Use of Olive Mill Wastewater as a substrate for laccase production by fungi

The annual Olive oil production in Mediterranean countries is estimated to over 95% of world cultivation. Nevertheless, this process generates large amounts of wastes including Olive Mill Wastewaters (OMW) with approximately 3* 107 m3 per year which poses a critical problem for the environment due to their colossal concentration of salinity, organic matter, and phenolic compounds responsible for the phytotoxicity and microbial growth inhibitory effects. For these reasons, most attention has been agreed to determine the best strategy to reduce the phenol content of OMW. Laccases were recognized as the main enzymes implicated in the degradation of phenolics in OOW alongside this the use of halotolerant fungi offers potential applications for the production of enzymes able to retain good activity in saline environments. This work aimed to investigate the ability of halophilic fungi isolated from saline soil to produce laccase and degrade OMW on the agar plate method. For this purpose, 23 strains of fungi are isolated from the sebkha’s soil of Ain’Ezzmoul, Algeria on PDA plates. The same medium supplemented with Guaiacol was used to investigate the laccase production. Then the three positif laccasic strains obtained (GS7, GS15, and VS1) were examined for their ability to grow and decolorize OMW. Therefore, three phasic OMW were collected and prepared with several concentrations and solidified with 2% Agar. The strains GS7, GS15, and VS1 respectively were able to grow at OWW up to 50 %, 40 %, and 100 % but only GS15 showed a complete decolorization halo. This latter was tested to laccase production on OMW liquid medium and shows enzyme activities 114.90 U and 170.83 U on respectively 10% and 20% of unsupplemented OMW.