Fatma Arous1, Samia Azabou2, Atef Jaouani3, Hela Zouari-Mechichi1, Moncef Nasri1, Tahar Mechichi4. 1. Laboratory of Enzyme Engineering and Microbiology, National School of Engineers of Sfax, University of Sfax, BP 1173, 3038, Sfax, Tunisia. 2. Laboratory of Valorization, Security and Food Analysis, National School of Engineers of Sfax, University of Sfax, Sfax, Tunisia. 3. Laboratoire Microorganismes et Biomolécules Actives, Faculté des Sciences de Tunis, Université Tunis El Manar, Campus Universitaire, 2092, Tunis, Tunisia. 4. Laboratory of Enzyme Engineering and Microbiology, National School of Engineers of Sfax, University of Sfax, BP 1173, 3038, Sfax, Tunisia. tahar.mechichi@enis.rnu.tn.
Abstract
The aim of this study was to assess the potential of newly isolated yeast strains Schwanniomyces etchellsii M2 and Candida pararugosa BM24 to produce yeast biomass on olive mill wastewater (OMW). Maximum biomass yield was obtained at 75% (v/v) OMW, after 96 h of incubation at 30 °C and 5% (v/v) inoculum size. The optimal carbon/nitrogen (C/N) ratio was in the range of 8:1 to 10:1, and ammonium chloride was selected as the most suitable nitrogen source. Under these conditions, a maximum biomass production of 15.11 and 21.68 g L(-1) was achieved for Schwanniomyces etchellsii M2 and Candida pararugosa BM24, respectively. Proteins were the major constituents of yeast cells (35.9-39.4% dry weight), lipids were 2.8-5% dry weight, and ash ranged from 4.8 to 9.5 % dry weight. Besides biomass production, yeast strains were also able to reduce toxicity and polluting parameter levels of the spent OMW-based medium. The practical results presented show that pH rose from initial value of 5.5 to 7.24-7.45 after fermentation. Approximately 23.1-41.4% of the chemical oxygen demand (COD) and 15.4-19.2% of the phenolic compounds were removed. The removal of phenolic compounds was associated with their biodegradation and their partial adsorption on yeast cells.
The aim of this study was to assess the potential of newly isolated yeast strains n class="Species">Schwanniomyces etchellsii M2 and Candida pararugosa BM24 to produce yeast biomass on olive mill wastewater (OMW). Maximum biomass yield was obtained at 75% (v/v) OMW, after 96 h of incubation at 30 °C and 5% (v/v) inoculum size. The optimal carbon/nitrogen (C/N) ratio was in the range of 8:1 to 10:1, and ammonium chloride was selected as the most suitable nitrogen source. Under these conditions, a maximum biomass production of 15.11 and 21.68 g L(-1) was achieved for Schwanniomyces etchellsii M2 and Candida pararugosa BM24, respectively. Proteins were the major constituents of yeast cells (35.9-39.4% dry weight), lipids were 2.8-5% dry weight, and ash ranged from 4.8 to 9.5 % dry weight. Besides biomass production, yeast strains were also able to reduce toxicity and polluting parameter levels of the spent OMW-based medium. The practical results presented show that pH rose from initial value of 5.5 to 7.24-7.45 after fermentation. Approximately 23.1-41.4% of the chemical oxygen demand (COD) and 15.4-19.2% of the phenolic compounds were removed. The removal of phenolic compounds was associated with their biodegradation and their partial adsorption on yeast cells.
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