《Table 5–Bacterial identification and indication of lipolytic activity.》

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《Enhanced fat degradation following the addition of a Pseudomonas species to a bioaugmentation product used in grease traps》

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–:no lipase production；++:diameter 0.6–1.1 mm；+++:dimeter1.2–1.7 mm；++++:diameter>1.7 mm.

It was interesting that while the elaidic acid（C18:1n9t）was not detected in the oil at the beginning of the fermentation，it was detected after a few days incubation and it was removed by both the BFL and the BFL-CP1.However，elaidic acid（C18:1n9t）was detected in the accumulated fat of BFL-CP1after the third day of incubation until the end of the run，while the extracellular elaidic acid increased（Table 3）.Similarly to the detection of the elaidic acid after a few days incubation in olive oil，Chipasa and M?drzycka（2008）reported biosynthesis of palmitic acid in the medium，which had not been detected at the beginning.This could occur due to biomodification processes of fatty acids accumulated by the microorganism changing the composition of the substrate fat（Papanikolaou and Aggelis，2011）.Desbois and Smith（2010）reported that free fatty acids with double bonds in the cis orientation tend to have greater antibacterial activity than free fatty acids with double bonds in the trans orientation.Therefore，alterations in the ratio of trans/cis fatty acids of oil by bacteria may be indicative of a protection mechanism against toxicity and account in part for the increase in biomass of BFL observed by day 3.The relative enrichment in stearic acid with both mixed populations that accompanied the removal of elaidic acid as the fermentation progressed to day 13，may also be an indication that BFL is capable of hydrogenation activity，a phenomenon previously described by Papanikolaou and Aggelis（2010）for yeast lipids.It was observed that metabolism of the oleic acid of both fats gave a temporary rise in the levels of stearic acid，as well as of elaidic acid in the study with the olive oil.The accumulated lipids were also consumed.The extracellular oleic acid had the same pattern intracellularly.Fatty acid analysis of the olive oil showed that there was preferential utilization of the unsaturated fatty acids.Mainly in the BFL system unsaturated fatty acids were consumed over their equivalent saturated fatty acids.More specifically，thelongchainunsaturatedfattyacids，palmitoleic acid（C16:1n9c），linoleic acid（C18:2）and cis-11-eicosenoic acid（C20:1）were preferentially used above the saturated fatty acids of the same length，palmitic acid（16:0），stearic acid（18:0）and arachidic acid（20:0），respectively.However，during the fermentation studies of BFL-CP1 on both fats it was observed that the sum of extracellular saturated fatty acids（%）in most cases was higher than 50%indicating the preferential utilization of the unsaturated fatty acids（Tables 3 and 4）.The sum of the accumulated saturated fatty acids（%）was also higher than 50%.Chipasa and M?drzycka（2008）and Novak and Kraus（1973）found that the utilization rate of fatty acids is different and depends on the length and degree of unsaturation of their carbon chains.They found that the maximum utilization rates of 16 and 18carbon saturated fatty acids were lower than those of unsaturated fatty acids with the same chain length.Williams et al.（2012）observed a transformation of FOG fatty acids from unsaturated to saturated forms perhaps due to microbial transformations by bacteria.Moreover，Tang et al.（2012）reported that after the application of Bio-Amp，the unsaturated fatty acids may be transformed to their saturated intermediates before a complete degradation takes place.Additionally，Brooksbank et al.（2007）and Sun and Wakeham（1994）also demonstrated the preferential degradation of unsaturated fatty acids over saturated fatty acids of the same carbon chain length.The results of total fat removal accompanied with the fatty acid analyses showed that BFL had preferential utilization of the unsaturated fatty acids over the saturated fatty acids.In contrast，to the presence of the Pseudomonas species in the BFL-CP1，where a preferential utilization of the unsaturated fatty acids was also observed，however，all the fatty acids were equally consumed.Interestingly，the sum of the accumulated saturated fatty acids（%），which it was higher than 50%，corresponded to a quantity similar to that of the cocoa-butter（Papanikolaou，2011）.That showed a great potential of the new mix population，BFL-CP1，to effectively produce added-value compounds.