Bioscience, Biotechnology, and Biochemistry最新文献

Several extracellular polymeric substances (EPS) produced by bacteria have beneficial applications in the food, pharmaceutical, and cosmetic industries as gelling agents, stabilizers, thickeners, and bioactive ingredients. Most commercialized EPS are derived from soil bacteria, but studies on EPS produced by marine bacteria are scarce. We isolated a marine bacterium Cobetia sp. strain GM, which produces viscous EPS (glycoprotein). Viscosity measurement showed that the EPS of strain GM (GM-EPS) was comparable to commercialized bacterial EPS. Among the tested Cobetia strains, GM-EPS and C. crustatorum EPS were significantly more viscous than other known Cobetia spp. The major constituents of GM-EPS polysaccharide were fucose, glucose, and galactose, which was distinct from exopolysaccharide of known Cobetia spp. This is the first report of a Cobetia sp. strain that produces fucose-rich EPS. GM-EPS protein was rich in hydrophobic and uncharged nonpolar amino acids. GM-EPS exhibited strong emulsion-stabilizing activity that was 1.5 times higher than xanthan.

Propolis is a resinous substance collected by honeybees from the buds and bark of certain trees and plants and is stored in hives. Our previous studies have shown that the major components of propolis from Jeju Island, Korea, are chalcone and coumarin analogs. In this study, we aimed to elucidate the functional properties of propolis obtained from Jeju Island. Propolis extracts from Jeju Island and their main compounds were tested for their tyrosinase inhibitory activity. A 70% ethanol extract of the propolis from Jeju Island and its main component, xanthoangelol (7), showed strong tyrosinase inhibitory activity. Compound 7 showed competitive inhibition against tyrosinase. The predicted structure of the tyrosinase-7 complex showed the same binding sites for 7 and tyrosine, thereby supporting competitive inhibition. Our results indicate that propolis from Jeju Island has the potential to be used as an anti-browning food additive.

Haloalkane dehalogenases (HLDs) convert halogenated compounds to corresponding alcohols by a simple hydrolytic mechanism. Although many bacterial strains possess HLDs or HLD homologues, LinB is the only HLD known to be involved in the utilization of γ-hexachlorocyclohexane (γ-HCH), a man-made chlorinated pesticide. In this study, to gain insight into the functional evolution of HLDs toward the γ-HCH utilization, the linB gene in γ-HCH-degrading Sphingobium japonicum strain UT26 was replaced by 7 other HLD or HLD homologous genes, including 3 putative ancestral enzymes. Interestingly, strains carrying genes for DmmA from marine metagenome or Rluc_anc, an ancestor of Renilla-luciferin 2-monooxygenase (Rluc) and LinB, produced 2,5-dichlorophenol and 2,5-dichlorohydroquinone from γ-HCH, which are indicators of LinB activity, and grew in minimal medium supplied with γ-HCH as a sole carbon source. These results indicated that other HLDs in addition to LinB can play roles in the γ-HCH utilization.

(2E,4S)-3,4,7-Trimethylocta-2,6-dien-1-yl octanoate [(S)-1], decanoate [(S)-2], and dodecanoate [(S)-3] are the main trail pheromone components of the Dufour's gland secretion of the ponerine ant, Holcoponera striatula. We synthesized these pheromone components from an optically active alcohol, (R)-5, by using Johnson-Claisen rearrangement reaction as the key step for constructing a methyl-branched alkyl chain. The alcohol (R)-5 was prepared by using the enzymatic resolution of its racemate. To investigate the biological activity of the enantiomers of these pheromone components, we synthesized the antipodes (R)-1, (R)-2, and (R)-3.

Cinnamic acid (CA) is a widely distributed metabolite in plant species and is a precursor of many important plant molecules such as lignin and flavonoids. CA exists as both trans and cis isomers; the trans isomer is more common in nature. Previous reports have revealed that the cis isomer of CA (cis-CA) has auxin-like activity when exogenously applied. Moreover, cis-CA was found as the endogenous compound in planta. Here, we report the chemical synthesis of stable-isotope-labeled trans- and cis-CA. Using these labeled compounds as internal standards, we developed a quantification method of CA using LC-MS/MS. We identified cis-CA in diverse plant species, including liverwort, moss, and lycophyte implying an important role of cis-CA in the terrestrial plant kingdom.

When brewing microorganisms, which include bacteria and fungi, act on solid cereal substrates, the microbial cell surface interacts with the substrate. When microorganisms use sugars and amino acids released by hydrolysis of the substrate, this occurs on the cell surface. Throughout my career, I have focused on functional studies of cell surface molecules such as solute transporters, cell wall components, and bio-surfactants and applied the knowledge obtained to the development of fermentation technologies. In this review, I describe (i) catabolite control by sugar transporters and energy generation coupled with amino acid decarboxylation in lactic acid bacteria; (ii) recruitment of a polyesterase by the fungal bio-surfactant proteins to polyesters and subsequent promotion of polyester hydrolysis; and (iii) hyphal aggregation via cell wall α-1,3-glucan and galactosaminogalactan in aspergilli and the development of a novel liquid culture method with hyphal dispersed mutants lacking these two polysaccharides.

The cholesterol balance and bile acid metabolism in a mouse model of hepatic lipid accumulation induced by a diet supplemented with cholesterol and cholic acid (CA) were quantitatively evaluated. The mice were fed diets supplemented with different levels of cholesterol (0, 3, or 6 g/kg of diet) and CA (0.5 g/kg of diet) for 6 weeks. Cholesterol supplementation doubled the hepatic triglyceride concentration, regardless of the supplementation level, without inflammation or gallstone formation. Both cholesterol supplementations enhanced fecal excretion of muricholic acid. Additionally, the higher cholesterol supplementation led to an increase in fecal cholesterol excretion, accompanied by elevated expression of hepatic cholesterol exporters and a reduction in fecal bile acid excretion. In this mouse study, supplementation with 3 g cholesterol/kg diet and 0.5 g CA/kg diet was sufficient to induce hepatic lipid accumulation.

Strigolactones (SLs) are allelochemicals attracting both symbiotic arbuscular mycorrhizal (AM) fungi and root parasitic plants and a novel class of phytohormones inhibiting lateral shoot branching. In general, nutrient deficiency significantly promotes SL production in roots and exudation into the rhizosphere, and also induces suppressed shoot branching phenotype in host plants of AM fungi, including rice, tomato, and maize. Nutrient deficiencies also inhibit the shoot branching in Arabidopsis thaliana (hereafter Arabidopsis), a nonhost of AM fungi, while the level of carlactone, a noncanonical SL and the SL precursor for the other SLs, was reported to be unaffected. Because Arabidopsis SLs, including CL and methyl carlactonoate, are highly unstable, relationships between SL levels and shoot branching in Arabidopsis remain elusive. Herein, we demonstrate that nitrogen deficiency increases SL levels in the basal part of shoots in Arabidopsis and lateral shoot branching appears to be strongly regulated by these SLs.

Purple yam (Dioscorea alata L.) is a tuber widely distributed in the tropics and subtropics. We previously isolated several acylated anthocyanins from purple yam. In this study, purple yam extract was orally administered to rats and the absorption of the constituent anthocyanins was investigated. Acylated anthocyanins were detected in the plasma, confirming that they were absorbed into the body as their intact forms. The time required to reach the maximum anthocyanin concentration was 15 min, indicating rapid absorption into the blood. In addition, more than half of the total amount of anthocyanins excreted into the urine was excreted within the first 6 h after administration. To the best of our knowledge, this is the first report of the detection of characteristic acylated anthocyanins from purple yam in rat plasma and urine after oral administration.

The oleaginous yeast Lipomyces starkeyi has a high capacity for starch assimilation, but the genes involved and specific mechanisms in starch degradation remain unclear. This study aimed to identify the critical carbohydrate-active enzyme (CAZyme) genes contributing to starch degradation in L. starkeyi. Comparative transcriptome analysis of cells cultured in glucose and soluble starch medium revealed that 55 CAZymes (including transcript IDs 3772, 1803, and 7314) were highly expressed in soluble starch medium. Protein domain structure and disruption mutant analyses revealed that 3772 encodes the sole secreted α-amylase (LsAmy1p), whereas 1803 and 7314 encode secreted α-glucosidase (LsAgd1p and LsAgd2p, respectively). Triple-gene disruption exhibited severely impaired growth in soluble starch, dextrin, and raw starch media, highlighting their critical role in degrading polysaccharides composed of glucose linked by α-1,4-glucosidic bonds. This study provided insights into the complex starch degradation mechanism in L. starkeyi.