BackgroundStyrene and its derivatives as monomers and petroleum-based feedstocks are valuable as raw materials in industrial processes. The chemical reaction for styrene production uses harsh reaction conditions such as high temperatures or pressures, or requires base catalysis with microwave heating. On the other hand, production of styrene and its derivatives in Escherichia coli is an environmental friendly process to produce conventional petroleum-based feedstocks.ResultsAn artificial biosynthetic pathway was developed in E. coli that yields 4-hydroxystyrene, 3,4-dihydroxystyrene and 4-hydroxy-3-methoxystyrene from simple carbon sources. This artificial biosynthetic pathway has a codon-optimized phenolic acid decarboxylase (pad) gene from Bacillus and some of the phenolic acid biosynthetic genes. E. coli strains with the tal and pad genes, the tal, sam5, and pad genes, and the tal, sam5, com, and pad genes produced 4-hydroxystyrene, 3,4-dihydroxystyrene and 4-hydorxy-3-methoxystyrene, respectively. Furthermore, these pathways were expressed in a tyrosine overproducing E. coli. The yields for 4-hydroxystyrene, 3,4-dihydroxystyrene and 4-hydorxy-3-methoxystyrene reached 355, 63, and 64 mg/L, respectively, in shaking flasks after 36 h of cultivation.ConclusionsOur system is the first to use E. coli with artificial biosynthetic pathways for the de novo synthesis of 3,4-dihydroxystyrene and 4-hydroxy-3-methoxystyrene in a simple glucose medium. Similar approaches using microbial synthesis from simple sugar could be useful in the synthesis of plant-based aromatic chemicals.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-015-0268-7) contains supplementary material, which is available to authorized users.

BackgroundMethylated resveratrol analogs show similar biological activities that are comparable with those of the resveratrol. However, the methylated resveratrol analogs exhibit better bioavailability as they are more easily transported into the cell and more resistant to degradation. Although these compounds are widely used in human health care and in industrial materials, at present they are mainly obtained by extraction from raw plant sources. Accordingly their production can suffer from a variety of economic problems, including low levels of productivity and/or heterogeneous quality. On this backdrop, large-scale production of plant metabolites via microbial approaches is a promising alternative to chemical synthesis and extraction from plant sources.ResultsAn Escherichia coli system containing an artificial biosynthetic pathway that produces methylated resveratrol analogues, such as pinostilbene (3,4’-dihydroxy-5-methoxystilbene), 3,5-dihydroxy-4’-methoxystilbene, 3,4’-dimethoxy-5-hydroxystilbene, and 3,5,4’-trimethoxystilbene, from simple carbon sources is developed. These artificial biosynthetic pathways contain a series of codon-optimized O-methyltransferase genes from sorghum in addition to the resveratrol biosynthetic genes. The E. coli cells that harbor pET-opTLO1S or pET-opTLO3S produce the one-methyl resveratrol analogues of 3,5-dihydroxy-4’-methoxystilbene and pinostilbene, respectively. Furthermore, the E. coli cells that harbor pET-opTLO13S produce 3,5-dihydroxy-4’-methoxystilbene, bis-methyl resveratrol (3,4’-dimethoxy-5-hydroxystilbene), and tri-methyl resveratrol (3,5,4’-trimethoxystilbene).ConclusionsOur strategy demonstrates the first harness microorganisms for de novo synthesis of methylated resveratrol analogs used a single vector system joined with resveratrol biosynthetic genes and sorghum two resveratrol O-methyltransferase genes. Thus, this is also the first report on the production of the methylated resveratrol compounds bis-methyl and tri-methyl resveratrol (3,4’-dimethoxy-5-hydroxystilbene and 3,5,4’-trimethoxystilbene) in the E. coli culture. Thus, the production of the methylated resveratrol compounds was performed on the simple E. coli medium without precursor feeding in the culture.

We studied seed macro- and micro-morphological characteristics of 48 Allium species (51 accessions) belonging to 24 sections and 7 subgenera. Our taxonomic sampling focused on the central Asian regions of Uzbekistan, Kyrgyzstan, and Mongolia. The seed length ranged between 1.74 ± 0.16–4.47 ± 0.43 mm and width ranged between 1.06 ± 0.08–3.44 ± 0.23 mm, showing various shapes. The irregular and elongated polygonal testa cells occurred in all investigated species. Seed testa sculptures showed high variation in their anticlinal walls associated with different shapes: straight to with U-, S- or Omega-type undulations among the species. The moderately flat to convex periclinal walls with various sized verrucae or granules were found in all investigated taxa. Based on our research, we conclude that seed characteristics such as size, shape, and the seed testa features show their significant variability, revealing key characteristics to support taxonomic relationships and major clades recovered in the molecular phylogeny of the genus Allium. Especially, the anticlinal wall characteristics were highly variable and decisive at the both section and species levels. In addition, widely varied shapes and sizes of the seeds were remarkably effective to distinguish Allium species.