Isolation of bacterial strains able to metabolize lignin from screening of environmental samples

Abstract

Aims: To develop a method to detect bacteria from environmental samples that are able to metabolize lignin. Methods and Results: A previously developed UV-vis assay method for lignin degradation activity has been developed for use as a spray assay on agar plates. Nine mesophilic strains were isolated using this method from woodland soil incubated in enrichment cultures containing wheat straw lignocellulose: four Microbacterium isolates, two Micrococcus isolates, Rhodococcus erythropolis (all Actinobacteria) and two Ochrobactrum isolates (Alphaproteobacteria). Three thermotolerant isolates were isolated from the same screening method applied at 45°C to samples of composted wheat straw from solid-state fermentation: Thermobifida fusca and two isolates related to uncharacterized species of Rhizobiales and Sphingobacterium (Bacteroidetes), the latter strain showing tenfold higher lignin degradation activity than other isolates. The isolated strains were able to depolymerize samples of size-fractionated high molecular weight and low molecular weight Kraft lignin, and produced low molecular weight metabolites oxalic acid and protocatechuic acid from incubations containing wheat straw lignocellulose. Conclusions: A new method for the isolation of bacteria able to metabolize lignin has been developed, which has been used to identify 12 bacterial isolates from environmental sources. The majority of isolates cluster into the Actinobacteria and the Alphaproteobacteria. Significance and Impact of the Study: Lignin-degrading bacterial strains could be used to convert lignin-containing feedstocks into renewable chemicals and to identify new bacterial lignin-degrading enzymes.

Microbial Mechanisms Mediating Increased Soil C Storage under Elevated Atmospheric N Deposition

“…The Micrococcaceae are represented on the microarray by genes encoding muconate-lactonizing enzymes that are involved in the breakdown of ligninderived aromatics in soil. Taylor et al (49) isolated two members of the Micrococcaceae able to grow on minimal medium containing lignocellulose, and they metabolized Kraft lignin into lowermolecular-weight products. Even though actinobacteria are not the primary agents of the later stages of plant litter decay, the changes in actinobacterial functional-gene composition observed here, occurring concomitantly with a decreased fungal presence, could be a mechanism responsible for lower decay under experimental N deposition.…”

Identification of Manganese Superoxide Dismutase from Sphingobacterium sp. T2 as a Novel Bacterial Enzyme for Lignin Oxidation

“…9 The presence of an extracellular superoxide dismutase enzyme is unusual, since bacterial superoxide dismutases are usually intracellular, 13 however an extracellular MnSOD enzyme has been reported in Streptococcus pyogenes, 29 which shares 42% and 48% sequence identity with SpMnSOD1 and SpMnSOD2 respectively. Database searches using the BLAST algorithm (see Supporting Information Figures S25, S26) reveal that homologues for SpMnSOD1 and SpMnSOD2…”

Biodegradation as natural fibre pre-treatment in composite manufacturing

“…The XRD spectra of the wheat straw before and after degradation ( Figure 3) show a sharp peak at 2q = 26°, a broad peak at 2q = 19 and a small peak at 2q = 41°, which can be attributed to the crystallographic planes (200), (1)(2)(3)(4)(5)(6)(7)(8)(9)(10) and (110) and (004) of crystalline cellulose I. 49,50 As it can be seen, the degradation/ extraction process does not induce the structural transformation of cellulose I (parallel orientation of chains) to cellulose II (antiparallel orientation of chains), unlike the mercerisation process for example, 51 suggesting that the fermentation of the biomass appears to be a mild pre-treatment technique.…”