Search

Androst-4-ene-3,17-dione (AD) is an important intermediate of steroid drugs, and the microbial side-chain cleavage of sterols to produce AD by Mycobacterium sp. has attracted much attention. Unfort...

Supercritical solution impregnation (SSI) was applied to prepare drug-loaded biodegradable films where poly(l-lactic acid) (PLLA) was used as the matrix and roxithromycin as the model drug. The eff...

Ginkgo flavonoids were extracted from Ginkgo biloba leaves using supercritical carbon dioxide extraction technology (SFE) with ethanol as the entrainer. The effects of important process parameters on SFE were examined, and the crude extracts were further refined. At optimized experimental conditions, i.e., 20 MPa of extraction pressure, a 40 °C extraction temperature, a 10 g/min CO2 flow rate, and a 6 mL/min ethanol flow rate, the extraction yield could reach 0.36%. Supercritical fluid assisted atomization introduced by a hydrodynamic cavitation mixer (SAA-HCM) was used to obtain microparticles of Ginkgo flavonoids. The influences of the solute concentration as well as the mass flow ratio of the CO2/liquid solution on particle size (PS) and particle size distribution (PSD) were investigated. Well-defined, spherical, and separated particles with a controlled particle size ranging between 0.2 and 3.0 μm were successfully obtained in this work. The micronization of Ginkgo flavonoids can improve the drug abso...

Microorganisms are inactivated remarkably by carbon dioxide at the elevated pressure. The process can be divided into two phases based on the different rate of inactivation: the rate of inactivation is slower at the initial stage and increased sharply at the later stage. The dissolution of CO 2 into the aqueous solution and then diffusion into cells controls the duration and inactivation rate at the early stage. An increase of pressure and temperature enhances the antimicrobial effect of CO 2 under pressure. Inactivation is also affected by agitation and release of pressure. Ethanol is an effective and novel aid to intensify inactivation of microorganisms in CO 2 . E. coli cells after CO 2 treatment are subjected to injury on membranes so as to lose salt tolerance and induce a leakage of intracellular materials. The changes of cell structure and inactivation of several enzymes are observed after treatment. But the most important inactivation mechanism may be the lowering of pH due to the penetration of CO 2 , which leads to the inhibition of certain metabolic and regulating processes.

The mass transfer behavior of solutes, including diffusion and membrane cutoff characteristics in capsules that were prepared by the interfacial reaction of sodium cellulose sulfate (NaCS) and poly(dimethyldiallyl-ammonium chloride) (PDMDAAC), was studied experimentally. By using the diffusion model developed, the diffusion coefficients of low-molecular-weight solutes, such as glucose, sucrose, ethanol, lactic acid, L-lysine, L-glutamic acid, L-tyrosine, L-tryptophan, and L-phenylalanine, in NaCS-PDMDAAC polyelectrolyte membrane were determined. The values of diffusion coefficients in the membrane were about 2-10% of those in pure water. The experimental results indicated that the encapsulation conditions, such as PDMDAAC concentration and PDMDAAC molecular weight, could affect the structure of NaCS-PDMDAAC membrane and further would lead to the change of diffusion coefficients of solutes in capsules. The molecular weight cutoff (MWCO) is less than 2 kDa, which indicates that the NaCS-PDMDAAC capsule membrane has good cutoff performance and can well obstruct the passing of the membrane by the high-molecular-weight solutes.

Asymmetric reduction of β-oxo ester to chiral β-hydroxy ester by yeast cells is one of the most promising routes for synthesis of chiral pharmaceutical intermediates. But the stereoselectivity and initial substrate concentration of this asymmetric reduction reaction are usually unsatisfactory. When asymmetric reduction of ethyl 4-chloro-3-oxobutanoate to chiral ethyl 4-chloro-3-hydroxybutanoate by baker's yeast was chosen as the model reaction, it was investigated to improve the stereoselectivity and initial substrate concentration of this asymmetric reduction reaction by introducing resin to slowly release the substrate and in situ adsorb the product. The experiments indicated that the stereoselectivity could be promoted from about 78% to 95% with this technique, and the initial substrate concentration could be increased from 70 to 150 mmol/L, but the yield and stereoselectivity were still satisfactory with introducing resin.

The activities of cellulase, α-amylase, and acid protease in ethanol + water at elevated CO2 pressure were investigated. The experimental results indicated that the operating conditions of under 30% (mass percent) ethanol concentration and lower than 35 °C were quite suitable for cellulase−ethanol−water systems using high-pressure CO2, but α-amylase treated with high-pressure CO2 was liable to denature. The results also showed that it was suitable to precipitate acid protease in high-pressure CO2 (upward 6.86 MPa) within a wide range of ethanol concentration (upward 50%) and temperature (under 60 °C).