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Objective: To enzymatically synthesize aroma acetoin fatty acid esters, useful as flavor and fragrance ingredients in foods., Results: Immobilized Candida antarctica lipase B (CALB), performed significantly better than lipases from Rhizopus niveus and Candida rugosa in carrying out the esterification of acetoin and fatty acids. C4-C12 straight chain fatty acids were suitable acyl donors and CALB had a strong preference for longer straight chains up to ten carbon atoms. Higher temperatures, 40-60 °C, and higher acetoin/fatty acid molar ratios favored the conversion. The maximum yield of acetoin octanoate obtained was (51 ± 1) % after 24 h reaction time in hexane with 0.25 M octanoic acid, 5:1 excess acetoin and an enzyme concentration of 6 g/mol fatty acid at 60 °C. The enzyme activity declined at a steady rate during reuse at 60 °C and after the 10th cycle, 65 % of initial activity was still be retained., Conclusion: This is the first report of acetoin fatty acid ester synthesis by biological method and CALB has been shown to be effective for the lipase-catalyzed esterification of acetion and C4-C12 straight chain fatty acids.

In the effluents of a biologically treated wastewater from a heavy oil-refining plant, C5-C8 fatty acids including pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, and 2-methylbutanoic acid are often detected. As these residual fatty acids can cause further air and water pollution, a new Myroides isolate ZB35 from activated sludge was explored to degrade these C5-C8 fatty acids in this study. It was found that the biodegradation process involved a lag phase that became prolonged with increasing acyl chain length when the fatty acids were individually fed to this strain. However, when fed as a mixture, the ones with longer acyl chains were found to become more quickly assimilated. The branched 2-methylbutanoic acid was always the last one to be depleted among the five fatty acids under both conditions. Metabolite analysis revealed one possible origin of short chain fatty acids in the biologically treated wastewater. Aroma volatiles including 2-methylbutyl isovalerate, isoamyl 2-methylbutanoate, isoamyl isovalerate, and 2-methylbutyl 2-methylbutanoate were subsequently identified from ZB35 extracts, linking the source of the fruity odor to these esters excreted by Myroides species. To our best knowledge, this is the first finding of these aroma esters in bacteria. From a biotechnological viewpoint, this study has revealed the potential of Myroides species as a promising source of aroma esters attractive for food and fragrance industries.