Top-Down Enrichment Strategy to Co-cultivate Lactic Acid and Lignocellulolytic Bacteria From the Megathyrsus maximus Phyllosphere

Abstract

Traditionally, starting inoculants have been applied to improve ensiling of forage used for livestock feed. Here, we aimed to build up a bioinoculant composed of lactic acid-producing and lignocellulolytic bacteria (LB) derived from the Megathyrsus maximus (guinea grass) phyllosphere. For this, the dilution-to-stimulation approach was used, including a sequential modification of the starting culture medium [Man, Rogosa, and Sharpe (MRS) broth] by addition of plant biomass (PB) and elimination of labile carbon sources. Along 10 growth-dilution steps (T1–T10), slight differences were observed in terms of bacterial diversity and composition. After the sixth subculture, the consortium started to degrade PB, decreasing its growth rate. The co-existence of Enterobacteriales (fast growers and highly abundance), Actinomycetales, Bacillales, and Lactobacillales species was observed at the end of the selection process. However, a significant structural change was noticed when the mixed consortium was cultivated in higher volume (500ml) for 8days, mainly increasing the proportion of Paenibacillaceae populations. Interestingly, Actinomycetales, Bacillales, and Lactobacillales respond positively to a pH decrease (4–5), suggesting a relevant role within a further silage process. Moreover, gene-centric metagenomic analysis showed an increase of (hemi)cellulose-degrading enzymes (HDEs) during the enrichment strategy. Reconstruction of metagenome-assembled genomes (MAGs) revealed that Paenibacillus, Cellulosimicrobium, and Sphingomonas appear as key (hemi)cellulolytic members (harboring endo-glucanases/xylanases, arabinofuranosidases, and esterases), whereas Enterococcus and Cellulosimicrobium have the potential to degrade oligosaccharides, metabolize xylose and might produce lactic acid through the phosphoketolase (PK) pathway. Based on this evidence, we conclude that our innovative top-down strategy enriched a unique bacterial consortium that could be useful in biotechnological applications, including the development/design of a synthetic bioinoculant to improve silage processes.

Tracing the Century‐Long Evolution of Microplastics Deposition in a Cold Seep

“…Polymer‐degrading Pseudomonadales were the most dominant species. The bottom layer was primarily colonized by Lactobacillales , which exhibited the potential to biodegrade plastics, [ 55 , 56 ] and Hydra vulgaris , which produced a cellulolytic enzyme. [ 57 ] Cellulolytic enzymes are composed of a variety of complex enzyme systems, which can break the glycosidic bond and gradually hydrolyze macromolecular cellulose into glucose.…”

Enhancing plant growth promoting rhizobacterial activities through consortium exposure: A review

“…An innovative top-down strategy is developed by co-cultivation of LAB (Lactic acid bacteria) and LB (lignocellulolytic bacteria) populations by using a sequential and rational modification of MRS broth by overall dilution to stimulation approach ( Díaz-García et al, 2021a ). In this strategy, it is very important to manipulate the whole microbial consortium to obtain the desired function.…”

Merging Plastics, Microbes, and Enzymes: Highlights from an International Workshop

“…Recently, the degradation of PBAT by a marine microbial consortium showed that synergism and division of labor could be key mechanisms ( 86 ), similar to what is reported for lignin catabolism ( 87 ). Thus, the use of microcosms or enrichment liquid cultures could be excellent “top-down” strategies to select plastic-degrading microbial consortia (PDC) from environmental microbiomes ( 88 ). A proposed strategy to select PDC is the “dilution-to-stimulation” approach ( 89 ), where plastics (or their derived monomers) are used by the microbes as the sole carbon source.…”