Characterization and detoxification of enzyme hydrolysates derived from dilute ammonia pretreated sorghum bagasse

Lignocellulosic enzyme hydrolysate detoxification can be challenging because a balance between efficient detoxification strategies while avoiding sugar losses has to be met. In this study, milled Sorghum (Sorghum bicolor) bagasse was pretreated with ammonia (28% NH₄OH solution), and water at a ratio of 1:0.5:8 at 160^oC and 140-160 psi for 1h in a 300-mL pressure reactor. The pretreated sorghum was enzymatically hydrolyzed with different combinations of Spezyme^® CP, a cellulase and Novozyme 188, a β-glucosidase. Samples were collected at various time intervals (0-72h). Enzyme loading was based on the glucan content and mass of dry biomass (sorghum bagasse) added (g glucan/g dry biomass). A 5% biomass loading was used. The resulting enzymatic hydrolysate liquor (EHL_x) was analyzed for by- and degradation products. Organic acids, furaldehydes and phenolic acids were qualitatively and quantitatively detected through High Performance Liquid Chromatography (HPLC) - Diode Array Detector (DAD) method, developed for simultaneous and direct detection of EHL_x components. Monomeric and oligomeric sugars in the EHL_x were identified and quantified through an established HPLC-Refractive Index Detector (RID) method. Various detoxification strategies were evaluated.