Optimizing the Pretreatment of Lignocellulosic Biomass

Alternative feedstocks should be explored to diffuse the food-versus-fuel conflict in using food crops such as corn for biofuel production. Utilizing non-edible plants, such as bamboo and switchgrass, which grow well on marginal lands, and agricultural waste, such as corn stover, is crucial to diffusing this conflict. In this work, we investigated various pretreatment methods to optimize fermentable sugar yields (glucose and xylose) from the enzymatic hydrolysis of bamboo, switchgrass, and corn stover to make them renewable carbon sources for biofuels and bioproducts. First, each biomass was ball-milled for 15 min and 30 min. Then, the 30-minute ball-milled samples were delignified using acetic acid and sodium chlorite. Finally, the delignified samples were then ball-milled for 30 min. All the samples were subjected to enzymatic hydrolysis using Cellic CTec2 cellulase enzymes in citrate buffer (pH 5.0) for 72 hours. The hydrolysates were analyzed using high-performance liquid chromatography at 24-hour time intervals. The results showed that increasing the ball milling time from 15 to 30 min increased the glucose and xylose concentrations. We also found that bamboo and corn stover yielded similar amounts of glucose and xylose, whereas switchgrass produced less fermentable sugars. Delignification of all the biomass resulted in slight increases in sugar yield. However, ball milling delignified samples increased the sugar yield by almost 2-fold. These results indicate that delignification followed by ball milling is the most effective method for increasing biomass sugar yield.