Impact of nitrogen source on laccase activity in water by spawn pellets of Pleurotus ostreatus (oyster mushroom) and applications for water treatment

Sammanfattning

Chemical pollution due to organic micropollutants results in a significant threat to aquatic ecosystems and human health. In addressing this challenge, bioremediation treatments by Pleurotus spp. based on oxidoreductase enzymes, including laccases, demonstrate potential for the removal of organic micropollutants from wastewater. This thesis aimed to study a spawn-based method for the production of laccase in water using the white-rot fungi P. ostreatus M2191. The study investigated the impact of two different spawn types, either grain-based or sawdust-based, and four nitrogen sources (ammonium nitrate, urea, yeast extract, wheat bran) on laccase activity in both experimental and literature studies. The research revealed that grain-based spawn resulted in significantly higher laccase activity compared to sawdust-based spawn. Among the nitrogen sources tested, yeast extract followed by wheat bran were the most effective in increasing laccase activity. The results indicated that P. ostreatus exhibits lower enzyme activity with inorganic nitrogen sources compared to organic nitrogen sources when subjected to submerged fermentation. The literature study demonstrated the variability in laccase production among Pleurotus spp. and strains for different nitrogen sources even when provided at the same concentrations. Thus, detailed studies on specific strains are needed to optimize laccase activity. This study contributes valuable insights toward developing a sustainable method for enzyme-based wastewater treatment by illustrating the influence of spawn type and nitrogen source on laccase activity.