Extracting phenolic compounds from microbial biomass after yeast fermentation in olive mill wastewater by organic solvents: a proposal for sustainable waste management and new product development

Olive trees have been cultivated for over 7,000 years in the region of the Mediterranean basin, and they have been an integral part of the culture. The rising consumption of olive oil is also linked to its health benefits, largely due to its phenolic content. For a liter of olive oil produced, 3-5 lt of olive mill wastewater is produced, which is rich in phenolic compounds (1-10 g/L depending on many factors). This work is aiming to approach the initial stages of new product development based on phenolic compounds extracted from microbial biomass after yeast fermentation in olive mill wastewater. During the experiment, 3 microbial yeasts were tested, Yarrowia Lipolytica ACA YC 503, Cryptoccocus curvatus NRRL-15LL, and Rhodosporidium diobovatum EXF-6843, in olive mill wastewater with 3.2 g/L of phenolic compounds (fermentation details to be described). The organic solvents that were used were 100% Ethanol, 70% Ethanol, 100% Ethyl acetate, 70% Ethyl acetate, 100% Methanol, and 70% Methanol, and the microbial mass/organic solvent ratio was 1/18 for 2 hours of contact time at 180 rpm of constant stirring. Three temperature conditions during this contact time were tested: 20 ^oC, 30 ^oC, and 40 ^oC. The results are expressed in RSM charts expressed in both % and g/L extraction. A two-way ANOVA test was performed to identify the influence of the organic solvent, source of microbial mass, and temperature on % extraction in producing valuable data.