Improved synthesis of the antifungal isobutyl o-coumarate catalyzed by the Aspergillus terreus type B feruloyl esterase

BACKGROUND Hydroxycinnamic acids and some of their derivatives are molecules with interesting biological activities; for instance, hydroxylated hydroxycinnamic esters have proved to have antifungal properties, and thus the generation of these molecules is of industrial importance. In this study, the direct esterification capacity of the pure recombinant type B feruloyl esterase from Aspergillus terreus (AtFAE B) was evaluated by its ability to catalyze the synthesis of isobutyl o-coumarate, an interesting antifungal molecule. A ternary solvent system (isooctane/isobutanol/water) was employed to improve the synthesis of isobutyl o-coumarate, assessing different substrate concentrations, enzyme load, water percentages and pH and temperature values. RESULTS AtFAE B showed the highest initial rate at 18% (v/v) isobutanol and 50 mM o-coumaric acid, 0.04 mg/ml of enzyme, 4% (v/v) water without buffer and 40C. AtFAE B half-lives at 30C, 40C and 50C were 16.5 h, 1.75 h and 3.5 min, respectively. Thus, we decided to evaluate the bioconversion yield at 30C, where the enzyme showed the highest operational stability. At this temperature, we obtained a yield of ~80% after only 8 h of reaction, using a 78:18:4 isooctane:isobutanol:water ternary solvent system, with 50 mM of o-coumaric acid.CONCLUSIONS Under these improved conditions, the productivity was 1.06 g isobutyl o-coumarate/L*h with a biocatalyst yield of 209.6 kg isobutyl o-coumarate/kg free AtFAE B, demonstrating the promising potential of AtFAE B to accept the non-canonical o-coumaric acid as the substrate and to achieve the synthesis of isobutyl o-coum

Extraction and in vitro antioxidant activity of exopolysaccharide by Pleurotus eryngii SI-02

The extraction parameters for Pleurotus eryngii SI-02 exopolysaccharide (EPS) produced during submerged culture were optimized using response surface methodology (RSM). The optimum conditions for EPS extraction were predicted to be, precipitation time 20.24 h, ethanol concentration 89.62% and pH 8.17, and EPS production was estimated at 7.27 g/L. The actual yield of EPS under these conditions was 7.21 g/L. The in vitro antioxidant results of the EPS showed that the inhibition effects of EPS at a dosage of 400 mg/L on hydroxyl, superoxide anion and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals were 59.63 ± 3.72%, 38.69 ± 2.59%, and 66.36 ± 4.42%, respectively, which were 12.74 ± 1.03%, 8.01 ± 0.56%, and 12.19 ± 1.05% higher than that of butylated hydroxytoluene (BHT), respectively. The reducing power of EPS of P. eryngii SI-02 was 0.98 ± 0.05, 60.66 ± 5.14% higher than that of BHT. The results provide a reference for large-scale production of EPS by P. eryngii SI-02 in industrial fermentation and the EPS can be used as a potential antioxidant which enhances adaptive immune responses.

An oxidant and organic solvent tolerant alkaline lipase by P. aeruginosa mutant: downstream processing and biochemical characterization

An extracellular alkaline lipase from Pseudomonas aeruginosa mutant has been purified to homogeneity using acetone precipitation followed by anion exchange and gel filtration chromatography and resulted in 27-fold purification with 19.6% final recovery. SDS-PAGE study suggested that the purified lipase has an apparent molecular mass of 67 kDa. The optimum temperature and pH for the purified lipase were 45°C and 8.0, respectively. The enzyme showed considerable stability in pH range of 7.0-11.0 and temperature range 35-55 °C. The metal ions Ca2+, Mg2+ and Na+ tend to increase the enzyme activity, whereas, Fe2+ and Mn2+ ions resulted in discreet decrease in the activity. Divalent cations Ca+2 and Mg+2 seemed to protect the enzyme against thermal denaturation at high temperatures and in presence of Ca+2 (5 mM) the optimum temperature shifted from 45°C to 55°C. The purified lipase displayed significant stability in the presence of several hydrophilic and hydrophobic organic solvents (25%, v/v) up to 168 h. The pure enzyme preparation exhibited significant stability and compatibility with oxidizing agents and commercial detergents as it retained 40-70% of its original activities. The values of Km and Vmax for p-nitrophenyl palmitate (p-NPP) under optimal conditions were determined to be 2.0 mg.mL-1 and 5000 μg.mL-1.min-1, respectively.

Gender differences in the metabolism of benzene, toluene and trichloroethylene in rat with special reference to certain biochemical parameters.

Metabolites viz. phenol, hippuric acid and total trichloro compounds of benzene, toluene and trichloroethylene respectively were estimated in the urine samples of male and female rats after exposure for a period of 30 days. The results exhibited higher metabolism in female rats than the male rats. Their metabolism might be regulated by cytochrome P450 isozymes in a gender specific manner. However, sex differences in the activity of glutathione-S-transferases of the liver have also been found to determine their toxicity. Results have been discussed with quantitative profiles of other enzymes established in the liver of male and female rats.