Extraction of Saponins from Xanthoceras sorbifolium Bunge Leaves Using Deep Eutectic Solvents and Their Inhibitory Activity against Postharvest Pathogenic Fungi

To investigate the effect of deep eutectic solvents (DES) on the extraction of saponins from Xanthoceras sorbifolium Bunge leaves (XLs) and their antifungal properties, a total of 43 DES were utilized for the extraction. Among these, choline chloride:lactic acid (1:1) exhibited the highest yield was therefore chosen as the extraction solvent. Optimization of the extraction procedure was carried out through one-way and Box-Behnken experiments. The extracts were characterized using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The mechanism of XLs saponins extraction by DES was investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). Furthermore, the inhibitory effects of XLs saponins on six typical fungi that posed a threat to fruits and vegetables were evaluated. Results showed that under the conditions of DES concentration of 47.00%, liquid-solid ratio of 42.00 mL/g, and extraction temperature of 43.00 ℃, the yield of XLs saponin using DES reached 10.22%±0.28%, representing a 38.8% increase compared to traditional solvents. It was an extraction method of XLs saponin with great potential for application. The saponins extracted by DES from XLs mainly included madecassic acid, saikogenin D, glycyrrhetinic acid, oleanolic acid, ginsenoside Rg3, maslinic acid, saikosaponin A and asiatic acid. DES was observed to disrupt cell integrity and cell wall structure by dissolving lignin and hemicellulose components, facilitating the release and solubilization of saponins. Additionally, XLs saponin demonstrated effective inhibition of spores of Aspergillus niger, Rhizopus oryzae and Aspergillus flavus of three out of the six typical post-harvest pathogenic fungi of fruits and vegetables. Among the pathogenic fungi studied, the spore germination of Rhizopus oryzae was inhibited with the best effect, the inhibition rate reached 78.76%±2.56%, and XLs saponin inhibited the growth of the fungus by suppressing the antioxidant enzyme activity. These results suggest promising applications for XLs saponins in the postharvest preservation of fruits and vegetables

Purification and In Situ Immobilization of Papain with Aqueous Two-Phase System

Papain was purified from spray-dried Carica papaya latex using aqueous two-phase system (ATPS). Then it was recovered from PEG phase by in situ immobilization or preparing cross-linked enzyme aggregates (CLEAs). The Plackett-Burman design and the central composite design (CCD) together with the response surface methodology (RSM) were used to optimize the APTS processes. The highly purified papain (96–100%) was achieved under the optimized conditions: 40% (w/w) 15 mg/ml enzyme solution, 14.33–17.65% (w/w) PEG 6000, 14.27–14.42% (w/w) NaH2PO4/K2HPO4 and pH 5.77–6.30 at 20°C. An in situ enzyme immobilization approach, carried out by directly dispersing aminated supports and chitosan beads into the PEG phase, was investigated to recover papain, in which a high immobilization yield (>90%) and activity recovery (>40%) was obtained. Moreover, CLEAs were successfully used in recovering papain from PEG phase with a hydrolytic activity hundreds times higher than the carrier-bound immobilized papain

Low-Transition-Temperature Mixtures (LTTMs) for Dissolving Proteins and for Drug Formulation

Several diverse proteins are found to readily dissolve in neat low-transition-temperature mixtures (LTTMs). They undergo no irreversible denaturation in such unusual solvents, and the resistance of hen egg-white lysozyme against thermoinactivation in LTTMs is greater than in aqueous solution at extreme pHs. Separately, the water-sensitive drug aspirin is found to form concentrated transparent LTTMs, where it is some 10-fold more stable against cleavage than in water

Production of Fatty Acid Butyl Esters Using the Low Cost Naturally Immobilized <i>Carica papaya</i> Lipase

In this work, the low cost naturally immobilized Carica papaya lipase (CPL) was investigated for production of fatty acid butyl esters (FABE) to fulfill the aim of reducing the lipase cost in the enzymatic butyl-biodiesel process. The CPL showed specificities to different alcohol acyl acceptors. Alcohols with more than three carbon atoms did not have negative effects on the CPL activity. The CPL catalyzed butanolysis for FABE production was systematically investigated. The reaction solvent, alcohol/oil molar ratio, enzyme amount, reaction temperature, and water activity all affected the butanolysis process. Under the optimized conditions, the highest conversion of 96% could be attained in 24 h. These optimal conditions were further applied to CPL catalyzed butanolysis of other vegetable oils. All of them showed very high conversion. The CPL packed-bed reactor was further developed, and could be operated continuously for more than 150 h. All of these results showed that the low cost Carica papaya lipase can be used as a promising lipase for biodiesel production