Treatment of palm oil mill effluent by thermotolerant polymer-producing fungi

Abstract

Palm oil mill effluent (POME) had acidic pH (pH 4.5) and high C/N ratio that was suitable for fungal treatment. Treatment of POME (15 - 51 g/L) by Humicola insolens D2, Thermomyces lanuginosus E4, and Rhizopus oryzae ST29 for 5 days indicated the optimum concentration of 22.5 g/L soluble COD. R. oryzae ST 29 was most efficient in removal of COD (60.0%), oil & grease (98.6%), and total solids (52.9%). The strain grew well (16.9 g-biomass/L) and also produced the highest biopolymer (26.9 mg/g biomass) with the simultaneous removal of solids from POME. The maximum treatment efficiency and enzyme production (814 U/mL CMCase and 1,550 U/mL xylanase) were achieved after 4 days cultivation. R. oryzae ST 29 was selected for optimization studies which revealed the supplementation of 0.025% fertilizer (46% urea) and the initial pH of 4.5. Under the optimum condition, the treatment increased to 80% COD removal with simultaneous increase of biopolymer by about 2 folds (52.2 mg/g biomass). Therefore, bioaugmentation of R. oryzae ST 29 in POME not only enhanced the treatment efficiency but also generated biomass, enzymes, and biopolymer (MW 17,700 Daltons) as bioproducts.