Testing of the new streptomyces strains for production of phenoloxidases

Abstract

Thirty wild new strains of filamentous bacteria belonging to the genus Streptomyces isolated from different Romanian soil samples and ten strains from Collection of microorganisms of Bioaliment Research Platform (acronym MIUG) were tested and screened for their ability to produce extracellular tyrosinase and laccase. Based on preliminary qualitative screening assays for the extracellular
phenoloxidases production carried out by stationary cultivation on Gause agar medium (GMA) supplemented with 1% (w/w) L-tyrosine, nineteen strains were selected as active producers. Furthermore, a quantitative selection based on active strains ability to produce tyrosinase and laccase by submerged cultivation in liquid Gause salts basal medium supplemented with 1 g L-1 L-tyrosine and 0.001 g L-1 CuSO4, during 168 hours was performed. Results showed that 70% of the Streptomyces strains have a good potential for producing tyrosinase and 30% of strains were remarked for their ability to produce laccase. Moreover, it was observed that, Streptomyces strains coded MIUG 4.89 and MIUG 4.88 from MIUG Collection have the ability to simultaneously produce both enzymes. The effect of temperature and pH on enzymes activity was also investigated. The optimum temperature for both activity (tyrosinase and laccase) was found to be 30°C. Laccase was found active over a pH range of 4.0 to 6.0 with maximum activity at pH 5.0. The optimum pH for tyrosinases activity was observed to be around 7.0. The obtained results are important for future applications of Streptomyces phenoloxidases in different areas.