Brewer's yeast cell wall affects microbiota composition and decreases Bacteroides fragilis populations in an anaerobic gut intestinal model

Brewer's yeast cell wall (BYC) has been reported to have prebiotic activity that improves the microbiotal composition of the human gut. To understand the precise effect of BYC on gut microbiota and its metabolism, we used a three-stage continuous-flow reactor system that mimicked the environment of the large intestine. The reactor system was able to maintain the bacterial community stably for a week. The Bacteroides fragilis population decreased drastically after the addition of BYC into this system while the number of Lactobacillus was stably maintained. In addition, propionate and acetate levels increased drastically. This metabolic change correlated with an increase in a number of specific operational taxonomic units annotated to the genus Veillonella and Megasphaella. These results suggest that BYC affects the composition of microbiota in an in vitro model system.     

Expression of active and inactive recombinant soluble trehalase using baculovirus–silkworm expression system and their glycan structures

Silkworm soluble trehalase was expressed as a fusion protein with an N-terminal or C-terminal hexahistidine tag in a baculovirus–silkworm expression system and assayed for enzymatic activity. Only N-terminally tagged trehalase showed a high activity. This study is the first to report in vitro functional expression of recombinant insect soluble trehalase.     

Methane reforming with CO2 in molten salt using FeO catalyst

Methane dry reforming with CO₂ using FeO powder in molten salt has been investigated at various flow rates of CH₄/CO₂ mixed gases (CH₄/CO₂=1) between 50 and 400 ml/min at 1223 K in an infrared furnace. This work is carried out to determine the usefulness of this method for the chemical storage of solar energy. The CH₄/CO₂ mixed gases passing through the molten salt (Na₂CO₃/K₂CO₃=1) containing the FeO powder were catalytically decomposed into CO, H₂ and H₂O. The product gas mole ratios, CO/H₂/H₂O, were shown to be 3:1:1 for a high flow rate of 200 ml/min and to be CO/H₂=2:1 for a low flow rate of 50 ml/min. The results were explained in terms of the kinetics of the CH₄-reforming reaction and the thermodynamics of the redox process of FeO powder mixed in the molten salt;

CH₄+2FeO2Fe+H₂+CO+H₂O

Fe+CO₂FeO+CO

for a high flow rate, and

FeO+CH₄Fe+2H₂+CO

Fe+CO₂FeO+CO

for a low flow rate.     

Aryl hydrocarbon receptor plays a significant role in mediating airborne particulate-induced carcinogenesis in mice

Urban particulate air pollution is associated with an increased incidence of cancers, and especially lung cancer. Organic extracts of airborne particulate matter (APM) cause cancer in mice, and PAHs adsorbed to APM are associated with particle-induced carcinogenesis. PAHs are agonists for AhR and are predominantly responsible for lung cancer through induction of highly carcinogenic metabolites. PAH metabolization requires CYP1A1 induction through activation of AhR, and therefore we hypothesized that carcinogenesis due to PAHs in APM would be reduced in AhR-/- mice. To examine this hypothesis, we performed a long-term continuous-application study of carcinogenesis in AhR-/- mice using airborne particulate extract (APE) of APM collected in Sapporo. Tumor development (squamous cell carcinoma) occurred in 8 of 17 AhR+/+ mice (47%), but no tumors were found in AhR-/-mice, and CYP1A1 was induced in AhR+/+ mice but not in AhR-/- mice. These results demonstrate that AhR plays a significant role in APE-induced carcinogenesis in AhR+/+ mice and CYP1A1 activation of carcinogenic PAHs is also of importance. Therefore, measurement of CYP1A1 induction in vitro may be useful for assessment of APM-induced carcinogenesis in humans. We also show that PAH-like compounds are major contributors to AhR-mediated carcinogenesis, whereas TCDD and related compounds make a smaller contribution.     

Target validation and ligand development for a pathogenic fungal profilin,using a knock‐down strain of pathogenic yeast Candida glabrata and structure‐based ligand design

The emergence of antifungal drug resistance is triggering vigorous searches for novel antifungal targets and lead compounds. In this study, we focused on fungal profilin, which is a small actin control protein sharing limited homology to human profilin. To validate its potentiality as a target, a profilin‐conditional mutant of the pathogenic yeast Candida glabrata was constructed, using a regulatable Tet promoter, and its growth was monitored in vitro. Repression of profilin expression led to severe growth defect, demonstrating the potential of this protein as a novel antifungal target. Next, novel peptides binding to the active interface of profilin were designed by computer simulation. ELISA analysis showed that these peptides did bind to the wild‐type profilin but bound less strongly to a profilin with amino acid substitutions at the active interface. Hence, we show here that profilin is a potential antifungal target and offer novel peptide ligands. Copyright © 2010 John Wiley & Sons, Ltd.     

Non-destructive Visible/NIR Spectroscopy for Differentiation of Fresh and Frozen-thawed Fish

Nondestructive visible/near‐infrared (NIR) spectroscopy was evaluated to investigate whether fish has been frozen‐thawed. Fresh or frozen‐thawed red sea bream Pagrus major (n= 108) were scanned using a NIRSystems 6500 spectrophotometer equipped with a surface interactance fiber‐optic accessory then discriminated by soft independent modeling of class analogy (SIMCA) and linear discriminant analysis (LDA) based on principal component analysis (PCA) scores. The major effect of freeze‐thawing treatment involves a gross change in total reflectance after freezing and thawing; this arises from changes in light scatter presumably arising from alterations in the physical structure of at least the surface layer of fish. Untreated original absorbance spectra achieved much better (100%) classification accuracy for the prediction samples while the same figures for multiplicative scatter correction (MSC) treated spectra are considerably worse, indicating that scattering is the major information that makes classification work. No incorrect type of classification at all and also there are no samples classified to both groups either. This faster technique has the potential to differentiate fresh and frozen‐thawed fish and could be applied for online or at‐line processing control.     

Hydrogen and ethanol production from glycerol-containing wastes discharged after biodiesel manufacturing process

H2 and ethanol production from glycerol-containing wastes discharged after a manufacturing process for biodiesel fuel (biodiesel wastes) using Enterobacter aerogenes HU-101 was evaluated. The biodiesel wastes should be diluted with a synthetic medium to increase the rate of glycerol utilization and the addition of yeast extract and tryptone to the synthetic medium accelerated the production of H2 and ethanol. The yields of H2 and ethanol decreased with an increase in the concentrations of biodiesel wastes and commercially available glycerol (pure glycerol). Furthermore, the rates of H2 and ethanol production from biodiesel wastes were much lower than those at the same concentration of pure glycerol, partially due to a high salt content in the wastes. In continuous culture with a packed-bed reactor using self-immobilized cells, the maximum rate of H2 production from pure glycerol was 80 mmol/l/h yielding ethanol at 0.8 mol/mol-glycerol, while that from biodiesel wastes was only 30 mmol/l/h. However, using porous ceramics as a support material to fix cells in the reactor, the maximum H2 production rate from biodiesel wastes reached 63 mmol/l/h obtaining an ethanol yield of 0.85 mol/mol-glycerol.     

Prewashing with acidified sodium chlorite reduces pathogenic bacteria in lightly fermented Chinese cabbage

Efficacy of prewashing with acidified sodium chlorite (ASC) for the sanitation of lightly fermented Chinese cabbage was evaluated. The population of the natural microflora on the cabbage leaves was reduced about 2.0 log CFU/g just after washing with ASC, a significant reduction compared with the control distilled water wash (P < or = 0.05). In the control experiment, viable aerobic bacteria increased gradually when incubated at 10 degrees C; however, ASC-washed cabbage maintained a lower microbial concentration. The treatment of Chinese cabbage with ASC reduced the population of artificially inoculated Escherichia coli O157:H7, Salmonella Enteritidis, Staphylococcus aureus, and Listeria monocytogenes by 2.4 log CFU/g. The sanitation efficacy of ASC was 1.6 log CFU/g higher than that of distilled water washing. The viable cell counts of all pathogenic bacteria tested remained constant during 8 days of storage at 10 degrees C for both washing treatments, with the exception of L. monocytogenes, whose viable cell counts increased gradually with time for both treatments. No significant differences in color, odor, taste, and texture in raw leaves were observed after the ASC wash compared with after the distilled water wash. These results indicate that prewashing with ASC could control bacterial growth in lightly fermented Chinese cabbage without changing the product quality.     

Analysis of a 30 kbp plasmid encoding histidine decarboxylase gene in Tetragenococcus halophilus isolated from fish sauce

In order to analyze the genes related to the histamine production, a strain of histamine producing halophilic bacteria, referred to as strain H, was isolated using enrichment culture and dilution-to-extinction methods with histidine broth inoculated from the fish sauce mashes. The two Japanese fish sauce mashes used, accumulate over 1000 mg/l of histamine. Phenotypic and 16 S rRNA gene sequence analyses identified strain H as Tetragenococcus halophilus, the predominant histamine producing bacteria present during fish sauce fermentation. Genetic analyses (PCR and Southern blot) of the histamine producing strain confirmed that the strain harbored a 30 kbp plasmid (pHDC) encoding a single copy of the pyruvoyl dependent histidine decarboxylase gene (hdc). A comparison of hdcA that is a structural gene of histidine decarboxylase among strain H, Lactobacillus hilgardii 0006, L. sakei LTH2076, Oenococcus oeni 9204, T. halophilus and T. muriaticus JCM10006 (T) indicated >99% sequence similarity. The hdc gene cluster consisted of 4 ORFs, hdcP, hdcA, hdcB, and hdcRS, and were almost identical to that of L. hilgardii 0006 with 99% sequence similarity including the structural hdc spacer region. However, the approximately 500 bp regions upstream and downstream of the hdc gene were different between that of strain H and L. hilgardii 0006. The complete sequence of pHDC revealed 29,924 nucleotides including 28 ORFs, two pairs of IR (inverted repeat), similar sequence of plasmid conjugative elements, and a theta-type replicon. These results suggested that hdc could be encoded on transformable elements among lactic acid bacteria.     

Effects of sources of carbon and nitrogen on production of α-glucosidase inhibitor by a newly isolated strain of Bacillus subtilis B2

This study examined production of α-glucosidase inhibitors by Bacillus subtilis B2 in Luria-Bertani (LB) fermentation with okara, soy powder, starch or pectin as additional source of carbon and nitrogen. All the fermentation broths of B. subtilis B2 exhibited gradual increase in α-glucosidase inhibitory activity during the fermentation process with or without supplemented source of carbon or nitrogen. Addition of okara into the LB medium greatly enhanced the strength (nearly twice as much of that without okara supplement) of α-glucosidase inhibitory activity of fermentation broth. The α-glucosidase inhibitory activity of B. subtilis B2 fermentation broth was positively correlated (p < 0.05) with the bacterial populations grown in LB medium containing okara. Glucose and sucrose were not detected in LB medium during the entire fermentation process and were both reduced drastically in media containing okara, soy powder, starch or pectin after 6 days of fermentation. The fermented LB medium containing okara by B. subtilis B2 possessed very strong α-glucosidase inhibitory activity and contained little glucose and sucrose, suggesting that fermentation of B. subtilis B2 in LB added with okara might be considered as a strategy for preparing functional foods for diabetic patients.