Study On Low-cost Alkaline Pretreatment For Improving Enzymatic Hydrolysis Rate Of Corn Stover

The utilization of renewable lignocellulosic biomass to produce fuel ethanol has been widely applied in response to the increasingly serious energy shortages and environmental pollution problems. The enzymatic conversion of lignocellulosic biomass to fermentable sugars is difficult as its complex structure. An effective pretreatment method is required to improve the utilization rate of lignocellulosic biomass. Alkali pretreatment, which can utilize pulping equipment, showed a satisfactory performance. However, sodium hydroxide pretreatment has many limitations, such as high cost, chemicals is difficult to recycle, which affect the economical performance of the bioconversion of corn stover. This study presents corn stover pretreatments using sodium carbonate(Na2CO3) combined with oxygen and cotton pulping black liquor to improve the efficiency of the biomass-to-sugar conversion.First, the pretreatment of corn stover is sodium carbonate combined with oxygen with different total titratable alkali, oxygen pressure, and temperature. The influences of pretreatments on solid yield, delignification and carbohydrate recovery under different pretreatment conditions were investigated and then enzymatic hydrolysis with a cellulase loading of 20FPU/g substrate, β-glucosidase loading of 10IU/g substrate, xylanase loading of 5U/g substrate for 48 h. The effect of pretreatment was evaluated by enzymatic efficiency and the final sugar yield. The optimum pretreatment were obtained through those experiments, as follows: the total titratable alkali of 25%, oxygen pressure of 0.6 MPa, and temperature of 160°C. Under those conditions, the solid yield was 52.82%, the removal of lignin was 79.23%, the recovery rate of glucan and xylan is 91.11% and 62.53%, the enzymatic hydrolysis rate of glucan and xylan is 87.10% and 70.74%, and the total sugar yield was 75.16%.Waste liquid from cotton pulping mill as pretreatment chemicals to treat corn stover and investigate its effect on improving enzymatic digestibility of corn stover. This study presents corn stover pretreatments using CPBL in combination with Na OH or Na2SO3 to improve the cost-effectiveness of the biomass-to-sugar conversion. The results showed that 78.37%, 74.94% and 82.09% of the lignin was removed after pretreatment with sodium hydroxide(SHP), CPBL(CPBLP) and CPBL combined with sodium sulfite(SS-CPBLP). Accordingly, the glucose and xylose contents in the pretreated corn stover increased to more than 56% and 21% after CPBLP and SS-CPBLP, respectively, which was comparable to SHP. Moreover, the total sugar yield of CPBLP and SS-CPBLP was 66.44% and 75.32%, which was 2.9% and 11.8% higher than that of SHP(65.05%), respectively. The lignin content in the black liquor rose from 6.9g/L to 17.8g/L, and the sulfonation degree of the black liquor reached 0.8mmol/g after SS-CPBLP. The results indicate that the use of CPBL for corn stover pretreatment not only efficiently produced fermentable sugar products, but also presented a solution to the CPBL pollution issue. Thus, this process represents amethod of waste recycling with high industrialization potential.