performance of enzymatic saccharification and sugars fermentation of SS with Zymomonasmobilisis required to be investigated because it is important to decide the following process.

In this study, effects of lignin content, ionic strength, pH and washing operation on enzymatic saccharification and fermentation were studied. The results showed that: 1) The free lignin content has no obvious negative effect on enzymatic hydrolysis. 2) Ionic strength has no effects on enzymatic hydrolysis, but high ionic strength inhibits the fermentation of Zymomonasmobilis. 3) Final ethanol yield was highly dependent on the monomer sugar yields during prehydrolysis step in the present of various alkali distillation liquid concentration. 4) Highest ethanol yield was achieved when the solid from solid-liquid separation was washed once.