Effect of the nutrient composition on dye decolorisation and extracellular enzyme production by Lentinus edodes on solid medium

Abstract

The production of laccase and manganese peroxidase (MnP) by Lentinus edodes (Shiitake) was studied on a solid medium in conjunction with the decolorisation of the dyes Poly R-478, Remazol Brilliant Blue R (RBBR) and Orange II. L. edodes mycelium was able to decolorise all three dyes. Nitrogen (N) concentration-dependence studies with three N sources (ammonium chloride, peptone and malt extract) revealed that the range 1–3 mM N was optimum for both enzyme production and dye degradation, regardless of the N source or dye used. MnP production and the decolorisation of Poly R-478 and Orange II were inhibited completely above 8 mM N. The enzymatic processes also exhibited a Mn concentration dependence; 20 μM Mn proved optimum for dye decolorisation. The addition of natural supplements (oak sawdust and wheat straw) greatly enhanced MnP production. Oak sawdust had a positive effect on the decolorisation of each of the dyes investigated. A medium containing 10 g/l starch, 3.5 g/l malt extract and 20 g/l oak sawdust proved optimum for the enzymatic processes investigated.