Lignocellulolytic systems of soil bacteria: A vast and diverse toolbox for biotechnological conversion processes

Lignocellulose from plant biomass represents an abundant and renewable source for the production of environmentally friendly chemicals and biofuels. However, its recalcitrant nature entails the use of complex biochemical reactions that are still challenging. Since the degradation of lignocellulose is the current bottleneck of the conversion processes, the search for novel enzymes and microbial strains for degrading plant biomass is of high importance. Currently, bacteria are in the spotlight as promising candidates for novel conversion strategies due to their wide functional diversity and versatility. Here, we review the lines of evidence that show the high potential of bacterial strains from soil for biomass conversion ranging from strain characterization to metagenome and metatranscriptome analysis. Substantial and diverse fractions of soil bacteria are able to decompose the major lignocellulose components. To do that, bacteria evolved structurally variable and often highly complex lignocellulolytic systems composed of enzymes as well as proteins involved in efficient substrate binding. Both as individual components or in combination, bacterial enzymes, and accessory proteins appear to be promising tools in the biotechnological valorization of lignocellulose.