Fats, oils, and greases (FOGs) are a particular environmental threat. Biodegradation of FOGs is a challenge and in this study the biodegradation of waste cooking fats, namely butter and olive oil, was studied using a non‐conventional yeast, Yarrowia lipolytica strain LFMB 20, and a bioaugmentation product consisting of Bacillus spp. and Pseudomonas putida CP1 strain. The microorganisms were grown aerobically in shake‐flask experiments in an enriched medium supplemented with ca 0.85% w/v of waste fat. Analysis of the remaining substrate showed a removal of ca 90% of the fat by the yeast at the end of the incubation, while the bacteria removed ca 95% of both fats. Growth rate, biomass production and biomass yield per unit of fat consumed were all higher for the yeast compared to the bacterial consortium. The bacterial consortium exhibited autolysis and a significant decrease in its DCW value at the late growth phases of both fat substrate cultures. The main fatty acids (FAs) present in both fats were linoleic (Δ9,12C18:2), oleic (Δ9C18:1), palmitic (C16:0), palmitoleic (Δ9C16:1) and stearic (C18:0) acid. Both the bacterial consortium and Y. lipolytica preferentially removed Δ9C18:1 from the medium, while a negative selectivity against C18:0 was reported. Both inocula produced microbial mass that contained intra‐cellular lipid quantities, but the bacterial consortium gave significantly higher lipid in DCW values compared with the yeast (maximum values up to ca 63% w/w for the butter and ca 42% w/w for the olive oil while the respective values for both lipids were 22% ± 2% w/w for Y. lipolytica). In all cases, intra‐cellular lipids in DCW values decreased during the late growth phases, while their FA composition differed with those of the substrate fat.

One of the major environmental problems is the highly toxic agro-industrial waste called olive mill wastewater (OMW), deriving from olive oil production. On the other hand, the continuous development of the biological liquid fuel industry (biodiesel and bioethanol) makes it mandatory the process and exploitation of their main by-products, crude glycerol. This study dealt with the biotechnological conversions of biodiesel-derived crude glycerol with the use of the non-conventional yeast Yarrowia lipolytica in media that had been diluted with OMWs. OMWs, employed as simultaneous liquid medium and substrate, is a new trend recently appearing in Industrial Biotechnology, where value-added metabolites could be produced with simultaneous partial detoxification (i.e. decolorization and phenol removal) of the used residue. In the present study, diluted OMWs (containing 2.0 g/L of total phenolic compounds) blended with 70.0 g/L crude glycerol were employed as substrates. Production of value-added compounds by Y. lipolytica strain ACA-YC 5031 was studied in nitrogen-limited media favoring the production of secondary metabolites (i.e. citric acid, polyols, microbial lipids, polysaccharides). Batch-flask cultures were carried out and the impact of the addition of different NaCl concentrations (1.0%, 3.0%, 5.0% w/w) added upon the biochemical behavior of the strain was studied. Remarkable biomass production was observed in all trials, while in the “blank” experiment (no OMWs and no salt added), the metabolism was shifted toward the synthesis of polyols (Σpolyols = mannitol + arabitol + erythritol > 20 g/L and maximum total citric acid-Cit (sum of citric and isocitric acid) = 10.5 g/L). Addition of OMWs resulted in Citmax = 32.7 g/L, while Σpolyols concentration dropped to <15 g/L. Addition of salt in the OMW-based media slightly reduced the produced biomass, while Cit production drastically increased, reaching a final value of 54.0 g/L (conversion yield of Cit produced per unit of glycerol consumed = 0.82 g/g) in the trial with addition of 5.0% NaCl. Finally, significant color and phenols removal were observed, evaluating the yeast as a decontamination medium for the OMW and a great candidate for the production of value-added compounds.

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A bioaugmentation product, BFL, comprising strains of the genus Bacillus, is evaluated for its ability to degrade fat in laboratory‐scale experiments. Addition of a Pseudomonas putida strain CP1 to the commercial mixed population (BFL‐CP1) is tested for optimization of fat degradation. Experiments are carried out in aerobic batch culture, at 30 °C and 150 rpm for 13 days incubation. A minimal medium (MM) and an enriched nutrient medium (ENM) are investigated supplemented with 1% (w/v) butter. Fat removal is determined gravimetrically and the lipid content is analyzed using thin layer chromatography (TLC) and gas chromatography (GC). No degradation of butter by the product is recorded after 13 days of incubation, while up to 97% degradation is observed by BFL‐CP1. All the Bacillus isolates produced lipase but not the Pseudomonas putida. TLC and GC results suggested that while the Bacillus spp. hydrolyzed the fat to fatty acids and glycerol, complete metabolism of the breakdown products only took place in the presence of the Pseudomonad sp. A citrate buffer is used to investigate fat removal by BFL‐CP1in low and stable pH using citrated minimal buffer. Similar fat removal is observed. The use of citrated minimal buffer caused flocculation of the mixed culture, a phenomenon desirable for fats, oils, and grease (FOGs) degradation in grease traps. Practical Applications: The bioaugmentation product, BFL, comprising strains of the genus Bacillus, only promoted high fat removal in a few days incubation after the addition of a Pseudomonas putida strain CP1. Analysis of the remaining fat suggested a cooperative activity between the Bacillus spp., which hydrolyzed the fat to fatty acids and glycerol, and the Pseudomonas putida CP1, which assimilated the released fatty acids. Formation of flocs were observed when the inoculum was tested under different environmental conditions with low pH. This phenomenon is desirable and along with the high degradative ability of the that new inoculum, it showed good potential for use in the treatment of FOG in grease traps. Fats, oils, and greases (FOGs) are generated in high amounts from food facilities presenting potential blockages and wastewater management problems. FOG may be intercepted at source using grease traps and may be treated biologically in situ using bioaugmentation, an environmentally desirable approach that involves the introduction of suitable microorganisms. In this study, combination of Gram‐positive and Gram‐negative bacteria successfully cooperated and degraded the FOG breaking down the lipids to fatty acids and glycerol by the activity of lipases, and also assimilating the produced fatty acids to carbon dioxide and water through the β‐oxidation process.