Establishment of culture conditions for bio-transformation of R-(+)-limonene to limonene-1,2-diol by Colletotrichum nymphaeae CBMAI 0864

Structural properties and evaluation of the antiproliferative activity of limonene-1,2-diol obtained by the fungal biotransformation of R-(+)- and S-(-)-limonene

Limonene-1,2-diol is a limonene oxygenated metabolite that possesses eight different stereoisomers, which could result in different biological properties. Nonetheless, the relation between its spatial configuration and biological function is still little explored. The present study aimed to perform the stereoisomers identification using nuclear magnetic resonance (NMR) investigation of the limonene-1,2-diol produced via R-(+)- and S-(-)-limonene biotransformation by Colletotrichum nymphaeae and S-(-)-limonene biotransformation by Fusarium oxysporum 152B. Besides, in vitro antiproliferative activity was evaluated against human tumor and nontumor cell lines. The NMR analysis showed that R-(+)-limonene biotransformation afforded exclusively (+)-(1S,2S,4R-limonene-1,2-diol), whereas S-(-)-limonene biotransformation afforded exclusively (-)-(1R,2R,4S-limonene-1,2-diol) independent on the fungi used. Despite no significant cytostatic effects, a possible influence of stereogenic center on the antiproliferative activity of these limonene biotransformation products was evidenced. Moreover, the lack of in vitro antiproliferative effect of limonene-1,2-diol against nontumor cells suggested a safe dose range for further in vivo evaluations, including food applications.

Screening a Strain of Klebsiella sp. O852 and the Optimization of Fermentation Conditions for Trans-Dihydrocarvone Production

Flavors and fragrances have high commercial value in the food, cosmetic, chemical and pharmaceutical industries. It is interesting to investigate the isolation and characterization of new microorganisms with the ability to produce flavor compounds. In this study, a new strain of Klebsiella sp. O852 (accession number CCTCC M2020509) was isolated from decayed navel orange (Citrus sinensis (L.) Osbeck), which was proved to be capable of converting limonene to trans-dihydrocarvone. Besides, the optimization of various reaction parameters to enhance the trans-dihydrocarvone production in shake flask was performed for Klebsiella sp. O852. The results showed that the yield of trans-dihydrocarvone reached up to 1 058 mg/L when Klebsiella sp. O852 was incubated using LB-M medium for 4 h at 36 °C and 150 rpm, and the biotransformation process was monitored for 36 h after adding 1680 mg/L limonene/ethanol (final ethanol concentration of 0.8% (v/v)). The content of trans-dihydrocarvone increased 16 times after optimization. This study provided a basis and reference for producing trans-dihydrocarvone by biotransformation.

Transformations of Monoterpenes with the p-Menthane Skeleton in the Enzymatic System of Bacteria, Fungi and Insects

The main objective of this article was to present the possibilities of using the enzymatic system of microorganisms and insects to transform small molecules, such as monoterpenes. The most important advantage of this type of reaction is the possibility of obtaining derivatives that are not possible to obtain with standard methods of organic synthesis or are very expensive to obtain. The interest of industrial centers focuses mainly on obtaining particles of high optical purity, which have the desired biological properties. The cost of obtaining such a compound and the elimination of toxic or undesirable chemical waste is important. Enzymatic reactions based on enzymes alone or whole microorganisms enable obtaining products with a specific structure and purity in accordance with the rules of Green Chemistry.

Genomic and Transcriptomic Study for Screening Genes Involved in the Limonene Biotransformation of Penicillium digitatum DSM 62840

α-Terpineol has been widely used in daily chemical, pharmaceutical, food, and flavor industries due to its pleasant odor with high economic value and pharmacological action. Our previous study showed that Penicillium digitatum DSM 62840 was an efficient biocatalyst for the transformation of limonene to α-terpineol. Thus, it was meaningful to explore the genome features and the gene expression differences of strain DSM 62840 during limonene biotransformation, and the detailed bioconversion pathways. In this study, the functional genes related to limonene bioconversion were investigated using genome and transcriptome sequences analysis. The results showed that the P. digitatum DSM 62840 genome was estimated to be 29.09 Mb and it encoded 9,086 protein-encoding genes. The most annotated genes were associated to some protein metabolism and energy metabolism functions. When the threshold for differentially expressed genes (DEGs) was set at twofold ratio, a total of 4,128, and 4,148 DEGs were identified in P_L_12h (limonene-treated condition) compared with P_0h (blank) and P_12h (limonene-untreated blank), respectively. Among them, the expression levels of genes involved in the biosynthesis of secondary metabolites, energy metabolism and ATP-binding cassette (ABC) transporters were significantly altered during the biotransformation. And the reliability of these results was further confirmed by quantitative real-time polymerase chain reaction (RT-qPCR). Moreover, we found that the enzyme participated in limonene biotransformation was inducible. This enzyme was located in the microsome, and it was inhibited by cytochrome P450 inhibitors. This indicated that the cytochrome P450 may be responsible for the limonene bioconversion. Several differentially expressed cytochrome P450 genes were further identified, such as PDIDSM_85260 and PDIDSM_67430, which were significantly up-regulated with limonene treatment. These genes may be responsible for converting limonene to α-terpineol. Totally, the genomic and transcriptomic data could provide valuable information in the discovery of related-genes which was involved in limonene biotransformation, pathogenicity of fungi, and investigation of metabolites and biological pathways of strain DSM 62840.

Optimization of limonene biotransformation for the production of bulk amounts of α-terpineol

The biotransformation of R-(+)-limonene into high concentrations of R-(+)-α-terpineol by Sphingobium sp. was investigated in order to optimize the main process variables (pH, biocatalyst concentration, substrate concentration, temperature and agitation). This strategy comprised the screening of variables by a Plackett-Burman design followed by a Central Composite Design. The statistical analysis showed that the optimal α-terpineol production were at 28 °C and pH 7.0, with a limonene concentration of 350 g/L of organic phase agitation of 200 rpm and a biocatalyst concentration of 2.8 g/L of aqueous phase (OD₆₀₀ = 8). Further trials showed that the R-(+)-α-terpineol concentration was higher (240 g/L after 96 h) when using a ratio of 1:3 (v.v^-1) of organic:aqueous phases. However, the total production and yield (in terms of biomass) of α-terpineol would be maximized for an aqueous:organic ratio of 1:1. The experimental design optimization adopted herein was an effective tool for this type of study.