Bioflavonoids have many biological and pharmacological activities, but many of them display low bioavailability after oral administration owing to poor lipophilicity of glycoside forms. To improve their lipophilicity, as well as their bioactivity, a new efficient approach was developed for fatty acyl-modification of four vitamin P-like bioflavonoids (troxerutin, rutin, hesperidin, and naringin) using whole-cell biocatalysts in binary solvent systems. Using troxerutin as a typical important bioflavonoid, the acylation activities of 15 strains of different sources were evaluated and Pseudomonas aeruginosa GIM 1.46 showed the highest acylation activity in nonaqueous mediums. 13C NMR, ESI-MS, and FT-IR analysis confirmed that P. aeruginosa catalyzed acylation of troxerutin to produce troxerutin monopropionate (dominant product) and troxerutin dipropionate. In a binary system of n-heptane and pyridine, the cells showed much higher catalytic activity and operational stability than in other solvents, attributing to a proper increase in permeability of cell envelopes and cell viability by using the binary organic solvents. The optimal n-heptane concentration, molar ratio of vinyl propionate to troxerutin, catalyst dosage, and reaction temperature were found as 35%, 30:1, 50 mg/mL, and 40 °C, respectively, under which the troxerutin conversion and the monoester yield reached 94% and 81.1%, respectively.Keywords: Acylation; Biocatalysis; Organic solvent; Pseudomonas aeruginosa; Troxerutin;

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 Papp 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 (p < 0.05), and EL and EM were less effective than esculin (p < 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.Keywords: acylated derivatives; antioxidant; bioavailability; carboxylesterase; esculin;

As an important cellulose derivative, esterified cellulose nanocrystals (E-CNCs) could be applied in biomedical and chemical industries. A facile one-pot enzymatic method was proposed for the preparation of esterified cellulose nanocrystals with methyl laurate by using native cellulose as raw material in a binary ionic liquid (IL) system. 1-Butyl-3-methylimidazolium hydrogen sulfate ([BMIm]HSO4), a hydrophilic IL, acted as catalyst and solvent to produce cellulose nanocrystals (CNCs). 1-Butyl-3-methyl-imidazolium tetrafluoroborate ([BMIm][BF4]), which is hydrophobic, was used as a solvent for improving the lipase performance. The key reaction conditions, including mass ratio of [BMIm]HSO4/[BMIm][BF4], molar ratio of methyl laurate/anhydroglucose unit (AGU) in cellulose, mass ratio of lipase/cellulose, and reaction time, showed significant influences on the enzymatic transesterification of CNCs. The ester products were confirmed by FT-IR and 13C NMR analysis. The crystalline structure of E-CNCs was revealed by XRD. Compared with native cellulose, the E-CNCs showed improved crystallinity. TEM data showed the width of rod-shaped E-CNCs in the range of 10–30 nm. Compared to native cellulose, the thermal stability of E-CNCs was decreased due to the higher surface areas exposed to heat. This is the first successful preparation of E-CNCs with long-chain fatty acids from cheap native cellulose in a one-pot method.

Natural and nutrient substances for cardiovascular disease are promising and capture researchers’ minds. Two kinds of novel bioactive peptides (high Fischer’s ratio oligopeptides and anticoagulant peptides) were obtained from Whitmania pigra protein via enzymatic hydrolysis. An oligopeptide (MW<874.0 Da) named as HF2 was obtained via chromatography purification procedures with a high Fischer’s ratio of 31.92 ± 1.36 and low phenylalanine + tyrosine content of 0.98 ± 0.04 %. Another peptide (WA3-1), prepared by alcalase AF 2.4 L-catalyzed hydrolysis and then purified by DEAE Sepharose FF, gel Sephadex G-15 chromatography, exhibited high anticoagulant activity with prolonging significantly plasma clotting time on activated partial thromboplastin time, prothrombin time, thrombin time (p < 0.01) and powerful thrombolytic activity. Amino acid composition and MALDI-TOF/TOF MS analysis showed that WA3-1 contained 11 amino acids (MW: 1422.0 Da) with the sequence as NH2–His-Asp-Phe-Leu-Asn-Asn-Lys-Leu-Glu-Tyr-Glu–COOH. Abundant negatively charged amino acids in C-terminal, as well as the special residue Lys contribute to its anticoagulant capacity. This research provided a novel natural candidate for the manufacture of nutrient oligopeptides with high branched chain amino acid, and anticoagulant thrombolytic agent in pharmaceutical industry with helping prevent from thrombosis and related cardiovascular diseases.

Biocatalytic hydrolysis reactions were designed for preparation of bioactive hydrolysate of duck egg white protein (DEWP) employing two enzymes in one pot. Firstly, the fresh DEWP was thermal treated at 95 °C, for 40 min at pH 10, to effectively deactivate enzyme inhibitors thus facilitating the following two-step enzymatic hydrolysis. Compared with single-enzyme processes, the two-step enzymatic procedures showed much higher reaction efficiency. The first enzymatic step (in the presence of Alcalase or hydrolase SEEP) allowed to hydrolyze DEWP with degree of hydrolysis (DH) of 8.8–10 % and soluble peptide yield (SEP) of 60.5–70.2 % in a short period (4 h). The second enzymatic step (in the presence of Trypsin or Alcalase) gave a further degradation of DEWP with DH and SEP being more than 26.2 % and 90.4 %, respectively. The final hydrolysates exhibited high antioxidant activity in an evident DH dependent manner. The hydrolysates achieved by sequential addition of the proteinase SEEP and Alcalase at DH value 21 % gave the highest antioxidant activity, which was mainly ascribed to the changes in the amino acid compositions that the contents of some key amino acids and total hydrophobic amino acids were significantly improved by the enzymatic hydrolysis.

•Pulp fiber in papermaking was originally used for covalently immobilizing enzyme.•The procedures of oxidizing pulp fiber and coupling pectinase were simple.•The pectinase immobilized on oxidized pulp fiber showed good performance.Modified pulp fiber was originally used as a new type of carrier for pectinase immobilization. Pulp fiber was oxidized by sodium periodate to produce aldehyde groups for covalently binding with amino groups of pectinase. Results showed that the enzymatic activity of immobilized pectinase on pulp fiber reached 65 μg g−1 min−1 when immobilization pH value, temperature and time were of 7.0, 20 °C and 15 min, respectively. The immobilized pectinase showed higher thermo stability in a wider temperature range of 40–70 °C than its free type and its optimal pH shifted from 8.0 to 8.8. Furthermore, the immobilized pectinase exhibited good operational stability. When employed in whitewater treatment of papermaking industry, it still efficiently decreased the cationic demand after operating repeatedly for six batches. The results obtained demonstrate a promising route to prepare available, cheap and biodegradable carrier for immobilizing enzymes with potential application in wastewater treatment in papermaking industry.

Combined effects of key factors (pH value, extraction temperature, extraction time, salting out time) on extraction of pectin from banana peel was investigated by response surface methodology (RSM). When enriched in pectin, this research can be useful for preparation of banana products. Results showed that extraction temperature and time had the most significant combined effect on the improvement of extraction rate of pectin from banana peel, followed by the combined effects of extraction time and salting-out temperature. Besides, the extraction rate of pectin from banana peel also obviously affected by the interaction effects of pH and salting-out temperature. The fitted mathematical model allowed us to plot response surfaces and to determine optimal extraction conditions. Results showed that the optimum conditions were established for extraction of banana peel pectin: pH value 1.5, extraction temperature 85.5 °C, extraction time 2 h, and salting-out temperature 70.0 °C.

•Pulp fiber in papermaking was used for immobilizing enzyme after coated with PEI.•The procedure of immobilizing pectinase was simple, facile and inexpensive.•The thermo and pH stabilities of the enzyme were substantially enhanced.•The pectinase effectively reduced cationic demand of whitewater in papermaking.After being coated with polyethyleneimine (PEI), pulp fiber was used as carrier for pectinase. When PEI concentration, enzyme concentration and pH of enzyme solution were 0.01% (w/v), 0.25% (v/v) and 7, respectively, the resultant immobilized enzyme exhibited the highest enzymatic activity as about 670 μg min−1 g−1. Higher thermo and pH stabilities than those of the free enzyme were achieved after immobilizing the enzyme on PEI-coated pulp fiber. Furthermore, the bound pectinase effectively decreased the cationic demand of whitewater in papermaking under the practical industrial conditions and still maintained high activity after operating repeatedly for 8 batches. The results presented that through a simple, facile and inexpensive method, pectinase can be effectively immobilized on pulp fiber and the immobilized pectinase showed the potential application in practical industrial treatment of whitewater in papermaking industry.Download full-size image