Inhibitive Effect of Eugenol and Its Nanoemulsion on Quorum Sensing-Mediated Virulence Factors and Biofilm Formation by Pseudomonas aeruginosa.

The aim of the present study was to evaluate the quorum sensing (QS) inhibition potential of eugenol and eugenol nanoemulsion against QS-dependent virulence factor production and gene expression, as well as biofilm formation in Pseudomonas aeruginosa. In the current study, eugenol nanoemulsion at a sub-MIC of 0.2 mg/mL specifically inhibited about 50% of the QS-mediated violacein production in Chromobacterium violaceum, as well as the production of N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C12-HSL) and C4-HSL N-acyl homoserine lactone signal molecules, pyocyanin, and swarming motility in P. aeruginosa. The inhibitive effect of eugenol and its nanoemulsion on the expression of the QS synthase genes was concentration dependent, displaying 65 and 52% expression level for lasI, respectively, and 61 and 45% expression level for rhlI, respectively, at a concentration of 0.2 mg/mL. In addition, the inhibitive effect of eugenol and its nanoemulsion on the expression of the rhlA gene responsible for the production of rhamnolipid was also concentration dependent, displaying 65 and 51% expression level for the rhlA gene, respectively, at a concentration of 0.2 mg/mL. Eugenol and its nanoemulsion also displayed 36 and 63% respective inhibition of biofilm formation by P. aeruginosa at the 0.2 mg/mL concentration. Therefore, the nanoemulsion could be used as a novel QS-based antibacterial and antibiofilm agent for the control of harmful bacteria.

Lactulose production by a thermostable glycoside hydrolase from the hyperthermophilic archaeon Caldivirga maquilingensis IC-167.

BACKGROUND: Lactulose has various uses in the food and pharmaceutical fields. Thermostable enzymes have many advantages for industrial exploitation, including high substrate solubilities as well as reduced risk of process contamination. RESULTS: Enzymatic synthesis of lactulose employing a transgalactosylation reaction by a recombinant thermostable glycoside hydrolase (GH1) from the hyperthermophilic archaeon Caldivirga maquilingensis IC-167 was investigated. The optimal pH for lactulose production was found to be 4.5, while the optimal temperature was 85 °C, before it dropped moderately to 83% at 90 °C. However, the relative activity for lactulose synthesis dropped sharply to 35% at 95 °C. At optimal reaction conditions of 70% (w/w) initial sugar substrates with molar ratio of lactose to fructose of 1:4, 15 U mL-1 enzyme concentration and 85 °C, the time course reaction produced a maximum lactulose concentration of 108 g L-1 at 4 h, corresponding to a lactulose yield of 14% and 27 g L-1 h-1 productivity with 84% lactose conversion. The transgalactosylation reaction for lactulose synthesis was greatly influenced by the ratio of galactose donor to acceptor. CONCLUSION: This novel GH1 may be useful for process applications owing to its high activity in very concentrated substrate reaction media and promising thermostability. © 2017 Society of Chemical Industry.

Characterization of a thermostable glycoside hydrolase (CMbg0408) from the hyperthermophilic archaeon Caldivirga maquilingensis IC-167.

BACKGROUND: Hyperthermophilic archaea capable of functioning optimally at very high temperatures are a good source of unique and industrially important thermostable enzymes. RESULTS: A glycoside hydrolase family 1 ß-galactosidase gene (BglB) from a hyperthermophilic archaeon Caldivirga maquilingensis IC-167 was cloned and expressed in Escherichia coli. The recombinant enzyme (CMbg0408) displayed optimum activity at 110 °C and pH 5.0. It also retained 92% and 70% of its maximal activity at 115 and 120 °C, respectively. The enzyme was completely thermostable and active after 120 min of incubation at 80 and 90 °C. It also showed broad substrate specificity with activities of 8876 ± 185 U mg-1 for p-nitrophenyl-ß-d-galactopyranoside, 4464 ± 172 U mg-1 for p-nitrophenyl-ß-d-glucopyranoside, 1486 ± 68 U mg-1 for o-nitrophenyl-ß-d-galactopyranoside, 2250 ± 86 U mg-1 for o-nitrophenyl-ß-d-xylopyranoside and 175 ± 4 U mg-1 for lactose. A catalytic efficiency (kcat /Km ) of 3059 ± 122 mmol L-1 s-1 and Km value of 8.1 ± 0.08 mmol L-1 were displayed towards p-nitrophenyl-ß-d-galactopyranoside. CONCLUSION: As a result of its remarkable thermostability and high activity at high temperatures, this novel ß-galactosidase may be useful for food and pharmaceutical applications. © 2016 Society of Chemical Industry.

Rheological and functional properties of composite sweet potato - wheat dough as affected by transglutaminase and ascorbic acid.

Effect of transglutaminase (TGM) and ascorbic acid (AA) on composite sweet potato - wheat dough functional and rheological properties was studied. Partial substitution of wheat flour with sweet potato flour at the level of 20 % significantly (P ≤ 0.05) reduced glutenin, gliadin, dough stability, protein weakening, storage modulus (G') and viscous modulus (G″). Mixolab revealed that both TGM and AA treated dough had stability and protein weakening closed to wheat dough (control), with TGM treated dough having the highest values. TGM Introduced new cross-link bonds as shown by the change of amino acid concentration, leading to an increase in storage modulus (G') and viscous modulus (G″), with G' being higher at all levels of TGM concentration. The opposite was observed for composite dough treated with AA as measured by controlled - stress rheometer. TGM treatment increased glutenin and gliadin content. Compared with the control, dough treated with AA exhibited high molecular weight of polymers than TGM treated dough. The results indicate that the TGM and AA modification of the mixolab and dynamic rheological characteristics (G' and G″) dependent on the changes of GMP, glutenin, gliadin and protein weakening in the composite dough. TGM and AA treatment could improve functional and rheological properties of sweet potato - wheat dough to levels that might be achieved with normal wheat bread. However, it's extremely important to optimize the concentrations of both additives to obtain the optimum response.

Influence of extraction solvents on antioxidant and antimicrobial activities of the pulp and seed of Anisophyllea laurina R. Br. ex Sabine fruits

Objective: To evaluate the influence of extraction solvents on antioxidant and antimi-crobial activities of the pulp and seed of Anisophyllea laurina R. Br. ex Sabine fruits. Methods: The antibacterial activities of pulp and seed extracts were tested by using disk diffusion method against eight bacterial strains and three fungal strains. Total phenolic, flavonoid, monomeric anthocyanin and tannin contents, and antioxidant activities were determined by spectrometric methods. Results: The antioxidant analysis of pulp extract revealed the strong radical scavenging capacity and total phenolic content (4329.66 mg of gallic acid/100 g), while seed extract showed the high antioxidant activity and total tannin content (5326.78 mg catechin equivalent/100 g). Antibacterial and antifungal activities of methanol and ethanol extracts exhibited potent growth inhibitory activity against Aeromonas hydrophila, Bacillus subtilis, Escherichia coli O157:H7, Pseudomonas aeruginosa, Salmonella Typhimurium and Staphylococcus aureus ATCC 6538 with minimum inhibitory concentration values ranged from 125 to 250 mg/mL. However, seed extract had the strongest potential activity against Aspergillus niger and Candida albicans with minimum inhibitory concentration value of 500 mg/mL compared to pulp extract. Conclusions: Our results therefore demonstratedthatethanoland methanol extractionswere more efficient in extracting antioxidants and bioactive compound in pulp and seed. These results support that these plant extracts can be used for the treatment of bacterial infections.