Cellulosic processing trait development using a thermoregulated, intein-modified xylanase

Abstract

In planta consolidated bioprocessing has the advantages of decreasing biomass pretreatment costs, utilizing excess plant protein production capacity for enzyme production, and decreasing mass transfer resistance of enzyme diffusion to its substrate. However, in planta expression of cell wall degrading (CWD) enzymes often leads to detrimental plant phenotypes that impact crop yield. To provide in planta CWD enzyme activity without any adverse phenotype, a thermostable xylanase, XynB (EC 3.2.1.8), was engineered with a thermoregulated intein, Tth-HB27 DnaE-1 (Tth intein), that controls its hydrolytic activity through conditional intein splicing. Maize plants expressing the heat inducible Tth intein-modified XynB developed normally, yet possessed enhanced post harvest glucose production from dried corn stover. Expression of CWD enzymes as dormant, intein-modified proteins that can be activated by heat treatment after harvest provides the basis for developing a novel cellulosic processing trait in plants.