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Open Access Highly Accessed Research article

Isolation and characterization of novel bacterial strains exhibiting ligninolytic potential

Luaine Bandounas123, Nick JP Wierckx1345, Johannes H de Winde123* and Harald J Ruijssenaars134

Author Affiliations

1 B-Basic, Julianalaan 67, 2628 BC Delft, The Netherlands

2 Delft University of Technology, Department of Biotechnology, Julianalaan 67, 2628 BC Delft, The Netherlands

3 Kluyver Centre for Genomics of Industrial Fermentation, Julianalaan 67, 2628 BC Delft, The Netherlands

4 BIRD Engineering BV, Westfrankelandsedijk 1, 3115 HG Schiedam, The Netherlands

5 RWTH Aachen University, Institute of Applied Microbiology, Worringerweg 1, 52056 Aachen, Germany

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BMC Biotechnology 2011, 11:94  doi:10.1186/1472-6750-11-94

Published: 13 October 2011

Abstract

Background

To expand on the range of products which can be obtained from lignocellulosic biomass, the lignin component should be utilized as feedstock for value-added chemicals such as substituted aromatics, instead of being incinerated for heat and energy. Enzymes could provide an effective means for lignin depolymerization into products of interest. In this study, soil bacteria were isolated by enrichment on Kraft lignin and evaluated for their ligninolytic potential as a source of novel enzymes for waste lignin valorization.

Results

Based on 16S rRNA gene sequencing and phenotypic characterization, the organisms were identified as Pandoraea norimbergensis LD001, Pseudomonas sp LD002 and Bacillus sp LD003. The ligninolytic capability of each of these isolates was assessed by growth on high-molecular weight and low-molecular weight lignin fractions, utilization of lignin-associated aromatic monomers and degradation of ligninolytic indicator dyes. Pandoraea norimbergensis LD001 and Pseudomonas sp. LD002 exhibited best growth on lignin fractions, but limited dye-decolourizing capacity. Bacillus sp. LD003, however, showed least efficient growth on lignin fractions but extensive dye-decolourizing capacity, with a particular preference for the recalcitrant phenothiazine dye class (Azure B, Methylene Blue and Toluidene Blue O).

Conclusions

Bacillus sp. LD003 was selected as a promising source of novel types of ligninolytic enzymes. Our observations suggested that lignin mineralization and depolymerization are separate events which place additional challenges on the screening of ligninolytic microorganisms for specific ligninolytic enzymes.