Abstract
Here, we investigated how different plant biomass, and—for one substrate—pH, drive the composition of degrader microbial consortia. We bred such consortia from forest soil, incubated along nine aerobic sequential - batch enrichments with wheat straw (WS1, pH 7.2; WS2, pH 9.0), switchgrass (SG, pH 7.2), and corn stover (CS, pH 7.2) as carbon sources. Lignocellulosic compounds (lignin, cellulose and xylan) were best degraded in treatment SG, followed by CS, WS1 and WS2. In terms of composition, the consortia became relatively stable after transfers 4 to 6, as evidenced by PCR-DGGE profiles obtained from each consortium DNA. The final consortia differed by ~40 % (bacteria) and ~60 % (fungi) across treatments. A ‘core’ community represented by 5/16 (bacteria) and 3/14 (fungi) bands was discerned, next to a variable part. The composition of the final microbial consortia was strongly driven by the substrate, as taxonomically-diverse consortia appeared in the different substrate treatments, but not in the (WS) different pH one. Biodegradative strains affiliated to Sphingobacterium kitahiroshimense, Raoultella terrigena, Pseudomonas putida, Stenotrophomonas rhizophila (bacteria), Coniochaeta ligniaria and Acremonium sp. (fungi) were recovered in at least three treatments, whereas strains affiliated to Delftia tsuruhatensis, Paenibacillus xylanexedens, Sanguibacter inulus and Comamonas jiangduensis were treatment-specific.Electronic supplementary materialThe online version of this article (doi:10.1007/s00248-015-0683-7) contains supplementary material, which is available to authorized users.
Highlights
Wheat straw (WS), corn stover (CS), and switchgrass (SG) constitute excellent sources of lignocellulose with high potential for the production of useful compounds such as biofuel, polyolefin-based plastics and lactic acid
The quantitative PCR (qPCR) measurements revealed the copy numbers of the bacterial 16S rRNA gene to vary from 5.05 ±1.17× 108 mL−1 (CS) to 9.22 ±0.21×108 mL−1 (WS1) after growth, whereas these were 1000-fold lower at the onset of each growth step
The abundances of fungal propagules showed larger variation across transfers and treatments ranging from 6.94 ±3.84×105 (WS2) to 8.18 ±5.30×107 ITS1 copies mL−1 (WS1) (Fig. 1b)
Summary
Wheat straw (WS), corn stover (CS), and switchgrass (SG) constitute excellent sources of lignocellulose with high potential for the production of useful compounds such as biofuel, polyolefin-based plastics and lactic acid. One may surmise that WS, CS, and SG substrates potentially require diverse specialized combinations of microorganisms for its deconstruction [6, 30, 37, 39]. It is currently accepted that proper biodegradation of lignocellulosic substrates requires a complex set of enzymes. Peroxidases, laccases, endoglucanases, exoglucanases, β-glucosidases, fucosidases and xylanases [28, 40, 42], among other enzymes, may be required in different and fluctuating amounts and proportions. Recent work has focused on plant biomass degradation by microbial consortia on the premise that the expected diversity of the microbially - secreted enzymes will result in efficient degradation rates [34]. As a result, the microbial consortia may better withstand physiological fluctuations. Examining the microbial consortia bred on lignocellulosic
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