Improvement of green table olive processing wastewater decolorization by Geotrichum candidum

In the current paper, olive processing wastewater (TOPW) decolorization by Geotrichum candidum was investigated. For environmental factor optimization, a 2(3) factorial experimental design was employed, wherein three factors, namely glucose, diammonium tartrate, and pH were varied simultaneously. Then, the interaction between the factors was analyzed using MINITAB 16 statistical software. Glucose and diammonium tartrate and their interactive effect influenced the decolorization yield. Regression models were developed to study the interaction between color removal variables. The effect of various carbon (glucose, glycerol and lactic acid) and nitrogen sources (diammonium tartrate, ammonium sulfate, ammonium nitrate and yeast extract) on the decolorization was further determined. G. candidum showed 63% TOPW decolorization with optimized medium containing glucose (5 g/L) and yeast extract (5 mM nitrogen) at pH 6, with significant reduction of phenolic compounds (60%) and COD (71%). HPLC and FTIR study suggests that decolorization can be attributed to adsorption to biomass and to certain phenolic compound biodegradation. Manganese peroxidase (MnP) and lignin-peroxidase (LiP) are the two enzymes responsible for the TOPW decolorization. With optimized culture conditions, G. candidum had maximum LiP and MnP activities of 58.4 and 78 U/L respectively.