Bacterial Synergism in Lignocellulose Biomass Degradation – Complementary Roles of Degraders As Influenced by Complexity of the Carbon Source

Abstract

Lignocellulosic biomass (LCB) is an attractive source of carbon for the production of sugars and other chemicals. Due to its inherent complexity and heterogeneity, efficient biodegradation requires the actions of different types of hydrolytic enzymes. In nature, complex microbial communities that work efficiently and often synergistically accomplish degradation. Studying such synergisms in LCB degradation is fundamental for the establishment of an optimal biological degradation process. Here, we examine the wheat straw degradation potential of synthetic microbial consortia composed of bacteria and fungi. Growth of, and enzyme secretion by, monocultures of degrader strains were studied in aerobic cultures using wheat straw as the sole carbon and energy source. To investigate synergism, co-cultures were constructed from selected strains and their performance was tested in comparison with the respective monocultures. In monoculture, each organism – with a typical enzymatic profile – was found to mainly consume the cellulose part of the substrate. One strain, Flavobacterium ginsengisoli so9, displayed an extremely high degradation capacity, as measured by its secreted enzymes. Among 13 different co-cultures, five presented synergisms. These included four bacterial bicultures and one bacterial–fungal triculture. The highest level of synergism was found in a Citrobacter freundii/Sphingobacterium multivorum biculture, which revealed an 18.2-fold increase of the produced biomass. As compared to both monocultures, this bacterial pair showed significantly increased enzymatic activities, in particular of cellobiohydrolases, mannosidases, and xylosidases. Moreover, the synergism was unique to growth on wheat straw, as it was completely absent in glucose-grown bicultures. Spent supernatants of either of the two partners were found to stimulate the growth on wheat straw of the counterpart organism, in a directional manner. Thus, the basis of the LCB-specific synergism might lie in the specific release of compounds or agents by S. multivorum w15 that promote the activity of C. freundii so4 and vice versa.

Metabolic Exchange with Non-Alkane-Consuming Pseudomonas stutzeri SLG510A3-8 Improves n -Alkane Biodegradation by the Alkane Degrader Dietzia sp. Strain DQ12-45-1b

“…Until now, almost all success stories about the rational design of microbial communities for efficient microbiological processes are based on the following two strategies. The first one is the aggregation method, in which every member could accomplish the tasks of its synthetic microbial consortium but with underperforming efficiencies (39,40). The second strategy is the "division-oflabor" approach, in which the individual constituents perform complementary roles (41)(42)(43).…”

Genomic analysis of a lignocellulose degrading strain from the underexplored genus Meridianimaribacter

“…and Chryseobacterium sp. isolated from decaying wood were recently found to be able to produce lignocellulolytic enzymes to degrade wheat straw [17,18]. Other members of Cytophaga-Flavobacteria for instance Zhouia, Aquibacter, Flavimarina,…”

Soil Aggregate Microbial Communities: Towards Understanding Microbiome Interactions at Biologically Relevant Scales

“…organisms can have nonadditive effects on geochemical cycles such that functional responses to perturbations in the environment are more than the sum of individual microbial parts; synergistic or competitive interactions between taxa can affect metabolic functions relative to organisms grown in isolation. For example, microbial cocultures can degrade lignocellulosic biomass more efficiently than the same species in monoculture, with degradation efficiencies found to increase as much as 18-fold in coculture relative to the constituent monocultures (29). This phenomenon is well known from studies of bulk sediment and lab cultures, but less is known about how community interactions drive the nuances of geochemical cycling within structured environments like soil aggregates.…”