Isolation of Streptomyces sp. Strains Capable of Degrading Lignin Under Alkaline Conditions and Its Degradation Properties

Abstract

A bacterial strain (designated as Y-8), capable of efficiently degrading lignin under alkaline conditions, was isolated from saline-alkali soil and identified as Streptomyces sp. based on the morphological and physiological analyses as well as the gene sequences comparison of the 16 S rDNA. The alkali tolerance and lignin degradation capability of the isolated strain were determined. The results indicated that Streptomyces sp. Y-8 achieved the optimum lignin degradation at a temperature of 35 degrees C and a pH value of 9.5 with sucrose as the auxiliary carbon source and ammonium nitrate as the nitrogen source, reaching 32.6% in seven days. In addition, the activity of the three enzymes that were produced from the lignin degradation by Streptomyces sp. Y-8 under alkaline conditions (pH = 9.5), laccase (Lac), lignin peroxidase (Lip), and manganese peroxidase (MnP) was studied. The results indicated that the Lac and Lip activities reached their respective maximums on the fifth and fourth day of lignin degradation, respectively, being 4583.5 U/L, and 1163.2 U/L, respectively, and almost no MnP was detected throughout the process. This study is of great significance to the biological pretreatment of lignocellulose or the treatment of black liquid produced from papermaking under alkaline conditions.