Progress Towards Engineering Microbial Surfaces to Degrade Biomass

Abstract

Lignocellulosic biomass is a promising feedstock to sustainably produce useful biocommodities. However, its recalcitrance to hydrolysis limits its commercial utility. One attractive strategy to overcome this problem is to use consolidated bioprocessing (CBP) microbes to directly convert biomass into chemicals and biofuels. Several industrially useful microbes possess desirable consolidated bioprocessing characteristics, yet they lack the ability to degrade biomass. Engineering these microbes' surfaces to display cellulases and cellulosome-like structures could endow them with potent cellulolytic activity, enabling them to be used in CBP. In this chapter, we discuss recent progress in engineering the surfaces of Saccharomyces cerevisiae, Escherichia coli, Bacillus subtilis, Corynebacterium glutamicum, and lactic acid bacteria. We discuss the techniques used to display cellulases on their surfaces, their recombinantly achieved cellulolytic activities, and current obstacles that limit their utility.

Stabilizing displayed proteins on vegetative Bacillus subtilis cells

“…Surface display methods are attractive because the microbe produces and displays the protein during growth, circumventing the need for time-consuming protein purification and immobilization procedures that are typically used to create protein coated materials (Garcia-Galan, Berenguer-Murcia et al 2011, Mohamad, Marzuki et al 2015, Hyeon, Shin et al 2016). Moreover, surface-engineered bacteria that display cellulolytic enzymes can be used as consolidating bioprocessing microbes that convert abundant plant biomass into biofuels and other biocommodities (la Grange, den Haan et al 2010, Olson, McBride et al 2012, Huang, Anderson et al 2014, Hyeon, Shin et al 2016, Huang and Clubb 2017). Gram-positive bacteria may be particularly well-suited for displaying heterologous proteins due to the relatively simple structure of their cell envelope, which consists of a single membrane surrounded by a thick peptidoglycan wall.…”

“…Several approaches have been developed to display heterologous proteins on the surface of vegetative B. subtilis (Kobayashi, Toida et al 2000, Desvaux, Dumas et al 2006, Nguyen and Schumann 2006, Chen, Wu et al 2008, Huang, Anderson et al 2014, Huang and Clubb 2017). These methods either covalently or non-covalently attach the protein to the cell wall peptidoglycan after it has first been exported across the membrane through the Sec translocon.…”