Tuesday, May 3, 2011
Sweetgum, Liquidambar styraciflua L., grows as understory in southeastern U.S. pine plantations and is eradicated through herbicide applications. Instead of being a nuisance, this fast growing hardwood understory could become an important source of biomass for the southeastern U.S. biochemical-based biorefineries. Heartwood and bark from sweetgum could be used as feedstock. Unfortunately, sweetgum bark is recalcitrant to biochemical-based processes. This research examined the release of carbohydrates from sweetgum bark at higher temperatures and with an improved enzyme cocktail. Ground sweetgum bark was pretreated in 1% dilute acid at 160 °C for 60 min in non-stirred batch reactors and hydrolyzed with Accellerase 1500® for 24 hr; this resulted in the recovery of 12.6 mg glucose per g of ground bark. As an alternative treatment, sweetgum bark was treated in 85 °C water in a shaking water bath for 18 hr prior to the pretreatment and enzymatic hydrolysis described above. This additional treatment resulted in the recovery of 22.7 mg glucose per g of ground bark. In addition to be a better pretreatment of the biomass, the 85 °C water extract inhibited the growth of Listeria innocua and E. coli O157:H7, as indicated by zones of inhibition. In sum, the ground feedstock treating step coupled to dilute acid pretreatment and enzymatic hydrolysis increased the glucose recovery; and, the water extract contained value-added compounds that may increase the overall profitability of a biorefinery that is using sweetgum as a feedstock.