Stoichiometric Conversion of Cellulosic Biomass by in Vitro Synthetic Enzymatic Biosystems for Biomanufacturing

Abstract

Cellulosic biomass is the earth’s most abundant renewable resource, which is considered to be a promising feedstock for manufacturing biofuels and biochemicals. In this study, stoichiometric enzymatic phosphorolysis of cellulosic biomass for manufacturing biochemicals or biofuels by in vitro synthetic enzymatic biosystems was designed. Three cascade phosphorolytic enzymes, cellodextrin phosphorylase, cellobiose phosphorylase, and polyphosphate-dependent glucokinase, were used for the biotransformation of cellodextrins to high-energy phosphorylated sugars (that is, glucose 1-phosphate and glucose 6-phosphate). A series of downstream exergonic reactions then converted these high-energy phosphorylated sugars into myo-inositol, resulting in a near-stoichiometric conversion of cellodextrins with a high product yield of 98% (w/w). Moreover, this enzymatic biosystem can even work for the acid-treated biomass hydrolysate containing microorganism-toxic compounds. The construction of this in vitro synthetic enzymatic biosystem provided an alternative method for the utilization of cellulosic biomass rather than cellulolytic enzyme hydrolysis to fermentative monomeric sugars followed by microorganism fermentation, showing potentials in the production of biocommodities such as hydrogen, rare sugars, and electricity from cellulosic biomass.