Minimizing Wash Water Usage After Acid Hydrolysis Pretreatment of Biomass

Abstract Dilute acid pretreatment, needed to prepare biomass for saccharification, results in the production of a number of byproducts, which inhibit subsequent enzymatic hydrolysis and fermentation steps. In order to improve saccharification yields in the enzyme hydrolysis step, the pretreated biomass is often rinsed with room temperature water to remove these byproducts. High-density poplar was pretreated with 1% dilute sulfuric acid at 140 ºC for 40 minutes. After pretreatment the biomass was washed with water volumes equal to 0, 1 ½, or 3 times the biomass volume. The rinsed biomass was then enzymatically hydrolyzed and the concentrations of byproducts and resulting carbohydrates were quantified by high-pressure liquid chromatography (HPLC). Quantification was performed in pretreatment hydrolyzates, rinsing waters and enzyme hydrolyzates. Results show that inhibitory byproducts are highly soluble even in low amounts of wash water, and glucose yields are similar despite halving the amount of water used (3 and 1 ½ water volumes) in the wash step, signifying that the removal of a sufficient number of inhibitory compounds can be accomplished with even at small wash values. Specifically, enzymatic hydrolysis yielded between 3 and 4 grams glucose per gram dry biomass in the 1 ½ and 3 water volumes rinses, respectively, with totals at both conditions equaling between 7 and 8 grams glucose per gram dry biomass, respectively. The rinse step removed similar concentrations of inhibitors in either the 1 ½ and 3 water volume rinsing procedures

Storage of Round and Square Switchgrass Bales: Effect of Storage Time and Fungal Inoculation on Saccharification Efficiency

To produce fermentable sugars from lignocellulosic biomass feedstock, severe pretreatment conditions are needed (either high acid concentration, temperature, or retention times). High severities can produce toxic byproducts which inhibit enzymatic hydrolysis or fermentation. In order to reduce pretreatment severities (and thus increase enzyme and fermentation efficiency), the white-rot fungus Pleurotus ostreastus was seeded into square and round bales of Kanlow switchgrass (Panicum virgastum L.) and left in the field over a period of 9 month. The laccase producing fungus is believed to selectively degrade lignin, a common plant structural polymer, which can function as an enzymatic inhibitor. Samples were taken from different elevations within the bale 3, 5, 7, and 9 months after harvesting. These samples were treated at three different severities with liquid hot water pretreatment. Compositional analysis was done on the pretreated biomass, which was then enzymatically hydrolyzed with cellulases (endoglucanase and beta-glucosidase) after being washed. The yields (total recovered sugars over total present) were calculated and compared along five different variables: fungal treatment, storage time, pretreatment severity, sampling depth, and washing volumes. The results of the study found significant effects for sampling time (p=.0024) and pretreatment severity (

Switchgrass storage effects on the recovery of carbohydrates after liquid hot water pretreatment and enzymatic hydrolysis

Perennial grasses that would be used for bioenergy and bioproducts production will need to be stored for various periods of time to ensure a continual feedstock supply to a bioprocessing facility. The effects of storage practices on grass composition and the response of grasses to subsequent bioprocesses such as pretreatment and enzymatic hydrolysis needs to be understood to develop the most efficient storage protocols. This study examined the effect of outdoor storage of round switchgrass bales on composition before and after liquid hot water pretreatment (LHW) and enzymatic hydrolysis. This study also examined the effect of washing LHW pretreated biomass prior to enzymatic hydrolysis. It was determined that switchgrass composition after baling was stable. As expected, glucan and lignin contents increased after LHW due to decreases in xylan and galactan. Washing biomass prior to enzymatic hydrolysis reduced saccharification, especially in samples from the interior of the bale, by at least 5%

Switchgrass storage effects on the recovery of carbohydrates after liquid hot water pretreatment and enzymatic hydrolysis

Perennial grasses that would be used for bioenergy and bioproducts production will need to be stored for various periods of time to ensure a continual feedstock supply to a bioprocessing facility. The effects of storage practices on grass composition and the response of grasses to subsequent bioprocesses such as pretreatment and enzymatic hydrolysis needs to be understood to develop the most efficient storage protocols. This study examined the effect of outdoor storage of round switchgrass bales on composition before and after liquid hot water pretreatment (LHW) and enzymatic hydrolysis. This study also examined the effect of washing LHW pretreated biomass prior to enzymatic hydrolysis. It was determined that switchgrass composition after baling was stable. As expected, glucan and lignin contents increased after LHW due to decreases in xylan and galactan. Washing biomass prior to enzymatic hydrolysis reduced saccharification, especially in samples from the interior of the bale, by at least 5%