Production of Added-Value Chemical Compounds through Bioconversions of Olive-Mill Wastewaters Blended with Crude Glycerol by a Yarrowia lipolytica Strain

Abstract

Olive mill wastewaters (OMW) are the major effluent deriving from olive oil production and are considered as one of the most challenging agro-industrial wastes to treat. Crude glycerol is the main by-product of alcoholic beverage and oleochemical production activities including biodiesel production. The tremendous quantities of glycerol produced worldwide represent a serious environmental challenge. The aim of this study was to assess the ability of Yarrowia lipolytica strain ACA-DC 5029 to grow on nitrogen-limited submerged shake-flask cultures, in crude glycerol and OMW blends as well as in media with high initial glycerol concentration and produce biomass, cellular lipids, citric acid and polyols. The rationale of using such blends was the dilution of concentrated glycerol by OMW to (partially or fully) replace process tap water with a wastewater stream. The strain presented satisfactory growth in blends; citric acid production was not affected by OMW addition (Citmax~37.0 g/L, YCit/Glol~0.55 g/g) and microbial oil accumulation raised proportionally to OMW addition (Lmax~2.0 g/L, YL/X~20% w/w). Partial removal of color (~30%) and phenolic compounds (~10% w/w) of the blended media occurred. In media with high glycerol concentration, a shift towards erythritol production was noted (Erymax~66.0 g/L, YEry/Glol~0.39 g/g) simultaneously with high amounts of produced citric acid (Citmax~79.0 g/L, YCit/Glol~0.46 g/g). Fatty acid analysis of microbial lipids demonstrated that OMW addition in blended media and in excess carbon media with high glycerol concentration favored oleic acid production.

Effect of Salt Addition upon the Production of Metabolic Compounds by Yarrowia lipolytica Cultivated on Biodiesel-Derived Glycerol Diluted with Olive-Mill Wastewaters

“…The increased concentration of OMWs (without prior treatment) in organic matter and phenolic components results in the reduction of the available concentration of oxygen to the organisms. Lack of oxygen to the organisms upsets the balance of ecosystems and the soil porosity, resulting in contaminated aquifers and polluted environments [1,3,4]. Consequent problems are the production of odors, the excessive growth of algae and bacteria, and the appearance of the eutrophication phenomena in aquatic environments in which OMWs are released untreated.…”

“…Value-added metabolites could be produced during these fermentation processes with simultaneous partial detoxification (i.e. decolorization and phenol removal) of the residue [2][3][4][9][10][11].…”

“…lipolytica yeasts are ideal candidates for the remediation and valorization of OMWs as well as of other recalcitrant wastes and residues due to their ability to vigorously grow on a variety of substrates and to tolerate usually hostile growth media [46]. Moreover, Y. lipolytica yeasts have been reported to be capable of producing SCO having equivalent synthesis and value to that of cocoa-butter [47][48][49][50] and a plethora of other value-added compounds during growth on several types of agro-industrial co-products and residues of either fatty or hydrophilic chemical structures [4,36,44,51,52]. The present study investigated the ability of Y. lipolytica strain ACA-YC 5031, a strain that has been reported capable of producing SCO and citric acid during growth on glucose-based media under nitrogen-limited conditions [53], to grow and produce secondary metabolites on mixed nitrogen-limited media consisting of OMWs and biodiesel-derived glycerol.…”

Sustainable Animal Feed Protein through the Cultivation of YARROWIA Lipolytica on Agro-Industrial Wastes and by-Products

“…Most of these studies (e.g., seven) use hydrophobic/oily waste streams [47][48][49][50][51][52][53][54], six refer to crude glycerol [48,51,53,[55][56][57], four to agro-industrial and food waste hydrolysates [58][59][60][61], and three to various agro-industrial waste streams including: mango wastes [62], sugarcane molasses [63], and papaya [54]. Various wild and engineered yeast strains were tested for the production of many different products including: SCP [47,50,53,56], biolipids [47][48][49][50][51][52]59,61], organic acids (mainly citric and succinic) [47,55,56,58,60], and enzymes (mainly lipases) [48,53,54,62]. Although most of the studies are focused on other high-value products apart from SCP, the yeast biomass, after recovery of the main product of interest (e.g., biolipids), would still contain high protein content, rendering it useful as supplement in animal feed.…”

“…Other researchers used hydrophobic AWCB streams to cultivate Yarrowia lipolytica yeast. Sarris et al [47] cultivated ACA-DC 5029 strain in various mixtures of crude glycerol with olive oil mill wastewater. Although crude glycerol (with an initial concentration of 70 g/L) was the main carbon source, olive mill wastewater was used instead of water for dilution of the crude glycerol.…”