Bioremediation of Olive Mill Wastewater (Zibar) using Phanerochaete chrysosporium and Potential use in Agriculture

Abstract

The manufacturing process of olive oil yields a black liquid waste called ‘olive mill wastewater’ (Zibar) creating a major environmental problem. Due to high levels of phytotoxic and antimicrobial compounds such as monomeric-polymeric phenols, volatile acids and polyalcohol, Zibar is toxic to plants and soil micro flora and can affect the soil quality. Proposed physio-chemical processes such as evaporation ponds or lagoons have not been efficient in decreasing the high toxicity of Zibar to reduce the ecological impact of Zibar, due to economic and technical reasons. Bioremediation using microorganisms is considered an environmentally compatible and least expensive altrantive. In this work, four fungal isolates were tested for their efficacy in reducing the total polyphenols from Zibar. Erlenmeyer flasks (125 ml) each containing 25 ml of Zibar were inoculated each with 5 PDA discs (7 mm grown with the fungi). The flasks were placed on a rotary shaker at 150 rpm for two weeks, at optimum temperature for each isolate. Before extraction of total polyphenols, fungal biomass was 2 removed by filtration. After that, 2.5 ml of treated Zibar was diluted to 50% with distilled water, acidified to pH 2.0 with 5M HCl and extracted with ethyl acetate (1:1, v/v), which was evaporated under fuming hood for 24h. The residue was dissolved in 2.5 ml methanol and the volume was completed to 25 ml with distilled water. Total phenol concentration was determined spectrophotometrically at 725nm using Folin reagent. Results of this work showed that all fungal isolates were able to grow on Zibar. However, only one isolate showed significant reduction of total phenols. The concentration of phenols in the presence of isolate OMWW2 was 57.75 mg/ml compared to 159.27 mg/ml in the control untreated water. In addition to obtain percernt of germination approximatly 83% in 100% T Zibar, with no significant differences in germination percent compared with water-soaked seeds as control. While the germination percent in untreated Zibar was 0%. This isolate was identified by sequencing as Paecilomyces sp., F-BTUL-E1 isolate, in Eurotiomycetes class of fungi.