Chemo-microbial conversion of cellulose into polyhydroxybutyrate through ruthenium-catalyzed hydrolysis of cellulose into glucose.

Cellulose-derived glucose generated using the supported ruthenium catalyst was applied to poly(3-hydroxybutyrate) [P(3HB)] production in recombinant Escherichia coli. By the reaction with the catalyst at 220°C, 15-20 carbon mol% of cellulose was converted into glucose. The hydrolysate also contained byproducts such as fructose, mannose, levoglucosan, oligomeric cellulose, 5-hydroxymethylfurfural (5-HMF), and furfural together with unidentified compounds. Setting the reaction temperature lower (215°C) improved the ratio of glucose to 5-HMF, which was a main inhibiting factor for the cell growth. Indeed, the recombinant E. coli exhibited better performance on the hydrolysate generated at 215°C and accumulated P(3HB) up to 42 wt%, which was the same as the case of the same concentration of analytical grade glucose. The result indicated that the ruthenium-mediated cellulose hydrolysis has a potency as a useful biorefinery process for production of bio-based plastic from cellulosic biomass.