Selected physiological and biochemical parameters were monitored at the vegetative and reproductive growth stages in potted Bougainvillea plants treated with five different concentrations of TRIA. Advanced flowering, flower bud number, and blooming rate increased significantly with 0.5 and 1.0 mg/L TRIA treatments. Similarly, photosynthetic rate, pigment content, quantum yield, and stomatal conductance increased significantly with 2.5, 1.0, and 5.0 mg/L TRIA treatments. Higher levels of N, P, and K, as well as increased total soluble solids (TSS) and higher sugar and protein contents, were recorded in treated plants. Furthermore, 46% more flowers, a 1.5-fold increase in bract weight, increased longevity, and 40% less leaf abscission were recorded following 2.5 mg/L TRIA treatment. Phenol and flavonoid contents, sucrose phosphate synthase (SPS), and antioxidant activities were also markedly increased with 2.5 and 1.0 mg/L TRIA treatments. However, ethylene production was significantly lower in the treated plants. Positive correlations were observed between leaf TSS and flowering time and flower number, between leaf sugar content and bract weight, and between net photosynthesis and bract growth and dry matter production. It can be concluded that the foliar spray of TRIA stimulates growth, enhances flowering, and improves the quality of potted Bougainvillea plants.
The kinetics of wax ester synthesis from oleic acid and oleyl alcohol using immobilized lipase from Candida antartica as catalyst was studied with different types of impeller (Rushton turbine and AL-hydrofoil) to create different mixing conditions in 2l stirred tank reactor. The effects of catalyst concentration, reaction temperature, and impeller tip speed on the synthesis were also evaluated. Rushton turbine impeller exhibited highest conversion rate at lower impeller tip speed as compared to AL-hydrofoil impeller. A second-order reversible kinetic model from single progress curve for the prediction of fractional conversion at given reaction time was proposed and the corresponding kinetic parameter values were calculated by non-linear regression method. The results from the simulation using the proposed model showed satisfactory agreement with the experimental data. Activation energy shows a value of 21.77 Kcal/mol. The thermodynamic parameters of the process, enthalpy and entropy, were 21.15 Kcal/mol and 52.07 cal/mol.K, respectively.
Esterification of succinic acid with oleyl alcohol catalyzed by immobilized Candida antarctica lipase B (Novozym 435) was investigated in this study. Response surface methodology (RSM) based on a five-level, four-variable central composite design (CCD) was used to model and analyze the reaction. A total of 21 experiments representing different combinations of the four parameters including temperature (35-65°C), time (30-450 min), enzyme amount (20-400 mg), and alcohol:acid molar ratio (1:1-8:1) were generated. A partial cubic equation could accurately model the response surface with a R(2) of 0.9853. The effect and interactions of the variables on the ester synthesis were also studied. Temperature was found to be the most significant parameter that influenced the succinate ester synthesis. At the optimal conditions of 41.1°C, 272.8 min, 20 mg enzyme amount and 7.8:1 alcohol:acid molar ratio, the esterification percentage was 85.0%. The model can present a rapid means for estimating the conversion yield of succinate ester within the selected ranges.
Human sweet taste receptor (hSTR) recognizes a wide array of sweeteners, resulting in sweet taste perception. Maltitol and lactitol have been extensively used in place of sucrose due to their capability to prevent dental caries. Herein, several molecular modeling approaches were applied to investigate the structural and energetic properties of these two polyols/hSTR complexes. Triplicate 500 ns molecular dynamics (MD) simulations and molecular mechanics/generalized Born surface area (MM/GBSA)-based free energy calculations revealed that the TAS1R2 monomer is the preferential binding site for maltitol and lactitol rather than the TAS1R3 region. Several polar residues (D142, S144, Y215, D278, E302, R383, and especially N143) were involved in polyols binding through electrostatic attractions and H-bond formations. The molecular complexation process not only induced the stable form of ligands but also stimulated the conformational adaptation of the TAS1R2 monomer to become a close-packed structure through an induced-fit mechanism. Notably, the binding affinity of the maltitol/TAS1R2 complex (ΔGbind of -17.93 ± 1.49 kcal/mol) was significantly higher than that of the lactitol/TAS1R2 system (-8.53 ± 1.78 kcal/mol), in line with the experimental relative sweetness. These findings provide an in-depth understanding of the differences in the sweetness response between maltitol and lactitol, which could be helpful to design novel polyol derivatives with higher sweet taste perception.
Alcohol consumption is a risk factor for oral cancer, possibly via its conversion to acetaldehyde, a known carcinogen. The oral commensal yeast Candida albicans may be one of the agents responsible for this conversion intra-orally. The alcohol dehydrogenase (Adh) family of enzymes are involved in acetaldehyde metabolism in yeast but, for C. albicans it is not known which family member is responsible for the conversion of ethanol to acetaldehyde. In this study we determined the expression of mRNAs from three C. albicans Adh genes (CaADH1, CaADH2 and CaCDH3) for cells grown in different culture media at different growth phases by Northern blot analysis and quantitative reverse transcription polymerase chain reaction. CaADH1 was constitutively expressed under all growth conditions but there was differential expression of CaADH2. CaADH3 expression was not detected. To investigate whether CaAdh1p or CaAdh2p can contribute to alcohol catabolism in C. albicans, each gene from the reference strain C. albicans SC5314 was expressed in Saccharomyces cerevisiae. Cell extracts from an CaAdh1p-expressing S. cerevisiae recombinant, but not an CaAdh2p-expressing recombinant, or an empty vector control strain, possessed ethanol-utilizing Adh activity above endogenous S. cerevisiae activity. Furthermore, expression of C. albicans Adh1p in a recombinant S. cerevisiae strain in which the endogenous ScADH2 gene (known to convert ethanol to acetaldehyde in this yeast) had been deleted, conferred an NAD-dependent ethanol-utilizing, and so acetaldehyde-producing, Adh activity. We conclude that CaAdh1p is the enzyme responsible for ethanol use under in vitro growth conditions, and may contribute to the intra-oral production of acetaldehyde.
The substitution of the oxyanion Q114 with Met and Leu was carried out to investigate the role of Q114 in imparting enantioselectivity on T1 lipase. The mutation improved enantioselectivity in Q114M over the wild-type, while enantioselectivity in Q114L was reduced. The enantioselectivity of the thermophilic lipases, T1, Q114L and Q114M correlated better with log p as compared to the dielectric constant and dipole moment of the solvents. Enzyme activity was good in solvents with log p < 3.5, with the exception of hexane which deviated substantially. Isooctane was found to be the best solvent for the esterification of (R,S)-ibuprofen with oleyl alcohol for lipases Q114M and Q114L, to afford E values of 53.7 and 12.2, respectively. Selectivity of T1 was highest in tetradecane with E value 49.2. Solvents with low log p reduced overall lipase activity and dimethyl sulfoxide (DMSO) completely inhibited the lipases. Ester conversions, however, were still low. Molecular sieves employed as desiccant were found to adversely affect catalysis in the lipase variants, particularly in Q114M. The higher desiccant loading also increased viscosity in the reaction and further reduced the efficiency of the lipase-catalyzed esterifications.