Abstract
Second-generation biofuel production is in high demand, but lignocellulosic biomass’ complexity impairs its use due to the vast diversity of enzymes necessary to execute the complete saccharification. In nature, lignocellulose can be rapidly deconstructed due to the division of biochemical labor effectuated in bacterial communities. Here, we analyzed the lignocellulolytic potential of a bacterial consortium obtained from soil and dry straw leftover from a sugarcane milling plant. This consortium was cultivated for 20 weeks in aerobic conditions using sugarcane bagasse as a sole carbon source. Scanning electron microscopy and chemical analyses registered modification of the sugarcane fiber’s appearance and biochemical composition, indicating that this consortium can deconstruct cellulose and hemicellulose but no lignin. A total of 52 metagenome-assembled genomes from eight bacterial classes (Actinobacteria, Alphaproteobacteria, Bacilli, Bacteroidia, Cytophagia, Gammaproteobacteria, Oligoflexia, and Thermoleophilia) were recovered from the consortium, in which ~46% of species showed no relevant modification in their abundance during the 20 weeks of cultivation, suggesting a mostly stable consortium. Their CAZymes repertoire indicated that many of the most abundant species are known to deconstruct lignin (e.g., Chryseobacterium) and carry sequences related to hemicellulose and cellulose deconstruction (e.g., Chitinophaga, Niastella, Niabella, and Siphonobacter). Taken together, our results unraveled the bacterial diversity, enzymatic potential, and effectiveness of this lignocellulose-decomposing bacterial consortium.
Highlights
The growing demand for renewable fuels to search for less environmentally impacting solutions has been nursing biofuel production improvements
A flat and compact structure was observed without bagasse fiber peels, indicating that the autoclaving process did not interfere with the sugarcane bagasse fiber structure (Figure 2A,B)
Distinct bacterial morphological types are observed attached to the sugarcane fibers, suggesting that lignocellulosic deconstruction occurred through different microorganisms. These results strongly suggest that the bacterial consortium might be changing the lignocellulose fiber structure to use it as a carbon source
Summary
The growing demand for renewable fuels to search for less environmentally impacting solutions has been nursing biofuel production improvements. First-generation sugarcane ethanol has a relatively high yield, it can generate large amounts of lignocellulosic biomass or bagasse residues. This remaining biomass contains more than 65% of the plants’ fixed energy and is organized systematically through various polymers [1]. Lignocellulose can be partially deconstructed into fermentable sugars, increasing the overall fuel yield by its use in second-generation ethanol production [2,3,4]. Lignocellulosic biomass deconstruction still is a challenging process. The polymers found in the lignocellulosic biomass are mostly cellulose, hemicellulose, pectin, and lignin [5]. The most abundant organic polymer on Earth, is a linear
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