Bacterial Biotransformation of Oleic Acid: New Findings on the Formation of γ-Dodecalactone and 10-Ketostearic Acid in the Culture of Micrococcus luteus

Abstract

<jats:p>Microbial conversion of oleic acid (1) to form value-added industrial products has gained increasing scientific and economic interest. So far, the production of natural lactones with flavor and fragrance properties from fatty acids by non-genetically modified organisms (non-GMO) involves whole cells of bacteria catalyzing the hydration of unsaturated fatty acids as well as yeast strains responsible for further β-oxidation processes. Development of a non-GMO process, involving a sole strain possessing both enzymatic activities, significantly lowers the costs of the process and constitutes a better method from the customers’ point of view regarding biosafety issues. Twenty bacteria from the genus of Bacillus, Comamonas, Dietzia, Gordonia, Micrococcus, Pseudomonas, Rhodococcus and Streptomyces were screened for oxidative functionalization of oleic acid (1). Micrococcus luteus PCM525 was selected as the sole strain catalyzing the one-pot transformation of oleic acid (1) into natural valuable peach and strawberry-flavored γ-dodecalactone (6) used in the food, beverage, cosmetics and pharmaceutical industries. Based on the identified products formed during the process of biotransformation, we clearly established a pathway showing that oleic acid (1) is hydrated to 10-hydroxystearic acid (2), then oxidized to 10-ketostearic acid (3), giving 4-ketolauric acid (4) after three cycles of β-oxidation, which is subsequently reduced and cyclized to γ-dodecalactone (6) (Scheme 1). Moreover, three other strains (Rhodococcus erythropolis DSM44534, Rhodococcus ruber PCM2166, Dietzia sp. DSM44016), with high concomitant activities of oleate hydratase and alcohol dehydrogenase, were identified as efficient producers of 10-ketostearic acid (3), which can be used in lubricant and detergent formulations. Considering the prevalence of γ-dodecalactone (6) and 10-ketostearic acid (3) applications and the economic benefits of sustainable management, microbial bioconversion of oleic acid (1) is an undeniably attractive approach.</jats:p>

Stereoselective synthesis of whisky lactone isomers catalyzed by bacteria in the genus Rhodococcus

“…By comparing the results from the submerged preparative biotransformations described herein with our previous results obtained by solid-state fermentation (Boratyński et al, 2020), processes conducted in the SmF were characterized by the substantially greater and faster conversion of diols to corresponding whisky lactones. Moreover, the bio-oxidation carried out in SmF afforded enantiomerically pure lactones on a preparative scale, which could not be obtained in preparative SSF biotransformations.…”

“…Initial biotransformations were carried out in MTPs. This allowed us a rapid selection of microorganisms with high ADH activity, responsible for the stereoselective oxidation of racemic diols to corresponding chiral lactones (Boratyński et al, 2013(Boratyński et al, , 2016(Boratyński et al, , 2020.…”

Oxidation of threo‐9,10‐Dihydroxystearic Acid Mediated by Micrococcus luteus as a Key Step in the Conversion of Oleic Acid into Pelargonic and Azelaic Acids

“…Nevertheless, in the screening biotransformations with Streptomyces griseus DSM40395 and Micrococcus luteus PCM525, the formation of a mixture of the two regioisomeric hydroxyketones 5 a and 5 b was observed with a conversion of 30 and 40 %, respectively, as shown by GC/MS analysis. M. luteus PCM525 was selected for further studies, also on the basis of our recently published results, showing the high ADH activity of the microorganism in the transformation of 10‐hydroxystearic acid into 10‐oxostearic acid [8] . When the oxidation of diol 1 with the growing cells of M. luteus PCM525 was performed on preparative scale (50 g/L of substrate 1 dissolved in EtOH) in TSB medium, derivatives 5 were obtained in maximum 30 % conversion (estimated by 1 H NMR analysis as the molar ratio between compounds 5 and starting diol 1 ) after three days.…”

“…M. luteus PCM525 was selected for further studies, also on the basis of our recently published results, showing the high ADH activity of the microorganism in the transformation of 10-hydroxystearic acid into 10-oxostearic acid. [8] When the oxidation of diol 1 with the growing cells of M. luteus PCM525 was performed on preparative scale (50 g/L of substrate 1 dissolved in EtOH) in TSB medium, derivatives 5 were obtained in maximum 30 % conversion (estimated by 1 H NMR analysis as the molar ratio between compounds 5 and starting diol 1) after three days. Based on the literature, the optimum pH for oxidation reactions catalyzed by commercial alcohol dehydrogenases is in the range 8.5-9.0, therefore the reaction with resting cells of M. luteus PCM525 was further investigated in this pH range.…”

Biotechnological formation of dairy flavor inducing δ-lactones from vegetable oil

“…In the light of this information, it is justified to evaluate the effect of a pre-fermentation step (an additional fermentation step that allows the bacteria to adapt to the new media) and the growth phase in which bacteria is harvested on lactone formation. A study by Boratyński, Szczepańska, De Simeis, Serra, and Brenna (2020 ), did investigate the effect of the growth phase and found the stationary phase to be favorable for γ-dodecalactone formation by Micrococcus luteus . However, due to limited literature available on this matter, it is not established if this is a general trend, is species specific, and/or whether this holds for lactones other than γ-dodecalactone.…”