Abstract: In order to enrich the germplasm resources of the high-quality lignin degrading strains,alkali lignin was used as the sole growth carbon source and a bleaching/dyeing method with two kinds of lignin analogues Azure-B and Remazol Brilliant Blue was subsequently used to isolate and screen a bacterium with ability to degrade lignin from dropped leaves-covered soil. 16S rRNA gene sequence analysis was to identify this bacterium,ultraviolet spectrophotometry was applied to determine the activities and their variation trends of lignin peroxidase （LiP）,manganese peroxidase（MnP）,and laccase（Lac）,and the scanning electron microscopy（SEM）was used to observe their morphological changes during degradation. A functional bacterium was successfully isolated and designated as Erwinia sp. QL-Z3. The QL-Z3 grew to stable phase after 48 h incubation in liquid alkali lignin medium,OD₆₀₀ reached 0.31. The degradation rate of lignin reached 14.23% after 72 h incubation. The enzymatic activities related to lignin degradation reached to peak values at 48 h and 60 h：Mnp reached 263.83 U/L after 60h fermentation,and Lip and Lac reached 104.11 U/L and 77 U/L respectively after 48 h fermentation. SEM results demonstrated that the strain depolymerized the lignin sample,destroyed the lignin structure and broke it into small fragments. This work systematically reveals that the strain Erwinia sp. QL-Z3 has an effective lignin degradation performance,and it can be a potential candidate for lignin biodegradation.

Key words: alkali lignin, lignin degrading bacteria, Erwinia