Metagenomic investigation of bacterial laccases in a straw-amended soil.

BACKGROUND

Bacterial laccases play a crucial role in the degradation of lignin and the turnover of soil organic matter. Their advantageous properties make them highly suitable for a wide range of industrial applications. However, the limited identification of these potential enzymes has impeded their full utilization. The straw-amended soil provides materials for the development of bacterial laccases.

METHODS

Metagenomic sequencing of a straw-amended soil was conducted to explore novel bacterial laccases. The putative bacterial laccases were then screened using profile hidden Markov models for further analysis. The most abundant gene, , was heterologously expressed in and the recombinant laccase was purified for enzymatic characterization.

RESULTS

A total of 322 putative bacterial laccases were identified in the straw-amended soil. Among them, 45 sequences had less than 30% identity to any entries in the Carbohydrate-Active Enzyme database and only 4.66% were more than 75% similar to proteins in the NCBI environmental database, exhibiting their novelty. These enzymes were found across various bacterial orders, demonstrating substantial diversity. Phylogenetic analysis revealed a number of the bacterial laccase sequences clustered with homologs characterized by favorable enzymatic properties. Five full-length representative bacterial laccase genes were obtained by modified thermal asymmetric interlaced PCR. The laccase activity of lacS1 was validated. It was a mesophilic enzyme with alkaline stability and halotolerance, indicating its promise for industrial applications.

IMPLICATIONS

These findings highlight novel bacterial laccase resources with potential for industrial applications and enzyme engineering.