Functioning of a synthetic lignocellulolytic microbial consortium: The effect of conditions on dynamics of interactions and functioning

The rich polysaccharide sugar content (75%) of lignocellulosic biomass (LCB) makes it a perfect resource for production of liquid fuels and industrial building blocks. Various LCB-degrading microbial consortia from different sources, with a set of “core” strains, have drawn attention. In particular, a bacterial-fungal consortium denoted SWT, consisting of two bacteria (Citrobacter freundii so4 and Sphingobacterium sp. w15) and one fungus (Coniochaeta sp. 2T2.1) has shown superior LCB degradation performance when growing on wheat straw (WS). This thesis starts with an overview (Chapter 1) of microbial LCB degradation processes and a summary of previous studies, with a focus on LCB-degrading microbial consortia and relevant enzyme families. To disentangle the mechanisms of bacterial-fungal synergisms in the SWT consortium, we set out to use genome and metabolic potential analyses (Chapter 2); compare the transcriptomes of strain 2T2.1 growing alone or in the SWT consortium on wheat straw (WS) (Chapter 3); examine the effect of abiotic conditions on bacterial-fungal synergisms and degradation performance (Chapter 4); examine the transcriptome profiles of both bacteria and fungal strain 2T2.1 at different conditions over time (Chapter 5); and analyze the identity of bacterial strain w15 (Chapter 6). The here-studied bacterial-fungal consortium showed great potential to serve as a model for the functioning of LCB-degrading consortia, with diverse functions assigned to each member strain: the main degrader Coniochaeta sp. 2T2.1, hemicellulose degradation assistant S. paramultivorum w15, and the system helper C. freundii so4. The excellent enzymatic potential of this consortium can be further explored for microbial biotechnology developments.