Abstract
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.