Production of 8S- and 10S-hydroxy polyunsaturated fatty acids by recombinant Escherichia coli cells expressing mouse arachidonate 8S-lipoxygenase

OBJECTIVE

To quantitatively hydroxylate 8S- and 10S-positions on polyunsaturated fatty acids by recombinant Escherichia coli cells expressing mouse arachidonate 8S-lipoxygenase (8S-LOX).

RESULTS

Hydroxylated products gained from the conversion of arachidonic acid (20:4^{Δ5Z,8Z,11Z,14Z}, AA), eicosapentanoic acid (20:5^{Δ5Z,8Z,11Z,14Z,17Z}, EPA), and (22:6^{Δ4Z,7Z,10Z,13Z,16Z,19Z}, DHA) by recombinant E. coli cells containing 8S-LOX from mouse were identified as 8S-hydroxy-5,9,11,14(Z,E,Z,Z)-eicosatetranoic acid (8S-HETE), 8S-hydroxy-5,9,11,14,17(Z,E,Z,Z,Z)-eicosapentanoic acid (8S-HEPE), and 10S-hydroxy-4,8,12,14,16,19(Z,E,Z,Z,Z,Z)-docosahexaenoic acid (10S-HDoHE), respectively. Under the optimal hydroxylation conditions of pH 7.5, 30 °C, 5% (v/v) ethanol, 15 g cells l^-1, and 5 mM substrate, AA, EPA, and DHA were hydroxylated into 4.37 mM 8S-HETE, 3.77 mM 8S-HEPE, and 3.13 mM 10S-HDoHE for 60, 90, and 60 min, with 87, 75, and 63% molar conversions, respectively.

CONCLUSION

To the best of our knowledge, this is the first quantitatively biotechnological production of 8S-HETE, 8S-HEPE, and 10S-HDoHE.

Molecular characterization of Penicillium oxalicum 6R,8R-linoleate diol synthase with new regiospecificity

Diol synthase-derived metabolites are involved in the sexual and asexual life cycles of fungi. A putative diol synthase from Penicillium oxalicum was found to convert palmitoleic acid (16:1n-7), oleic acid (18:1n-9), linoleic acid (18:2n-6), and α-linolenic acid (18:3n-3) to 6S,8R-dihydroxy-9(Z)-hexadecenoic acid, 6R,8R-dihydroxy-9(Z)-octadecenoic acid, 6R,8R-dihydroxy-9,12(Z,Z)-octadecadienoic acid, and 6S,8R-dihydroxy-9,12,15(Z,Z,Z)-octadecatrienoic acid, respectively, which were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (NMR) spectroscopy analyses. The specific activity and catalytic efficiency of P. oxalicum 6,8-diol synthase were the highest for 18:2n-6, indicating that the enzyme is a 6R,8R-linoleate diol synthase (6R,8R-LDS) with new regiospecificity. This is the first report of a 6R,8R-LDS. LDS is a fusion protein consisting of a dioxygenase domain at the N-terminus and a cytochrome P450/hydroperoxide isomerase (P450/HPI) domain at the C-terminus. The putative active-site residues in the C-terminal domain of P. oxalicum 6R,8R-LDS were proposed based on a substrate-docking homology model. The results of the site-directed mutagenesis within C-terminal P450 domain suggested that Asn⁸⁸⁶, Arg⁷⁰⁷, and Arg⁹³⁴, are catalytic importance and belong to the catalytic groove. Phe⁷⁹⁴ and Gln⁸⁸⁹ were found to be involved in the regiospecific rearrangement of hydroperoxide, while the F794E and Q889A variants of P. oxalicum 6,8-LDS acted as 7,8- and 8,11-LDSs, respectively. All these mutations critically affected the HPI activity of P. oxalicum 6R,8R-LDS.

Complete genome sequence of Stenotrophomonas sp. KACC 91585, an efficient bacterium for unsaturated fatty acid hydration

Hydroxy fatty acids (HFAs) such as 10-hydroxystearic acid (10-HSA) and 10-hydroxy-12(Z)-octadecenoic acid (10-HOD), which are similar to ricinoleic acid, are important starting materials and intermediates for the industrial manufacture of many commodities. Stenotrophomonas sp. KACC 91585, which was isolated from lake sediment, is an efficient bacterium for unsaturated fatty acid hydration that produces 10-HSA and 10-HOD from oleic acid and linoleic acid, respectively, with high conversion rates. The complete genome of this strain is 4,541,729bp with 63.83% GC content and devoid of plasmids. Sets of genes involved in the fatty acid biosynthesis and modification as well as modified lipids were identified in the genome, and these genes were concerned with HFA production. This genome sequence provides molecular information and elucidation for HFA production, and will be used as an efficient biocatalyst source for the biotechnological production of HFA.

Production of 7,8-Dihydroxy Unsaturated Fatty Acids from Plant Oils by Whole Recombinant Cells Expressing 7,8-Linoleate Diol Synthase from Glomerella cingulata

The reaction conditions for the production of 7S,8S-dihydroxy-9,12(Z,Z)-octadecadienoic acid from linoleic acid by recombinant Escherichia coli expressing 7,8-linoleate diol synthase from Glomerella cingulata were optimized using response surface methodology. The optimal reaction conditions were pH 7.0, 18.6 °C, 10.8% (v/v) dimethyl sulfoxide, 44.9 g/L cells, and 14.3 g/L linoleic acid, with agitation at 256 rpm. Under these conditions, recombinant cells produced 7,8-dihydroxy unsaturated fatty acids in the range of 7.0-9.8 g/L from 14.3 g/L linoleic acid, 14.3 g/L oleic acid, and plant oil hydrolysates such as waste oil and olive oil containing 14.3 g/L linoleic acid or oleic acid. To the best of the authors' knowledge, this is the first report on the biotechnological production of 7,8-dihydroxy unsaturated fatty acids.

Production of δ-decalactone from linoleic acid via 13-hydroxy-9(Z)-octadecenoic acid intermediate by one-pot reaction using linoleate 13-hydratase and whole Yarrowia lipolytica cells

OBJECTIVE

To produce δ-decalactone from linoleic acid by one-pot reaction using linoleate 13-hydratase with supplementation with whole Yarrowia lipolytica cells.

RESULTS

Whole Y. lipolytica cells at 25 g l(-1) produced1.9 g l(-1) δ-decalactone from 7.5 g 13-hydroxy-9(Z)-octadecenoic acid l(-1) at pH 7.5 and 30 °C for 21 h. Linoleate 13-hydratase from Lactobacillus acidophilus at 3.5 g l(-1) with supplementation with 25 g Y. lipolytica cells l(-1) in one pot at 3 h produced 1.9 g l(-1) δ-decalactone from 10 g linoleic acid l(-1) via 13-hydroxy-9(Z)-octadecenoic acid intermediate at pH 7.5 and 30°C after 18 h, with a molar conversion yield of 31 % and productivity of 106 mg l(-1) h(-1).

CONCLUSION

To the best of our knowledge, this is the first production of δ-decalactone using unsaturated fatty acid.

Evaluation of bakanae disease progression caused by Fusarium fujikuroi in Oryza sativa L

Bakanae disease caused by Fusarium fujikuroi is an important fungal disease in rice. Among the seven strains isolated from symptomatic rice grains in this study, one strain, FfB14, triggered severe root growth inhibition and decay in the crown and root of rice seedlings. The remaining six strains caused typical Bakanae symptoms such as etiolation and abnormal succulent rice growth. To reveal the relationship between mycelial growth in the infected tissues and Bakanae disease progression, we have established a reliable quantification method using real time PCR that employs a primer pair and dual-labeled probe specific to a unigene encoding F. fujikuroi PNG1 (FfPNG1), which is located upstream of the fumonisin biosynthesis gene cluster. Plotting the crossing point (CP) values from the infected tissue DNAs on a standard curve revealed the active fungal growth of FfB14 in the root and crown of rice seedlings, while the growth rate of FfB20 in rice was more than 4 times lower than FfB14. Massive infective mycelial growth of FfB14 was evident in rice stems and crown; however, FfB20 did not exhibit vigorous growth. Our quantitative evaluation system is applicable for the identification of fungal virulence factors other than gibberellin.

Quantification of rice sheath blight progression caused by Rhizoctonia solani

Rhizoctonia solani has a wide host range, including almost all cultivated crops and its subgroup anastomosis group (AG)-1 IA causes sheath blight in rice. An accurate measurement of pathogen's biomass is a convincing tool for enumeration of this disease. Mycological characteristics and molecular diagnosis simultaneously supported that all six strains in this study were R. solani AG-1 IA. Heterokaryons between strains Rs40104, Rs40105, and Rs45811 were stable and viable, whereas Rs40103 and Rs40106 did not form viable fused cells, except for the combination of Rs40106 and Rs40104. A primer pair was highly specific to RsAROM gene of R. solani strains and the amplified fragment exists as double copies within fungal genome. The relationship between crossing point (CP) values and the amount of fungal DNA was reliable (R (2) >0.99). Based on these results, we determined R. solani's proliferation within infected stems through real time PCR using a primer pair and a Taqman probe specific to the RsAROM gene. The amount of fungal DNA within the 250 ng of tissue DNA from rice cv. Dongjin infected with Rs40104, Rs40105, and Rs45811 were 7.436, 5.830, and 5.085 ng, respectively. In contrast, the fungal DNAs within the stems inoculated with Rs40103 and Rs40106 were 0.091 and 0.842 ng. The sheath blight symptom progression approximately coincided with the amount of fungal DNA within the symptoms. In summary, our quantitative evaluation method provided reliable and objective results reflecting the amount of fungal biomass within the infected tissues and would be useful for evaluation of resistance germplasm or fungicides and estimation of inoculum potential.