PMCC PMCC

Search tips
Search criteria

Advanced
Results 26-50 (264)
 

Clipboard (0)
None

Select a Filter Below

Journals
Year of Publication
Document Types
26.  Highly conserved salt bridge stabilizes a proteinase K subfamily enzyme, Aqualysin I, from Thermus aquaticus YT-1 
AMB Express  2014;4:59.
The proteinase K subfamily enzymes, thermophilic Aqualysin I (AQN) from Thermus aquaticus YT-1 and psychrophilic serine protease (VPR) from Vibrio sp. PA-44, have six and seven salt bridges, respectively. To understand the possible significance of salt bridges in the thermal stability of AQN, we prepared mutant proteins in which amino acid residues participating in salt bridges common to proteinase K subfamily members and intrinsic to AQN were replaced to disrupt the bridges one at a time. Disruption of a salt bridge common to proteinase K subfamily enzymes in the D183N mutant resulted in a significant reduction in thermal stability, and a massive change in the content of the secondary structure was observed, even at 70°C, in the circular dichroism (CD) analysis. These results indicate that the common salt bridge Asp183-Arg12 is important in maintaining the conformation of proteinase K subfamily enzymes and suggest the importance of proximity between the regions around Asp183 and the N-terminal region around Arg12. Of the three mutants that lack an AQN intrinsic salt bridge, D212N was more prone to unfolding at 80°C than the wild-type enzyme. Similarly, D17N and E237Q were less thermostable than the wild-type enzyme, although this may be partially due to increased autolysis. The AQN intrinsic salt bridges appear to confer additional thermal stability to this enzyme. These findings will further our understanding of the factors involved in stabilizing protein structure.
doi:10.1186/s13568-014-0059-2
PMCID: PMC4131155  PMID: 25136511
Serine protease; Subtilase; Proteinase K subfamily; Salt bridge; Thermal stability
27.  Production of therapeutic proteins in the chloroplast of Chlamydomonas reinhardtii 
AMB Express  2014;4:57.
Chloroplast transformation in the photosynthetic alga Chlamydomonas reinhardtii has been used to explore the potential to use it as an inexpensive and easily scalable system for the production of therapeutic recombinant proteins. Diverse proteins, such as bacterial and viral antigens, antibodies and, immunotoxins have been successfully expressed in the chloroplast using endogenous and chimeric promoter sequences. In some cases, proteins have accumulated to high level, demonstrating that this technology could compete with current production platforms. This review focuses on the works that have engineered the chloroplast of C. reinhardtii with the aim of producing recombinant proteins intended for therapeutical use in humans or animals.
doi:10.1186/s13568-014-0057-4
PMCID: PMC4131161  PMID: 25136510
Chlamydomonas; Chloroplast transformation; Recombinant therapeutic proteins
28.  Cultivation and detection of endophytic aerobic methanotrophs isolated from Sphagnum species as a perspective for environmental biotechnology 
AMB Express  2014;4:58.
Enriched cultures of microorganisms are an essential step in the production of inoculum of these organisms for biotechnology and bioengineering. The potential application of methanotrophic microorganisms for removal of methane produced from landfills and coal mines as well as biodegradation of toxic compounds has been widely studied. Therefore, searching for new sources of methanotrophs can contribute to increasing the possibilities of biotechnology and bioengineering.
Enrichment cultures of endophytic methanotrophs from Sphagnum sp. were initiated in NMS medium, a most widely used medium for cultivation of methanotrophic bacteria from various environments proposed in 1970 by Whittenbury. Incubation was carried out at 10, 20, 30, and 37°C with vigorous shaking on a shaker (180 rpm). The source of carbon and energy for endophytes were methane at the concentration range between 1-20%.
It appeared that the consortium of endophytic bacteria grew only at the temperature of 20 and 30°C. During the culture of endophytes, the measurements of gas concentration showed a steady loss of methane and oxygen, as well as accumulation of carbon dioxide as a CH4 oxidation product.
The use of FISH has made characterization of endophytic consortia possible. It turned out that the population of endophytes consists of type I and II methanotrophs as well as associated non-methanotrophic bacteria.
Furthermore, we determined the potential of the examined bacteria for methane oxidation, which ranged up to 4,7 μMCH4 per ml of the population of endophytes per day.
doi:10.1186/s13568-014-0058-3
PMCID: PMC4230809  PMID: 25401064
Endophytic bacteria; Methanotrophs; Methane; Sphagum sp
29.  Re-assessment of YAP1 and MCR1 contributions to inhibitor tolerance in robust engineered Saccharomyces cerevisiae fermenting undetoxified lignocellulosic hydrolysate 
AMB Express  2014;4:56.
Development of robust yeast strains that can efficiently ferment lignocellulose-based feedstocks is one of the requirements for achieving economically feasible bioethanol production processes. With this goal, several genes have been identified as promising candidates to confer improved tolerance to S. cerevisiae. In most of the cases, however, the evaluation of the genetic modification was performed only in laboratory strains, that is, in strains that are known to be quite sensitive to various types of stresses. In the present study, we evaluated the effects of overexpressing genes encoding the transcription factor (YAP1) and the mitochondrial NADH-cytochrome b5 reductase (MCR1), either alone or in combination, in an already robust and xylose-consuming industrial strain of S. cerevisiae and evaluated the effect during the fermentation of undiluted and undetoxified spruce hydrolysate. Overexpression of either gene resulted in faster hexose catabolism, but no cumulative effect was observed with the simultaneous overexpression. The improved phenotype of MCR1 overexpression appeared to be related, at least in part, to a faster furaldehyde reduction capacity, indicating that this reductase may have a wider substrate range than previously reported. Unexpectedly a decreased xylose fermentation rate was also observed in YAP1 overexpressing strains and possible reasons behind this phenotype are discussed.
doi:10.1186/s13568-014-0056-5
PMCID: PMC4105880  PMID: 25147754
Saccharomyces cerevisiae; Hydrolysate; Inhibitors; YAP1; MCR1; Ethanol
30.  Common gas phase molecules from fungi affect seed germination and plant health in Arabidopsis thaliana 
AMB Express  2014;4:53.
Fungal volatile organic compounds (VOCs) play important ecophysiological roles in mediating inter-kingdom signaling with arthropods but less is known about their interactions with plants. In this study, Arabidopsis thaliana was used as a model in order to test the physiological effects of 23 common vapor-phase fungal VOCs that included alcohols, aldehydes, ketones, and other chemical classes. After exposure to a shared atmosphere with the 23 individual VOCs for 72 hrs, seeds were assayed for rate of germination and seedling formation; vegetative plants were assayed for fresh weight and chlorophyll concentration. All but five of the VOCs tested (1-decene, 2-n-heptylfuran, nonanal, geosmin and -limonene) had a significant effect in inhibiting either germination, seedling formation or both. Seedling formation was entirely inhibited by exposure to 1-octen-3-one, 2-ethylhexanal, 3-methylbutanal, and butanal. As assayed by a combination of fresh weight and chlorophyll concentration, 2-ethylhexanal had a negative impact on two-week-old vegetative plants. Three other compounds (1-octen-3-ol, 2-ethylhexanal, and 2-heptylfuran) decreased fresh weight alone. Most of the VOCs tested did not change the fresh weight or chlorophyll concentration of vegetative plants. In summary, when tested as single compounds, fungal VOCs affected A. thaliana in positive, negative or neutral ways.
doi:10.1186/s13568-014-0053-8
PMCID: PMC4100562  PMID: 25045602
Volatile organic compound; Arabidopsis thaliana; Fungi; Seed germination; Chlorophyll concentration; Gas chromatography; Mass spectroscopy
31.  Degradative actions of microbial xylanolytic activities on hemicelluloses from rhizome of Arundo donax 
AMB Express  2014;4:55.
Polysaccharidases from extremophiles are remarkable for specific action, resistance to different reaction conditions and other biotechnologically interesting features. In this article the action of crude extracts of thermophilic microorganisms (Thermotoga neapolitana, Geobacillus thermantarcticus and Thermoanaerobacterium thermostercoris) is studied using as substrate hemicellulose from one of the most interesting biomass crops, the giant reed (Arundo donax L.). This biomass can be cultivated without competition and a huge amount of rhizomes remains in the soil at the end of cropping cycle (10–15 years) representing a further source of useful molecules. Optimization of the procedure for preparation of the hemicellulose fraction from rhizomes of Arundo donax, is studied. Polysaccharidases from crude extracts of thermophilic microorganisms revealed to be suitable for total degradative action and/or production of small useful oligosaccharides from hemicelluloses from A. donax. Xylobiose and interesting tetra- and pentasaccharide are obtained by enzymatic action in different conditions. Convenient amount of raw material was processed per mg of crude enzymes. Raw hemicelluloses and pretreated material show antioxidant activity unlike isolated tetra- and pentasaccharide. The body of results suggest that rhizomes represent a useful raw material for the production of valuable industrial products, thus allowing to increase the economic efficiency of A. donax cultivation.
doi:10.1186/s13568-014-0055-6
PMCID: PMC4086442  PMID: 25024928
Biorefinery; Xylan; Thermophilic enzymes; Xylanases; Xylooligosaccharides; Arundo donax
32.  Purification and characterization of a novel lipopeptide from Streptomyces amritsarensis sp. nov. active against methicillin-resistant Staphylococcus aureus 
AMB Express  2014;4:50.
Nowadays antimicrobial lipopeptides are being widely exploited for developing potential therapeutic agents for treating bacterial infections. In the present study, we have purified and characterized an antimicrobial lipopeptide produced by Streptomyces amritsarensis sp. nov. (= MTCC 11845T = JCM 19660T). The lipopeptide was purified using silica gel chromatography, size exclusion chromatography and reverse phase- HPLC. The MS/MS analysis of the lipopeptide revealed that it has amino acid sequence as Ala-Thr-Gly-Ser-His-Gln and a long chain fatty acid tail with six times repeated the molecular mass of 161 Da which is corresponding to -C12H19. Based on the molecular mass (878.5 Da) and amino acid composition, the lipopeptide was identified as a novel lipopeptide. The MIC values of purified lipopeptide against Bacillus subtilis (MTCC 619), Staphylococcus epidermidis (MTCC 435), Mycobacterium smegmatis (MTCC 6) and clinical strain, Methicillin Resistant Staphylococcus aureus (MRSA) were found to be 10, 15, 25 and 45 μg/ml, respectively. It was completely stable at 70°C for 1 h and retained 81.8% activity after autoclaving (121°C for 15 min). It did not show any change in its activity profile between pH 5.0 - 9.0 and is stable to trypsin, proteinase K and lipase enzymes. It was found to be non-mutagenic against Salmonella typhimurium (TA98) and did not show cytotoxicity when checked against Chinese hamster ovary (CHO) cell line. In addition to antibacterial activity it also exhibits biosurfactant activity.
doi:10.1186/s13568-014-0050-y
PMCID: PMC4077001  PMID: 25006539
Antibacterial; Novel; Lipopeptide; Thermostable; Non-toxic
33.  Contamination of water resources by pathogenic bacteria 
AMB Express  2014;4:51.
Water-borne pathogen contamination in water resources and related diseases are a major water quality concern throughout the world. Increasing interest in controlling water-borne pathogens in water resources evidenced by a large number of recent publications clearly attests to the need for studies that synthesize knowledge from multiple fields covering comparative aspects of pathogen contamination, and unify them in a single place in order to present and address the problem as a whole. Providing a broader perceptive of pathogen contamination in freshwater (rivers, lakes, reservoirs, groundwater) and saline water (estuaries and coastal waters) resources, this review paper attempts to develop the first comprehensive single source of existing information on pathogen contamination in multiple types of water resources. In addition, a comprehensive discussion describes the challenges associated with using indicator organisms. Potential impacts of water resources development on pathogen contamination as well as challenges that lie ahead for addressing pathogen contamination are also discussed.
doi:10.1186/s13568-014-0051-x
PMCID: PMC4077002  PMID: 25006540
Pathogens; Contamination; Water resources; Watershed; Pathogens transport
34.  Assessing medium constituents for optimal heterologous production of anhydromevalonolactone in recombinant Aspergillus oryzae 
AMB Express  2014;4:52.
Anhydromevalonolactone (AMVL) is a bioactive natural product that arises from a molecular biology technique using Aspergillus oryzae as a heterologous host. AMVL has been used as a precursor for the synthesis of insect pest control reagents and has numerous applications in the biotechnological and medical industries. In this study, the Plackett-Burman Design and the Central Composite Design, which offer efficient and feasible approaches, were complemented to screen significant parameters and identify the optimal values for maximum AMVL production. The results suggested that sucrose, NaNO3, yeast extract and K2HPO4 were the key factors affecting AMVL production in a complex medium, whereas the major components required for a defined medium were NaNO3, K2HPO4, KH2PO4 and trace elements. These factors were subsequently optimized using the response surface methodology. Under optimal conditions, a maximum AMVL production of 250 mg/L in the complex medium and 200 mg/L in the defined medium was achieved, which represents an increase of approximately 3-4-fold compared to the commonly used malt extract medium.
doi:10.1186/s13568-014-0052-9
PMCID: PMC4077012  PMID: 25006541
Anhydromevalonolactone; Aspergillus oryzae; Plackett-Burman design; Central composite design; Response surface methodology
35.  The effect on growth of Chlamydomonas reinhardtii of flue gas from a power plant based on waste combustion 
AMB Express  2014;4:49.
Flue gases from a power plant based on waste combustion were tested as a carbon dioxide (CO2) source for growing Chlamydomonas reinhardtii. To achieve recognition as an environmentally friendly hydrogen production method, waste gases should be used to grow this hydrogen-producing microalgae. The algae were grown in undiluted flue gas containing 11.4±0.2% CO2 by volume, in diluted flue gas containing 6.7±0.1% or 2.5±0.0% CO2, and in pure liquid CO2 at a concentration of 2.7±0.2%. The NOx concentration was 45±16 mg m-3, the SO2 concentration was 36±19 mg m-3, the HCl concentration 4.1±1.0 mg m-3 and the O2 concentration 7.9±0.2% in the undiluted flue gas. Undiluted flue gas reduced the dry weight production by around 20-25% when grown at a photon flux density (PFD) of 300 μmol m-2 s-1 artificial light and at 24 or 33°C, compared with the other treatments. A less negative effect was found at the highest flue gas concentration when the algae were grown at 75 μmol m-2 s-1 PFD. Growing the algae outdoors at a day length of 12.5 h and a temperature of around 24°C, the dry weight production was higher (about 15%) in the 2.6% CO2 flue gas treatment compared with all other treatments. Reducing the light level by 30% through shading did not affect the dry weight production. Calculated on aerial basis the productivity reached approximately 70 g m-2 day-1 in the 300 μmol m-2 s-1 PFD treatment (corresponding to 25 mol m-2 day-1) and approximately 17 g m-2 day-1 in the 75μmol m-2 s-1 PFD treatment (corresponding to 6.5 mol m-2 day-1). The outdoor production reached around 14 g m-2 day-1. It was concluded that the negative effect of the undiluted flue gas was attributable to the high CO2 concentration and not to the other pollutants.
doi:10.1186/s13568-014-0049-4
PMCID: PMC4230831  PMID: 25401062
Carbon dioxide concentration; Chlamydomonas reinhardtii; Flue gas; Photosynthetic active radiation
36.  Biodegradation of high concentrations of halomethanes by a fermentative enrichment culture 
AMB Express  2014;4:48.
A fermentative enrichment culture (designated DHM-1) that grows on corn syrup was evaluated for its ability to cometabolically biodegrade high concentrations of chloroform (CF), carbon tetrachloride (CT), and trichlorofluoromethane (CFC-11). When provided with corn syrup and vitamin B12 (0.03 mol B12 per mol CF), DHM-1 grew and biodegraded up to 2,000 mg/L of CF in 180 days, with only minor transient accumulation of dichloromethane and chloromethane. CT (15 mg/L) and CFC-11 (25 mg/L) were also biodegraded without significant accumulation of halomethane daughter products. The rate of CF biodegradation followed a Michaelis-Menten-like pattern with respect to the B12 concentration; one-half the maximum rate (66 mg CF/L/d) occurred at 0.005 mol B12 per mol CF. DHM-1 was able to biodegrade 500 mg/L of CF at an inoculum level as low as 10−8 mg protein/L. The highest rate of CF biodegradation occurred at pH 7.7; activity decreased substantially below pH 6.0. DHM-1 biodegraded mixtures of CT, CFC-11, and CF, although CFC-11 inhibited CF biodegradation. Evidence for compete defluorination of CFC-11 was obtained based on a fluoride mass balance. Overall, the results suggest that DHM-1 may be effective for bioaugmentation in source zones contaminated with thousands of milligrams per liter of CF and tens of milligrams per liter of CT and CFC-11.
doi:10.1186/s13568-014-0048-5
PMCID: PMC4230812  PMID: 25401061
Chloroform; Carbon tetrachloride; Trichlorofluoromethane; Vitamin B12; Bioremediation
37.  Printed paper-based arrays as substrates for biofilm formation 
AMB Express  2014;4:32.
The suitability of paper-based arrays for biofilm formation studies by Staphylococcus aureus is demonstrated. Laboratory-coated papers with different physicochemical properties were used as substrates. The array platform was fabricated by patterning the coated papers with vinyl-substituted polydimethylsiloxane (PDMS) -based ink. The affinity of bacteria onto the flexographically printed hydrophobic and smooth PDMS film was very low whereas bacterial adhesion and biofilm formation occurred preferentially on the unprinted areas, i.e. in the reaction arrays. The concentration of the attached bacteria was quantified by determining the viable colony forming unit (CFU/cm2) numbers. The distribution and the extent of surface coverage of the biofilms were determined by atomic force microscopy. In static conditions, the highest bacterial concentration and most highly organized biofilms were observed on substrates with high polarity. On a rough paper surface with low polarity, the biofilm formation was most hindered. Biofilms were effectively removed from a polar substrate upon exposure to (+)-dehydroabietic acid, an anti-biofilm compound.
doi:10.1186/s13568-014-0032-0
PMCID: PMC4077624  PMID: 25006538
Biofilm formation; Staphylococcus aureus; Polarity; Surface roughness; AFM; PDMS
38.  Systematic analysis of the ability of Nitric Oxide donors to dislodge biofilms formed by Salmonella enterica and Escherichia coli O157:H7 
AMB Express  2014;4:42.
Biofilms in the industrial environment could be problematic. Encased in extracellular polymeric substances, pathogens within biofilms are significantly more resistant to chlorine and other disinfectants. Recent studies suggest that compounds capable of manipulating nitric oxide-mediated signaling in bacteria could induce dispersal of sessile bacteria and provide a foundation for novel approaches to controlling biofilms formed by some microorganisms. In this work, we compared the ability of five nitric oxide donors (molsidomine, MAHMA NONOate, diethylamine NONOate, diethylamine NONOate diethylammonium salt, spermine NONOate) to dislodge biofilms formed by non-typhoidal Salmonella enterica and pathogenic E. coli on plastic and stainless steel surfaces at different temperatures. All five nitric oxide donors induced significant (35-80%) dispersal of biofilms, however, the degree of dispersal and the optimal dispersal conditions varied. MAHMA NONOate and molsidomine were strong dispersants of the Salmonella biofilms formed on polystyrene. Importantly, molsidomine induced dispersal of up to 50% of the pre-formed Salmonella biofilm at 4°C, suggesting that it could be effective even under refrigerated conditions. Biofilms formed by E. coli O157:H7 were also significantly dispersed. Nitric oxide donor molecules were highly active within 6 hours of application. To better understand mode of action of these compounds, we identified Salmonella genomic region recA-hydN, deletion of which led to an insensitivity to the nitric oxide donors.
doi:10.1186/s13568-014-0042-y
PMCID: PMC4070026  PMID: 24995149
Biofilm control; Bacterial signaling; Food-borne pathogens; Nitric oxide
39.  Functional characterization and structural modeling of synthetic polyester-degrading hydrolases from Thermomonospora curvata 
AMB Express  2014;4:44.
Thermomonospora curvata is a thermophilic actinomycete phylogenetically related to Thermobifida fusca that produces extracellular hydrolases capable of degrading synthetic polyesters. Analysis of the genome of T. curvata DSM43183 revealed two genes coding for putative polyester hydrolases Tcur1278 and Tcur0390 sharing 61% sequence identity with the T. fusca enzymes. Mature proteins of Tcur1278 and Tcur0390 were cloned and expressed in Escherichia coli TOP10. Tcur1278 and Tcur0390 exhibited an optimal reaction temperature against p-nitrophenyl butyrate at 60°C and 55°C, respectively. The optimal pH for both enzymes was determined at pH 8.5. Tcur1278 retained more than 80% and Tcur0390 less than 10% of their initial activity following incubation for 60 min at 55°C. Tcur0390 showed a higher hydrolytic activity against poly(ε-caprolactone) and polyethylene terephthalate (PET) nanoparticles compared to Tcur1278 at reaction temperatures up to 50°C. At 55°C and 60°C, hydrolytic activity against PET nanoparticles was only detected with Tcur1278. In silico modeling of the polyester hydrolases and docking with a model substrate composed of two repeating units of PET revealed the typical fold of α/β serine hydrolases with an exposed catalytic triad. Molecular dynamics simulations confirmed the superior thermal stability of Tcur1278 considered as the main reason for its higher hydrolytic activity on PET.
doi:10.1186/s13568-014-0044-9
PMCID: PMC4231364  PMID: 25405080
Polyester hydrolase; Synthetic polyester; Polyethylene terephthalate (PET); Thermomonospora curvata
40.  Physiological and growth response of rice plants (Oryza sativa L.) to Trichoderma spp. inoculants 
AMB Express  2014;4:45.
Trichoderma spp., a known beneficial fungus is reported to have several mechanisms to enhance plant growth. In this study, the effectiveness of seven isolates of Trichoderma spp. to promote growth and increase physiological performance in rice was evaluated experimentally using completely randomized design under greenhouse condition. This study indicated that all the Trichoderma spp. isolates tested were able to increase several rice physiological processes which include net photosynthetic rate, stomatal conductance, transpiration, internal CO2 concentration and water use efficiency. These Trichoderma spp. isolates were also able to enhance rice growth components including plant height, leaf number, tiller number, root length and root fresh weight. Among the Trichoderma spp. isolates, Trichoderma sp. SL2 inoculated rice plants exhibited greater net photosynthetic rate (8.66 μmolCO2 m−2 s−1), internal CO2 concentration (336.97 ppm), water use efficiency (1.15 μmoCO2/mmoH2O), plant height (70.47 cm), tiller number (12), root length (22.5 cm) and root fresh weight (15.21 g) compared to the plants treated with other Trichoderma isolates tested. We conclude that beneficial fungi can be used as a potential growth promoting agent in rice cultivation.
doi:10.1186/s13568-014-0045-8
PMCID: PMC4052627  PMID: 24949276
Trichoderma spp; Rice; Physiological response; Growth response
41.  Screening of liquid media and fermentation of an endophytic Beauveria bassiana strain in a bioreactor 
AMB Express  2014;4:47.
A novel approach for biological control of insect pests could be the use of the endophytic entomopathogenic Beauveria bassiana isolate ATP-02. For the utilization of the endophyte as a commercial biocontrol agent, the fungus has to be mass-produced. B. bassiana was raised in shake flask cultures to produce high concentrations of total spores (TS), which include blastospores (BS) and submerged conidiospores (SCS). The highest concentration of 1.33×109 TS/mL and the highest yield of 5.32×1010 TS/g sucrose was obtained in the TKI broth with 5% sugar beet molasses which consists of 50% sucrose as a carbon source. In spite of the lower sugar concentration (2.5%) the amount of TS could be increased up to 11-times in contrast to the cultivation with 5% sucrose. The scale-up to a 2 L stirred tank reactor was carried out at 25°C, 200–600 rpm and 1 vvm at pH 5.5. A TS yield of 5.2×1010 TS/g sucrose corresponding to a SCS yield of 0.2×1010 SCS/g sucrose was obtained after 216 h. With regards to the culture medium the cost of 1012 TS amounts to 0.24 €. Plutella xylostella larvae, which were fed with oilseed rape leaves treated with spores from fermentation resulted in 77 ± 5% mortality. Moreover, spores from submerged cultivation were able to colonize oilseed rape leaves via leaf application. This is the first report of fermentation of an endophytic B. bassiana strain in a low-cost culture medium to very high yields of TS.
doi:10.1186/s13568-014-0047-6
PMCID: PMC4052666  PMID: 24949278
Submerged culture; Fermentation; Beauveria bassiana; Endophyte; Blastospores; Submerged conidiospores; Biological control
42.  The chemical nature of phenolic compounds determines their toxicity and induces distinct physiological responses in Saccharomyces cerevisiae in lignocellulose hydrolysates 
AMB Express  2014;4:46.
We investigated the severity of the inhibitory effects of 13 phenolic compounds usually found in spruce hydrolysates (4-hydroxy-3-methoxycinnamaldehyde, homovanilyl alcohol, vanillin, syringic acid, vanillic acid, gallic acid, dihydroferulic acid, p-coumaric acid, hydroquinone, ferulic acid, homovanillic acid, 4-hydroxybenzoic acid and vanillylidenacetone). The effects of the selected compounds on cell growth, biomass yield and ethanol yield were studied and the toxic concentration threshold was defined for each compound. Using Ethanol Red, the popular industrial strain of Saccharomyces cerevisiae, we found the most toxic compound to be 4-hydroxy-3-methoxycinnamaldehyde which inhibited growth at a concentration of 1.8 mM. We also observed that toxicity did not generally follow a trend based on the aldehyde, acid, ketone or alcohol classification of phenolic compounds, but rather that other structural properties such as additional functional groups attached to the compound may determine its toxicity. Three distinctive growth patterns that effectively clustered all the compounds involved in the screening into three categories. We suggest that the compounds have different cellular targets, and that. We suggest that the compounds have different cellular targets and inhibitory mechanisms in the cells, also compounds who share similar pattern on cell growth may have similar inhibitory effect and mechanisms of inhibition.
doi:10.1186/s13568-014-0046-7
PMCID: PMC4052683  PMID: 24949277
Phenolics; Toxicity; Inhibition; Tolerance; Conversion; Saccharomyces cerevisiae
43.  Erythritol production on wheat straw using Trichoderma reesei 
AMB Express  2014;4:34.
We overexpressed the err1 gene in the Trichoderma reesei wild-type and in the cellulase hyperproducing, carbon catabolite derepressed strain Rut-C30 in order to investigate the possibility of producing erythritol with T. reesei. Two different promoters were used for err1 overexpression in both strains, a constitutive (the native pyruvat kinase (pki) promoter) and an inducible one (the native β-xylosidase (bxl1) promoter). The derived recombinant strains were precharacterized by analysis of err1 transcript formation on D-xylose and xylan. Based on this, one strain of each type was chosen for further investigation for erythritol production in shake flasks and in bioreactor experiments. For the latter, we used wheat straw pretreated by an alkaline organosolve process as lignocellulosic substrate. Shake flask experiments on D-xylose showed increased erythritol formation for both, the wild-type and the Rut-C30 overexpression strain compared to their respective parental strain. Bioreactor cultivations on wheat straw did not increase erythritol formation in the wild-type overexpression strain. However, err1 overexpression in Rut-C30 led to a clearly higher erythritol formation on wheat straw.
doi:10.1186/s13568-014-0034-y
PMCID: PMC4052684  PMID: 24949268
Erythritol; Erythrose reductase; Trichoderma reesei; Wheat straw; Lignocellulose
44.  Integrative gene transfer in the truffle Tuber borchii by Agrobacterium tumefaciens-mediated transformation 
AMB Express  2014;4:43.
Agrobacterium tumefaciens-mediated transformation is a powerful tool for reverse genetics and functional genomic analysis in a wide variety of plants and fungi. Tuber spp. are ecologically important and gastronomically prized fungi (“truffles”) with a cryptic life cycle, a subterranean habitat and a symbiotic, but also facultative saprophytic lifestyle. The genome of a representative member of this group of fungi has recently been sequenced. However, because of their poor genetic tractability, including transformation, truffles have so far eluded in-depth functional genomic investigations. Here we report that A. tumefaciens can infect Tuber borchii mycelia, thereby conveying its transfer DNA with the production of stably integrated transformants. We constructed two new binary plasmids (pABr1 and pABr3) and tested them as improved transformation vectors using the green fluorescent protein as reporter gene and hygromycin phosphotransferase as selection marker. Transformants were stable for at least 12 months of in vitro culture propagation and, as revealed by TAIL- PCR analysis, integration sites appear to be heterogeneous, with a preference for repeat element-containing genome sites.
doi:10.1186/s13568-014-0043-x
PMCID: PMC4052689  PMID: 24949275
Tuber spp; Truffles; Agrobacterium tumefaciens-mediated transformation; T-DNA; binary plasmid; Green fluorescent protein; Hygromycin phosphotransferase; TAIL-PCR
45.  Genome features of Pseudomonas putida LS46, a novel polyhydroxyalkanoate producer and its comparison with other P. putida strains 
AMB Express  2014;4:37.
A novel strain of Pseudomonas putida LS46 was isolated from wastewater on the basis of its ability to synthesize medium chain-length polyhydroxyalkanoates (mcl-PHAs). P.putida LS46 was differentiated from other P.putida strains on the basis of cpn60 (UT). The complete genome of P.putida LS46 was sequenced and annotated. Its chromosome is 5,86,2556 bp in size with GC ratio of 61.69. It is encoding 5316 genes, including 7 rRNA genes and 76 tRNA genes. Nucleotide sequence data of the complete P. putida LS46 genome was compared with nine other P. putida strains (KT2440, F1, BIRD-1, S16, ND6, DOT-T1E, UW4, W619 and GB-1) identified either as biocontrol agents or as bioremediation agents and isolated from different geographical region and different environment. BLASTn analysis of whole genome sequences of the ten P. putida strains revealed nucleotide sequence identities of 86.54 to 97.52%. P.putida genome arrangement was LS46 highly similar to P.putida BIRD1 and P.putida ND6 but was markedly different than P.putida DOT-T1E, P.putida UW4 and P.putida W619. Fatty acid biosynthesis (fab), fatty acid degradation (fad) and PHA synthesis genes were highly conserved among biocontrol and bioremediation P.putida strains. Six genes in pha operon of P. putida LS46 showed >98% homology at gene and proteins level. It appears that polyhydroxyalkanoate (PHA) synthesis is an intrinsic property of P. putida and was not affected by its geographic origin. However, all strains, including P. putida LS46, were different from one another on the basis of house keeping genes, and presence of plasmid, prophages, insertion sequence elements and genomic islands. While P. putida LS46 was not selected for plant growth promotion or bioremediation capacity, its genome also encoded genes for root colonization, pyoverdine synthesis, oxidative stress (present in other soil isolates), degradation of aromatic compounds, heavy metal resistance and nicotinic acid degradation, manganese (Mn II) oxidation. Genes for toluene or naphthalene degradation found in the genomes of P. putida F1, DOT-T1E, and ND6 were absent in the P. putida LS46 genome. Heavy metal resistant genes encoded by the P. putida W619 genome were also not present in the P. putida LS46 genome. Despite the overall similarity among genome of P.putida strains isolated for different applications and from different geographical location a number of differences were observed in genome arrangement, occurrence of transposon, genomic islands and prophage. It appears that P.putida strains had a common ancestor and by acquiring some specific genes by horizontal gene transfer it differed from other related strains.
doi:10.1186/s13568-014-0037-8
PMCID: PMC4230813  PMID: 25401060
Pseudomonas putida; Comparative bioinformatics analysis; Comparative genome analysis; Polyhydroxyalkanoates; Pan-Genome; Insertion sequences; Metabolic diversity
46.  Phenotypic and metabolic traits of commercial Saccharomyces cerevisiae yeasts 
AMB Express  2014;4:39.
Currently, pursuing yeast strains that display both a high potential fitness for alcoholic fermentation and a favorable impact on quality is a major goal in the alcoholic beverage industry. This considerable industrial interest has led to many studies characterizing the phenotypic and metabolic traits of commercial yeast populations. In this study, 20 Saccharomyces cerevisiae strains from different geographical origins exhibited high phenotypic diversity when their response to nine biotechnologically relevant conditions was examined. Next, the fermentation fitness and metabolic traits of eight selected strains with a unique phenotypic profile were evaluated in a high-sugar synthetic medium under two nitrogen regimes. Although the strains exhibited significant differences in nitrogen requirements and utilization rates, a direct relationship between nitrogen consumption, specific growth rate, cell biomass, cell viability, acetic acid and glycerol formation was only observed under high-nitrogen conditions. In contrast, the strains produced more succinic acid under the low-nitrogen regime, and a direct relationship with the final cell biomass was established. Glucose and fructose utilization patterns depended on both yeast strain and nitrogen availability. For low-nitrogen fermentation, three strains did not fully degrade the fructose.
This study validates phenotypic and metabolic diversity among commercial wine yeasts and contributes new findings on the relationship between nitrogen availability, yeast cell growth and sugar utilization. We suggest that measuring nitrogen during the stationary growth phase is important because yeast cells fermentative activity is not exclusively related to population size, as previously assumed, but it is also related to the quantity of nitrogen consumed during this growth phase.
doi:10.1186/s13568-014-0039-6
PMCID: PMC4052691  PMID: 24949272
Yeast; Nitrogen requirements; Stress resistance; Alcoholic fermentation
47.  Identification and characterization of endophytic bacteria from corn (Zea mays L.) roots with biotechnological potential in agriculture 
AMB Express  2014;4:26.
Six endophytic bacteria of corn roots were identified as Bacillus sp. and as Enterobacter sp, by sequencing of the 16S rRNA gene. Four of the strains, CNPSo 2476, CNPSo 2477, CNPSo 2478 and CNPSo 2480 were positive for the nitrogen fixation ability evaluated through the acetylene reduction assay and amplification of nifH gene. Two Bacillus strains (CNPSo 2477 and CNPSo 2478) showed outstanding skills for the production of IAA, siderophores and lytic enzymes, but were not good candidates as growth promoters, because they reduced seed germination. However, the same strains were antagonists against the pathogenic fungi Fusarium verticillioides, Colletotrichum graminicola, Bipolaris maydis and Cercospora zea-maydis. As an indication of favorable bacterial action, Enterobacter sp. CNPSo 2480 and Bacillus sp. CNPSo 2481 increased the root volume by 44% and 39%, respectively, and the seed germination by 47% and 56%, respectively. Therefore, these two strains are good candidates for future testing as biological inoculants for corn.
doi:10.1186/s13568-014-0026-y
PMCID: PMC4052694  PMID: 24949261
Molecular phylogeny; 16S rRNA; nifH; Plant growth promotion; Antagonism
48.  Response surface modeling for hot, humid air decontamination of materials contaminated with Bacillus anthracis ∆Sterne and Bacillus thuringiensis Al Hakam spores 
AMB Express  2014;4:21.
Response surface methodology using a face-centered cube design was used to describe and predict spore inactivation of Bacillus anthracis ∆Sterne and Bacillus thuringiensis Al Hakam spores after exposure of six spore-contaminated materials to hot, humid air. For each strain/material pair, an attempt was made to fit a first or second order model. All three independent predictor variables (temperature, relative humidity, and time) were significant in the models except that time was not significant for B. thuringiensis Al Hakam on nylon. Modeling was unsuccessful for wiring insulation and wet spores because there was complete spore inactivation in the majority of the experimental space. In cases where a predictive equation could be fit, response surface plots with time set to four days were generated. The survival of highly purified Bacillus spores can be predicted for most materials tested when given the settings for temperature, relative humidity, and time. These predictions were cross-checked with spore inactivation measurements.
doi:10.1186/s13568-014-0021-3
PMCID: PMC4052701  PMID: 24949256
Bacillus; Spore; Decontamination; Hot humid air; RSM
49.  Combining the effects of process design and pH for improved xylose conversion in high solid ethanol production from Arundo donax 
AMB Express  2014;4:41.
The impact of pH coupled to process design for the conversion of the energy crop Arundo donax to ethanol was assessed in the present study under industrially relevant solids loadings. Two main process strategies were investigated, i.e. the traditional simultaneous saccharification and co-fermentation (SSCF) and a HYBRID design, where a long high temperature enzymatic hydrolysis step was carried out prior to continued low temperature SSCF, keeping the same total reaction time. Since acetic acid was identified as the major inhibitor in the slurry, the scenarios were investigated under different fermentation pH in order to alleviate the inhibitory effect on, in particular, xylose conversion. The results show that, regardless of fermentation pH, a higher glucan conversion could be achieved with the HYBRID approach compared to SSCF. Furthermore, it was found that increasing the pH from 5.0 to 5.5 for the fermentation phase had a large positive effect on xylose consumption for both process designs, although the SSCF design was more favored. With the high sugar concentrations available at the start of fermentation during the HYBRID design, the ethanol yield was reduced in favor of cell growth and glycerol production. This finding was confirmed in shake flask fermentations where an increase in pH enhanced both glucose and xylose consumption, but also cell growth and cell yield with the overall effect being a reduced ethanol yield. In conclusion this resulted in similar overall ethanol yields at the different pH values for the HYBRID design, despite the improved xylose uptake, whereas a significant increase in overall ethanol yield was found with the SSCF design.
doi:10.1186/s13568-014-0041-z
PMCID: PMC4052779  PMID: 24949274
Bioethanol; High solids loading; Xylose fermentation; SSCF; Enzymatic hydrolysis
50.  Assessment of packed bed bioreactor systems in the production of viral vaccines 
AMB Express  2014;4:25.
Vaccination is believed to be the most effective method for the prevention of infectious diseases. Thus it is imperative to develop cost effective and scalable process for the production of vaccines so as to make them affordable for mass use. In this study, performance of a novel disposable iCELLis fixed bed bioreactor system was investigated for the production of some viral vaccines like Rabies, Hepatitis-A and Chikungunya vaccines in comparison to conventional systems like the commercially available packed bed system and roller bottle system. Vero and MRC-5 cell substrates were evaluated for growth parameters in all the three systems maintaining similar seeding density, multiplicity of infection (MOI) and media components. It was observed that Vero cells showed similar growth in all the three bioreactors whereas MRC-5 cells showed better growth in iCELLis Nano system and roller bottle system. Subsequently, the virus infection and antigen production studies also revealed that for Hepatitis-A and Chikungunya iCELLis Nano bioreactor system was better to the commercial packed bed bioreactor and roller bottle systems. Although for rabies antigen production commercially available packed bed bioreactor system was found to be better. This study shows that different bioreactor platforms may be employed for viral vaccine production and iCELLis Nano is one of such new convenient and a stable platform for production of human viral vaccines.
doi:10.1186/s13568-014-0025-z
PMCID: PMC4052670  PMID: 24949260
Vaccine production; Rabies virus; Chikungunya virus; Hepatitis-A virus; Packed bed bioreactor; iCELLis Nano bioreactor

Results 26-50 (264)