Lignocellulose degradation with surface displayed enzymes on Pseudomonas putida.

Tozakidis IEP, Schulte MF, Pupkes H, Lenz F, Maas R, Jose J

Abstract

The economic conversion of lignocellulosic biomass represents an important milestone for the future bio-based industries [1]. Currently, major challenges lie in the variety of enzymes required, their large scale production and recycling at reasonable costs as well as their activities and stabilities. Here we present a whole-cell catalytic approach using the robust soil bacterium Pseudomonas putida as host for the surface display of cellulases [2] and hemicellulases [3]. Each 3 complementary enzymes were expressed as autotransporter fusion proteins and were shown to be located on the cell surface. The bacteria were able to hydrolyse their substrates when employed directly after cultivation, omitting any enzyme preparation or purification procedure. They could be applied at elevated temperatures of up to 55 °C over extended periods without losing structural integrity, allowing their simple separation and reuse in subsequent reaction cycles. A combination of P. putida cells, each displaying one type of cellulase, was applied on industrial cellulose residues, yielding glucose in a concentration of 700 µmol/L with an optical cell density of 10 after 24 hours. At these temperatures the cells did not consume the glucose, enabling its further downstream processing.