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1.

Objectives

To evaluate the influence of hydraulic retention time (HRT) and cheese whey (CW) substrate concentration (15 and 25 g lactose l?1) on the performance of EGSB reactors (R15 and R25, respectively) for H2 production.

Results

A decrease in the HRT from 8 to 4 h favored the H2 yield and H2 production rate (HPR) in R15, with maximum values of 0.86 ± 0.11 mmol H2 g COD?1 and 0.23 ± 0.024 l H2 h?1 l?1, respectively. H2 production in R25 was also favored at a HRT of 4 h, with maximum yield and HPR values of 0.64 ± 0.023 mmol H2 g COD?1 and 0.31 ± 0.032 l H2 h?1 l?1, respectively. The main metabolites produced were butyric, acetic and lactic acids.

Conclusions

The EGSB reactor was evaluated as a viable acidogenic step in the two-stage anaerobic treatment of CW for the increase of COD removal efficiency and biomethane production.
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2.
3.
Ruminal acidosis caused by accumulation of lactic acid, a decrease of pH in the rumen and subsequent imbalance of the rumen fermentation process, affects the health and productivity of dairy cows and beef cattle. Direct-fed microbials have potential for use in the control and prevention of ruminal acidosis. This study investigated the interaction between five strains of dairy propionibacteria, Megasphaera elsdenii and Streptococcus bovis in various co-culture combinations in a simulated rumen environment comprising unmodified rumen digesta supplemented with excess glucose. While suppression of lactic acid accumulation by both the dairy propionibacteria and M. elsdenii in the presence of S. bovis in the simulated rumen conditions was evident, propionibacteria were found to be more effective than M. elsdenii in controlling lactic acid levels.  相似文献   

4.
Mechanism and substrate specificity of the proton-coupled amino acid transporter 2 (PAT2, SLC36A2) have been studied so far only in heterologous expression systems such as HeLa cells and Xenopus laevis oocytes. In this study, we describe the identification of the first cell line that expresses PAT2. We cultured 3T3-L1 cells for up to 2 weeks and differentiated the cells into adipocytes in supplemented media containing 2 μM rosiglitazone. During the 14 day differentiation period the uptake of the prototype PAT2 substrate l-[3H]proline increased ~5-fold. The macro- and microscopically apparent differentiation of 3T3-L1 cells coincided with their H+ gradient-stimulated uptake of l-[3H]proline. Uptake was rapid, independent of a Na+ gradient but stimulated by an inwardly directed H+ gradient with maximal uptake occurring at pH 6.0. l-Proline uptake was found to be mediated by a transport system with a Michaelis constant (Kt) of 130 ± 10 μM and a maximal transport velocity of 4.9 ± 0.2 nmol × 5 min?1 mg of protein?1. Glycine, l-alanine, and l-tryptophan strongly inhibited l-proline uptake indicating that these amino acids also interact with the transport system. It is concluded that 3T3-L1 adipocytes express the H+-amino acid cotransport system PAT2.  相似文献   

5.

Objectives

To improve the production of α-ketoglutaric acid (α-KG) from l-glutamate by whole-cell biocatalysis.

Results

A novel and highly active l-glutamate oxidase, SmlGOX, from Streptomyces mobaraensis was overexpressed and purified. The recombinant SmlGOX was approx. 64 kDa by SDS-PAGE. SmlGOX had a maximal activity of 125 ± 2.7 U mg?1 at pH 6.0, 35 oC. The apparent Km and Vmax values of SmlGOX were 9.3 ± 0.5 mM and 159 ± 3 U mg?1, respectively. Subsequently, a co-expression plasmid containing the SmlGOX and KatE genes was constructed to remove H2O2, and the protein levels of SmlGOX were improved by codon optimization. Finally, by optimizing the whole-cell transformation conditions, the production of α-KG reached 77.4 g l?1 with a conversion rate from l-glutamate of 98.5% after 12 h.

Conclusions

An efficient method for the production of α-KG was established in the recombinant Escherichia coli, and it has a potential prospect in industrial application.
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6.

Background

Aerobic granular sludge has become an attractive alternative to the conventional activated sludge due to its high settling velocity, compact structure, and higher tolerance to toxic substances and adverse conditions. Aerobic granular sludge process has been studied intensively in the treatment of municipal and industrial wastewater. However, information on leachate treatment using aerobic granular sludge is very limited.

Methods

This study investigated the treatment performance of old landfill leachate with different levels of ammonium using two aerobic sequencing batch reactors (SBR): an activated sludge SBR (ASBR) and a granular sludge SBR (GSBR). Aerobic granules were successfully developed using old leachate with low ammonium concentration (136 mg L?1 NH4 +-N).

Results

The GSBR obtained a stable chemical oxygen demand (COD) removal of 70% after 15 days of operation; while the ASBR required a start-up of at least 30 days and obtained unstable COD removal varying from 38 to 70%. Ammonium concentration was gradually increased in both reactors. Increasing influent ammonium concentration to 225 mg L?1 N, the GSBR removed 73 ± 8% of COD; while COD removal of the ASBR was 59 ± 9%. The GSBR was also more efficient than the ASBR for nitrogen removal. The granular sludge could adapt to the increasing concentrations of ammonium, achieving 95 ± 7% removal efficiency at a maximum influent concentration of 465 mg L?1 N. Ammonium removal of 96 ± 5% was obtained by the ASBR when it was fed with a maximum of 217 mg L?1 NH4 +-N. However, the ASBR was partially inhibited by free-ammonia and nitrite accumulation rate increased up to 85%. Free-nitrous acid and the low biodegradability of organic carbon were likely the main factors affecting phosphorus removal.

Conclusion

The results from this research suggested that aerobic granular sludge have advantage over activated sludge in leachate treatment.
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7.

Objectives

To investigate the feasibility of coupling carbonyl cyanide m-chlorophenylhydrazone-regulated photohydrogen production by Tetraselmis subcordiformis in a photobioreactor to an alkaline fuel cell (AFC).

Results

H2 evolution kinetics in the AFC integrated process was characterized. The duration of H2 evolution was prolonged and its yield was improved about 1.5-fold (to 78 ± 5 ml l?1) compared with that of the process without AFC. Improved H2 yield was possibly caused by removal of H2 feedback inhibition by H2 consumption in situ. Decreases in the H2 production rate correlated with the gradual deactivation of PSII and hydrogenase activities. The H2 yield was closely associated with catabolism of starch and protein.

Conclusion

A marine green algal CO2-supplemented culture integrated with in situ H2-consumption by an AFC system was developed as a viable protocol for the H2 production.
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8.

Objectives

To enhance succinic acid production in Corynebacterium glutamicum by increasing the supply of NADH and the rate of glucose consumption by decreasing H+-ATPase activity.

Results

A mutant of C. glutamicum NC-3-1 with decreased H+-ATPase activity was constructed. This increased the rate of glycolysis and the supply of NADH. Fermentation of C. glutamicum NC-3-1 gave 39 % higher succinic acid production (113 and 81 g/l), a 29 % higher succinic acid yield (0.94 and 0.73 g succinic acid/g glucose) and decreased by-products formation compared to that of C. glutamicum NC-3 in 5 l bioreactor.

Conclusion

The point mutation in C. glutamicum NC-3-1 increased the rate of glycolysis and resulted in higher succinic acid production, higher succinic acid yield and significantly decreased formation of by-products.
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9.

Aims

The effect of different MeJA doses applied prior to or simultaneously with toxic Al on biochemical and physiological properties of Vaccinium corymbosum cultivars with contrasting Al resistance was studied.

Methods

Legacy (Al-resistant) and Bluegold (Al-sensitive) plants were treated with and without toxic Al under controlled conditions: a) without Al and MeJA, b) 100 μM Al, c) 100 μM Al + 5 μM MeJA, d) 100 μM Al + 10 μM MeJA and e) 100 μM Al + 50 μM MeJA. MeJA was applied to leaves 24 h prior to or simultaneously with Al in nutrient solution. After 48 h, Al-concentration, lipid peroxidation (LP), H2O2, antioxidant activity, total phenols, total flavonoids, phenolic compounds and superoxide dismutase activity (SOD) of plant organs were analyzed.

Results

Al-concentrations increased with Al-treatment in both cultivars, being Al, LP and H2O2 concentrations reduced with low simultaneous MeJA application. Higher MeJA doses induced more oxidative damage than the lowest. Legacy increased mainly non-enzymatic compounds, whereas Bluegold increased SOD activity to counteract Al3+.

Conclusions

Low MeJA doses applied simultaneously with Al3+ increased Al-resistance in Legacy by increasing phenolic compounds, while Bluegold reduced oxidative damage through increment of SOD activity, suggesting a diminution of its Al-sensitivity. Higher MeJA doses could be potentially toxic. Studies are needed to determine the molecular mechanisms involved in the protective MeJA effect against Al-toxicity.
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10.
Megasphaera elsdenii T81 grew on either dl-lactate or d-glucose at similar rates (0.85 h?1) but displayed major differences in the fermentation of these substrates. Lactate was fermented at up to 210-mM concentration to yield acetic, propionic, butyric, and valeric acids. The bacterium was able to grow at much higher concentrations of d-glucose (500 mM), but never removed more than 80 mM of glucose from the medium, and nearly 60 % the glucose removed was sequestered as intracellular glycogen, with low yields of even-carbon acids (acetate, butyrate, caproate). In the presence of both substrates, glucose was not used until lactate was nearly exhausted, even by cells pregrown on glucose. Glucose-grown cultures maintained only low extracellular concentrations of acetate, and addition of exogenous acetate increased yields of butyrate, but not caproate. By contrast, exogenous acetate had little effect on lactate fermentation. At pH 6.6, growth rate was halved by exogenous addition of 60 mM propionate, 69 mM butyrate, 44 mM valerate, or 33 mM caproate; at pH 5.9, these values were reduced to 49, 49, 18, and 22 mM, respectively. The results are consistent with this species’ role as an effective ruminal lactate consumer and suggest that this organism may be useful for industrial production of volatile fatty acids from lactate if product tolerance could be improved. The poor fermentation of glucose and sensitivity to caproate suggests that this strain is not practical for industrial caproate production.  相似文献   

11.

Objectives

To determine the inhibitory activities of flavonoids against NS2B-NS3 protease of ZIKA virus (ZIKV NS2B-NS3pro) expressed in Escherichia coli BL21 (DE3) and their structure activity relationship.

Results

ZIKV NS2B-NS3pro was expressed in E. coli BL21(DE3) as a 35 kDa protein. It had a K m of 26 µM with the fluorogenic peptide Dabcyl-KTSAVLQSGFRKME-Edan. The purified ZIKV NS2B-NS3pro was used for inhibition and kinetic assays to determine the activities of 22 polyphenol compounds. These polyphenol compounds at 100 µM inhibited the activity of ZIKV NS2B-NS3pro by 6.2–88%. Seven polyphenol compounds had IC50 ranging from 22 ± 0.2 to 112 ± 5.5 µM. Myricetin showed a mixed type inhibitory pattern against ZIKV NS2B-NS3pro protease. Its IC50 value was 22 ± 0.2 µM with a K i value of 8.9 ± 1.9 µM.

Conclusion

The chemical structure of a polyphenol compound and its inhibitory activity against ZIKV NS2B-NS3pro can be explored to develop highly selective inhibitors against ZIKV NS2B-NS3pro.
  相似文献   

12.

Objective

To investigate the inhibiting effect of formic acid on acetone/butanol/ethanol (ABE) fermentation and explain the mechanism of the alleviation in the inhibiting effect under CaCO3 supplementation condition.

Results

From the medium containing 50 g sugars l?1 and 0.5 g formic acid l?1, only 0.75 g ABE l?1 was produced when pH was adjusted by KOH and fermentation ended prematurely before the transformation from acidogenesis to solventogenesis. In contrast, 11.4 g ABE l?1 was produced when pH was adjusted by 4 g CaCO3 l?1. The beneficial effect can be ascribed to the buffering capacity of CaCO3. Comparative analysis results showed that the undissociated formic acid concentration and acid production coupled with ATP and NADH was affected by the pH buffering capacity of CaCO3. Four millimole undissociated formic acid was the threshold at which the transformation to solventogenesis occurred.

Conclusion

The inhibiting effect of formic acid on ABE fermentation can be alleviated by CaCO3 supplementation due to its buffering capacity.
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13.

Background

It is well known that dyslipidemia and chronic hyperglycemia increase the onset of diabetes and diabetic complication. The aim of this study is to see the association of trace metals elements and lipid profile among type 2 diabetes mellitus patients.

Methods

The study was conducted on 214 type 2 diabetic patients at Jimma University Specialized Hospital, Jimma, Ethiopia. All the eligible study participants responded to the structured interviewer administered questionnaire and fasting venous blood was drawn for biochemical analysis. Trace metal elements (zinc(Zn+2), magnesium(Mg+2), chromium(Cr+3), calcium(Ca+2), phosphorus(Po4 ?3), manganese(Mn+2), copper(Cu+2), and iron(Fe+3)) and lipid profiles (total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein (HDL-C), and triglycerides (TG)) were measured by atomic absorption spectrophotometry and enzymatic determination method respectively. Data were analyzed by SPSS version 24 software for windows. Bonferroni correction for multiple statistical comparisons was used and a p-value less than 0.01 were accepted as a level of significance.

Result

The mean age of study participants was 42.95(±12.6) with an average of 5.83(±3.1) years being diagnosed with diabetes mellitus. The BMI of female (27.1(±4.9)) was significantly higher than male (25.21(±4.2)). BMI shows positive and significant (p < 0.01) association with lipid profiles (TC, LDL-C, and TG) among type 2 diabetic patients in the liner regression model. In addition, WH-R was positively associated with TG. In Pearson partial correlation adjusted for sex and age, Za+2 shown to have statistically significant and negative correlations with TC, LDL-C and with TG. Mg+2 and Cr+2 negatively and significantly correlated with the lipid profile TC and LDL-C. Ca+2 negatively correlated with TC and TG. Po?3 4 positively correlated with HDL-C; iron negatively correlated with TC. However, in the liner regression model, only calcium positively and significantly (Beta = ?0.21, p < 0.01) associated with TG.

Conclusion

In the current study, a negative correlation was observed between trace metal elements (Zn+2, Mg+2, Cr+3, Ca+2 and Fe+3) and lipid profile (TC, LDL-C and TG) among type 2 diabetes mellitus patients. In addition, Ca+2 observed to be associated with TG. Future studies are highly advised to uncover the bidirectional association between trace metal element and dyslipidemia in diabetic patients.
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14.
The nature of the unusual cation–π interactions between cations (H+, Li+, Na+, Be2+ and Mg2+) and the electron-deficient B=B bond of the triplet state HB=BH ( $ {}^3\Sigma_g^{-} $ ) was investigated using UMP2(full) and UB3LYP methods at 6–311++G(2df,2p) and aug-cc-pVTZ levels, accompanied by a comparison with 1:1 and 2:1 σ-binding complexes between BH and the cations. The binding energies follow the order HB=BH...H+ > HB=BH...Be2+ > HB=BH...Mg2+ ? HB=BH...Li+ > HB=BH...Na+ and HB=BH (1Δg)...M+/M2+ > H2C=CH2...M+/M2+ > HC≡CH...M+/M2+ > HB=BH ( $ {}^3\Sigma_g^{-} $ )...M+/M2+. Furthermore, except for HB...H+, the σ-binding interaction energy of the 1:1 complex HB...M+/M2+ is stronger than the cation–π interaction energy of the C2H2...M+/M2+, C2H4...M+/M2+, B2H2 (1Δg)...M+/M2+ or B2H2 ( $ {}^3\Sigma_g^{-} $ )...M+/M2+ complex, and, for the 2:1 σ-binding complexes, except for HBBe2+...BH, they are less stable than the cation–π complexes of B2H2 (1Δg) or B2H2 ( $ {}^3\Sigma_g^{-} $ ). The atoms in molecules (AIM) theory was also applied to verify covalent interactions in the H+ complexes and confirm that HB=BH ( $ {}^3\Sigma_g^{-} $ ) can be a weaker π-electron donor than HB=BH (1Δg), H2C=CH2 or HC≡CH in the cation–π interaction. Analyses of natural bond orbital (NBO) and electron density shifts revealed that the origin of the cation–π interaction is mainly that many of the lost densities from the π-orbital of B=B and CC multiple bonds are shifted toward the cations.
Figure
The nature of the unusual cation–π interactions between cations (H+, Li+, Na+, Be2+ and Mg2+) and the electron-deficient B=B bond of the triplet state HB=BH ( $ {}^3\Sigma_g^{-} $ ) as investigated using UMP2(full) and UB3LYP methods at 6-311++G(2df,2p) and aug-cc-pVTZ levels  相似文献   

15.

Objectives

To enhance the biosynthesis of medium-chain-length polyhydroxyalkanoates (PHAMCL) from glucose in Pseudomonas mendocina NK-01, metabolic engineering strategies were used to block or enhance related pathways.

Results

Pseudomonas mendocina NK-01 produces PHAMCL from glucose. Besides the alginate oligosaccharide biosynthetic pathway proved by our previous study, UDP-d-glucose and dTDP-l-rhamnose biosynthetic pathways were identified. These might compete for glucose with the PHAMCL biosynthesis. First, the alg operon, galU and rmlC gene were deleted one by one, resulting in NK-U-1(?alg), NK-U-2 (?alg?galU), NK-U-3(alg?galU?rmlC). After fermentation for 36 h, the cell dry weight (CDW) and PHAMCL production of these strains were determined. Compared with NK-U: 1) NK-U-1 produced elevated CDW (from 3.19 ± 0.16 to 3.5 ± 0.11 g/l) and equal PHAMCL (from 0.78 ± 0.06 to 0.79 ± 0.07 g/l); 2) NK-U-2 produced more CDW (from 3.19 ± 0.16 to 3.55 ± 0.23 g/l) and PHAMCL (from 0.78 ± 0.06 to 1.05 ± 0.07 g/l); 3) CDW and PHAMCL dramatically decreased in NK-U-3 (1.53 ± 0.21 and 0.41 ± 0.09 g/l, respectively). Additionally, the phaG gene was overexpressed in strain NK-U-2. Although CDW of NK-U-2/phaG decreased to 1.29 ± 0.2 g/l, PHA titer (%CDW) significantly increased from 24.5 % up to 51.2 %.

Conclusion

The PHAMCL biosynthetic pathway was enhanced by blocking branched metabolic pathways in combination with overexpressing phaG gene.
  相似文献   

16.

Objectives

To optimize the expression of type A ferulic acid esterase (FaeA) from Aspergillus niger in Pichia pastoris X-33 using codon optimization.

Results

Recombinant FaeA was purified from the fermentation broth, with the maximum specific activity of 48.4 ± 0.1 U mg?1. Adding it during mashing process for beer brewing raised the filtration rate by 14.5% while the turbidity and viscosity declined by 22 and 6.9%, respectively. Addition of FaeA increased the concentrations of free ferulic acid (FA) and arabinoxylan (AX) in the wort, while the polymeric arabinoxylans content declined significantly.

Conclusions

Recombinant FaeA was capable to prevent the oxidative gelation of PAX formation by breaking the cross-linking of FA among AX chains and improve the filtration performance of wort.
  相似文献   

17.
Optimization of process parameters for phytase production by Enterobacter sp. ACSS led to a 4.6-fold improvement in submerged fermentation, which was enhanced further in fed-batch fermentation. The purified 62 kDa monomeric phytase was optimally active at pH 2.5 and 60 °C and retained activity over a wide range of temperature (40–80 °C) and pH (2.0–6.0) with a half-life of 11.3 min at 80 °C. The kinetic parameters K m, V max, K cat, and K cat/K m of the pure phytase were 0.21 mM, 131.58 nmol mg?1 s?1, 1.64 × 103 s?1, and 7.81 × 106 M?1 s?1, respectively. The enzyme was fairly stable in the presence of pepsin under physiological conditions. It was stimulated by Ca+2, Mg+2 and Mn+2, but inhibited by Zn+2, Cu+2, Fe+2, Pb+2, Ba+2 and surfactants. The enzyme can be applied in dephytinizing animal feeds, and the baking industry.  相似文献   

18.

Objective

This study was aimed at cloning and characterizing a novel malic enzyme (ME) gene of Mortierella isabellina M6-22 and identifying its relation with lipid accumulation.

Methods

Mime2 was cloned from strain M6-22. Plasmid pET32aMIME2 was constructed to express ME of MIME2 in Escherichia coli BL21. After purification, the optimal pH and temperature of MIME2, as well as Km and Vmax for NADP+ were determined. The effects of EDTA or metal ions (Mn2+, Mg2+, Co2+, Cu2+, Ca2+, or Zn2+) on the enzymatic activity of MIME2 were evaluated. Besides, plasmid pRHMIME2 was created to express MIME2 in Rhodosporidium kratochvilovae YM25235, and its cell lipid content was measured by the acid-heating method. The optimal pH and temperature of MIME2 are 5.8 and 30 °C, respectively.

Results

The act ivity of MIME2 was significantly increased by Mg2+, Ca2+, or Mn2+ at 0.5 mM but inhibited by Cu2+ or Zn2+ (p?<?0.05). The optimal enzymatic activity of MIME2 is 177.46 U/mg, and the Km and Vmax for NADP+ are 0.703 mM and 156.25 μg/min, respectively. Besides, Mime2 transformation significantly increased the cell lipid content in strain YM25235 (3.15?±?0.24 vs. 2.17?±?0.31 g/L, p?<?0.01).

Conclusions

The novel ME gene Mime2 isolated from strain M6-22 contributes to lipid accumulation in strain YM25235.
  相似文献   

19.

Objectives

To find an efficient and cheap system for NAD+ regeneration

Results

A NADH-ferricyanide dehydrogenase was obtained from an isolate of Escherichia coli. Optimal activity of the NADH dehydrogenase was at 45 °C and pH 7.5, with a K m value for NADH of 10 μM. By combining the NADH dehydrogenase, potassium ferricyanide and laccase, a bi-enzyme system for NAD+ regeneration was established. The system is attractive in that the O2 consumed by laccase is from air and the sole byproduct of the reaction is water. During the reaction process, 10 mM NAD+ was transformed from NADH in less than 2 h under the condition of 0.5 U NADH dehydrogenase, 0.5 U laccase, 0.1 mM potassium ferricyanide at pH 5.6, 30 °C

Conclusion

The bi-enzyme system employed the NADH-ferricyanide dehydrogenase and laccase as catalysts, and potassium ferricyanide as redox mediator, is a promising alternative for NAD+ regeneration.
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20.

Objectives

To identify a robust NADP+ dependent formate dehydrogenase from Lactobacillus buchneri NRRL B-30929 (LbFDH) with unique biochemical properties.

Results

A new NADP+ dependent formate dehydrogenase gene (fdh) was cloned from genomic DNA of L. buchneri NRRL B-30929. The recombinant construct was expressed in Escherichia coli BL21(DE3) with 6?×?histidine at the C-terminus and the purified protein obtained as a single band of approx. 44 kDa on SDS-PAGE and 90 kDa on native-PAGE. The LbFDH was highly active at acidic conditions (pH 4.8–6.2). Its optimum temperature was 60 °C and 50 °C with NADP+ and NAD+, respectively and its Tm value was 78 °C. Its activity did not decrease after incubation in a solution containing 20% of DMSO and acetonitrile for 6 h. The KM constants were 49.8, 0.12 and 1.68 mM for formate (with NADP+), NADP+ and NAD+, respectively.

Conclusions

An NADP+ dependent FDH from L. buchneri NRRL B-30929 was cloned, expressed and identified with its unusual characteristics. The LbFDH can be a promising candidate for NADPH regeneration through biocatalysis requiring acidic conditions and high temperatures.
  相似文献   

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