Treatment of olive mill wastewaters by Yarrowia lipolytica ACA YC 5031, using crude glycerol as a carbon source under sterile/nonsterile conditions and saline environment

Today, more and more bioprocesses are being designed every day due to the high global demand to reuse/recycle/reduce (3R). This research is designed towards the agricultural need to treat olive mill wastewater (OMW) combined with crude glycerol under sterile/nonsterile conditions (to propose a bioprocess less in energy needed) and saline conditions (which can enhance the survival of Yarrowia lipolytica ACA YC 5031. During the experimental execution, microbial fermentation was performed in 250 mL ± 1 mL flasks in olive mill wastewater and water (blank fermentation). The culture conditions were 70.0 g/L crude glycerol (as a carbon source) and 1.0 g/L yeast extract – 1.0 g/L peptone (as a nitrogen source), and the whole cycle of fermentations was performed in 0 % - 7% - 9% salt content, pH=3, and under sterile/nonsterile conditions for 9 days. The results in OMW showed max: biomass – 11.20 g/L at 240 hours - OMW (7% salinity/sterile conditions), fat – 3.67 g/L at 240 hours – OMW (7% salinity/sterile conditions), phenol reduction – 33.10 % at 24 hours – OMW (9%/sterile conditions)/ with 46.67% color reduction, citric acid – 10.20 g/L at 240 hours – OMW (0% salinity/sterile conditions), erythritol – 19.90 g/L at 120 hours – OMW (7% salinity/non sterile conditions), mannitol – 2.50 g/L at 120 hours – OMW (7% salinity/sterile conditions). Overall, the experimental results indicated that both heat treatment and salinity conditions had an impact on the quantitative production of the metabolic products but also on the time that this phenomenon occurred during the fermentation. Promising is the increase in production of erythritol under nonsterile conditions in 7% salinity (compared to 0%), which can be proposed as a non-thermal treatment that requires less energy (meaning it is more economical).