Il lavoro artigiano nelle catene globali del valore

For the first time, whole microbial-cell biocatalysis method was successfully applied by us to the production of glucose esters by transesterification of glucose with vinyl propionate. Among ten bacterial and fungal strains tested, lyophilized cells of Pseudomonas stutzeri strain GIM 1.273 efficiently catalyzed the reaction with the highest conversion and initial rate. CNMR analysis showed that the reaction catalyzed by P. stutzeri yielded 6-O regiomer predominantly (>99%), clearly indicating high regioselectivity of the biocatalyst toward the 6-O-hydroxy group of glucose. Efficiency of the reaction catalyzed by lyophilized cells was evidently solvent-dependent. With the exception of acetonitrile-pyridine and tetrahydrofuran-pyridine systems, the substrate conversion rate clearly increased with increasing hydrophobicity of the organic solvent media used. The best results were obtained in isooctane-pyridine (3:7 v/v) system. Other optimal conditions were: water content 2% (v/v), molar ratio of the acyl donor to glucose 10:1, biocatalyst dosage 80mg/mL and reaction temperature 35°C, under which glucose conversion and reaction rate were 97.2% and 29.7mmol/Lh over the duration of 24h. A tenfold scale-up production of the 6-O-glucose ester further demonstrated that whole-cell P. stutzeri was an efficient and highly-regioselective alternative to purified enzymes for synthesis of glucose esters

Cellular Transport of Esculin and Its Acylated Derivatives in Caco‑2 Cell Monolayers and Their Antioxidant Properties in Vitro

Esculin has many pharmacological effects, but these are difficult to observe after oral administration owing to poor lipid solubility. In our previous study, five acylated derivatives with different acyl chain lengths (EA, EP, EO, EL, and EM) were synthesized to improve the lipophilicity of esculin. In this study, the bioavailability and antioxidant activity of the five derivatives were investigated. The logP of esculin, EA, EP, EO, EL, and EM were −1.1 ± 0.1, −0.3 ± 0.14, 0.1 ± 0.17, 1.6 ± 0.09, 2.4 ± 0.11, and 2.8 ± 0.18, and their <i>P</i>_app were 0.71 ± 0.02, 1.24 ± 0.18, 1.74 ± 0.11, 11.6 ± 3.6, 4.11 ± 1.03, and 2.64 ± 0.97 × 10^–6 cm/s, respectively. Besides, the bioavailability of EO, EL, and EM were seriously affected by carboxylesterase. The results of ABTS, ORAC, and DPPH assays indicated that the antiradical ability of the five derivatives did not exceed that of esculin. However, EA, EP, and EO showed more effective inhibition of AAPH-induced oxidative hemolysis than esculin did (<i>p</i> < 0.05), and EL and EM were less effective than esculin (<i>p</i> < 0.05). The mechanism was related to the distribution and localization of the derivatives in “oil–water interface” between the cytomembrane and the aqueous phase

Acylation of ara-C with vinyl laurate by <i>P. fluorescens</i> in different organic solvent systems^a.

a<p>The reaction conditions: 50 mg/mL biocatalyst, 20 mmol/L ara-C, 500 mmol/L VL, 40 µL water, 1 mL organic solvents, 30°C, 180 rpm and reaction time of 144 h.</p>b<p>The volume ratio of two organic solvent used, 1∶3 (v/v).</p

Influence of Organic Solvents on Catalytic Behaviors and Cell Morphology of Whole-Cell Biocatalysts for Synthesis of 5′-Arabinocytosine Laurate

<div><p>A whole-cell based method was developed for the regioselective synthesis of arabinocytosine laurate. Among the seven kinds of bacteria strains tested in the acylation reaction, <i>Pseudomonas fluorescens</i> gave the highest productivity and a higher 5′-regioselectivity than 99%. Compared with pure organic solvents, the use of organic solvent mixtures greatly promoted the yield of the whole-cell catalyzed reaction, but showed little influence on the 5′-regioselectivity. Of all the tested solvent mixtures, the best reaction result was found in isopropyl ether/pyridine followed by isopentanol/pyridine. However, the whole-cells showed much lower thermostability in isopropyl ether/pyridine than in THF-pyridine. To better understand the toxic effects of the organic solvents on <i>P. fluorescens</i> whole-cells and growing cells were further examined. Significant influences of organic solvents on the biomass of the cells were found, which differed depending on the type of solvents used. SEM analysis visually revealed the changes in the surface morphology of whole-cells and growing cells cultured in media containing various organic solvents, in terms of surface smoothness, bulges and changed cell sizes. Results demonstrated that organic toxicity to cell structure played an important role in whole-cell mediated catalysis.</p></div

Acylation of ara-C with vinyl laurate by various bacteria^a.

a<p>Reaction condition: 50 mg/mL whole cells, 20 mmol/L ara-C, 500 mmol/L VL, 40 µL water, 1 mL 25% (v/v) IPE-pyridine, 30°C,180 rpm. The data were obtained after 144 h reaction.</p>b<p>The bacteria were cultured at 30°C and 180 rpm for 48 h and then the harvested cells were pretreated by lyophilization for 24 h.</p>c<p>Not detected.</p

Solvent-sensitivity of the whole-cells in organic solvents (The whole-cells were kept in different mixture organic solvents under 30°C for 6 h before catalyzed the reaction).

<p>Solvent-sensitivity of the whole-cells in organic solvents (The whole-cells were kept in different mixture organic solvents under 30°C for 6 h before catalyzed the reaction).</p

Physicochemical, functional properties, and antioxidant activities of protein fractions obtained from mulberry (<i>morus atropurpurea</i> roxb.) leaf

<p>Mulberry leaf protein fractions were extracted by the ultrasonic cell disrupter-assisted Osborne method. The physicochemical, functional properties, and antioxidant activities of mulberry leaf protein fractions were investigated. Albumin and glutelin were the predominant fractions and contained higher contents of essential amino acids (above 300 g kg⁻¹). The solubility, water holding capacity, and emulsion stability of mulberry leaf protein fractions followed an order of albumin > globulin > glutelin > prolamin. All fractions exhibited significantly higher oil-holding capacity than soy protein isolates (<i>p</i> < 0.05). Furthermore, the radical scavenging activities of albumin were comparable to that of <i>L</i>-glutathione. Therefore, mulberry leaf protein fractions especially albumin showed encouraging functional properties and antioxidant activities, and could be considered as potential food ingredients and antioxidants.</p

SEM photographs of freeze-dried <i>P. fluorescens</i> cells after incubated in organic solvents for 24 h {a: PBS, b: DMF, c: IPE/pyridine (v/v = 1∶3), d: THF/pyridine (v/v = 1∶3)}, magnification was 10 K, scale bar: 1 µm.

<p>SEM photographs of freeze-dried <i>P. fluorescens</i> cells after incubated in organic solvents for 24 h {a: PBS, b: DMF, c: IPE/pyridine (v/v = 1∶3), d: THF/pyridine (v/v = 1∶3)}, magnification was 10 K, scale bar: 1 µm.</p