Enhancement of sorghum biomass hydrolysis by addition of amylases to an ionic liquid-based deconstruction process

Conversion of lignocellulosic biomass to renewable biofuels and bio-based chemicals at scale holds great promise for increasing domestic supplies of energy and alternatives to petrochemicals but is contingent upon improvements in biomass deconstruction. Here we report a method to maximize the enzymatic hydrolysis of whole plant samples containing fibrous and non-fibrous carbohydrates in sorghum, a naturally drought-tolerant high-yielding bioenergy feedstock. This process involves the addition of amylases to ionic liquid-pretreated biomass in conjunction with traditionally employed cellulase and hemicellulase cocktails.

We found that amylases are compatible with cholinium-based ionic liquids and act synergistically with other saccharolytic enzymes to deconstruct sorghum biomass. By using mixtures of sorghum grain (high starch content) and stover (low starch content), we show that amylases can produce up to 4-fold higher glucose yields from biomass with a higher starch content but even samples containing only stover can benefit from amylase addition. Total monomeric sugar concentrations of 70 and 153 g/L were obtained from stover or grain biomass, respectively, when performing a reaction with 20% solids in presence of amylases. This study presents new possibilities for process intensification during the deconstruction of starch-containing bioenergy feedstocks.