Liquid−liquid flows in microchannels are important to microreactors/microfluidic devices that are used to carry out liquid−liquid reactions, extractions, emulsifications, etc. In this work, we report numerical investigations of drop/slug formation and flow regimes for liquid−liquid (oil−water) flow in microchannels. The Volume of Fluid (VOF) method was used to simulate the dynamics of water drop/slug formation in silicon oil, and the predicted drop/slug shapes/lengths were compared with previous literature measurements [Garstecki et al., Lab Chip
2006, 6, 437−446]. The effects of flow rates of water and oil phases (0.019−0.417 and 0.004−0.14 μL/s, respectively), channel size, liquid−liquid distributor (T-junction and Y-junction), and liquid viscosity on liquid−liquid flow regimes and slug lengths were investigated. The predicted drop/slug formation dynamics/slug lengths agreed satisfactorily with the aforementioned Garstecki et al. literature measurements for Q
water/Q
oil in the range of 0.1−1.7. However, for Q
w
a
t
e
r/Q
oil > 1.7, unlike the (long) slug flow reported in the aforementioned Garstecki et al. literature, a parallel flow was observed in the numerical simulations. The effect of wall adhesion (contact angle) on the flow regimes and slug lengths was also investigated. The experimentally validated computational model will be useful to simulate mixing, transport processes, and chemical reactions in microchannels.
Production characterization of serratiopeptidase (STP) enzyme by Serratia marcescens was the aim of this study. Serratia marcescens was allowed to grow in Tryptone Yeast Extract Glucose broth culture for the purpose of inducing STP (serrapeptase or serratiopeptidase) enzyme. The optimal conditions for STP production by Serratia marcescens were; 0.5 % substrate(Gelatin) concentration; 24 h incubation period; 32ºC incubation temperature and 6.0 pH ; the best buffer for production of STP enzyme was phosphate buffer. The best broth ingredient was tryptone; An optimum carbon sources was glucose; an optimum nitrogen source for STP enzyme production was tryptone; Valine was the best amino acids for the production of STP enzyme; the utilization of organic acids, acetic, citric, lactic acid decreased STP enzyme production at different concentrations above 3.0%. The STP enzyme was partially purified by ammonium sulfate precipitation and dialysis. The enzyme was found to have 52 KDa molecular weight by SDS -PAGE analysis. The STP enzyme activity increased as the increase in enzyme concentration. The data obtained emphasizes the possibility of production and purification of the microbial STP enzyme for application under industrial scale.
For
the optimum use of soyasaponins isolated from soybean cake
and to explore the potential anti-inflammatory agents from pentacyclic
triterpenes as natural food supplements, microbial transformation
of soyasapogenol A was carried out. Four strains of microbes, including Bacillus megaterium CGMCC 1.1741, Penicillium griseofulvum CICC 40293, Bacillus subtilis ATCC 6633, and Streptomyces griseus ATCC 13273, showed robust catalytic
capacity to the substrate. Preparative biotransformation and column
chromatographic purification led to the isolation of 10 novel and
1 reported metabolites. The structure elucidation was performed using
1D/2D NMR and HR-ESI-MS analytical method. Several novel tailoring
reactions, such as allyl oxidation, C–C double bond rearrangement,
hydroxylation, dehydrogenation, and glycosylation, were observed in
the biotransformation. In the follow-up bioassay, most of the metabolites
exhibited low cytotoxicity and potent inhibitory activity against
the production of nitric oxide (NO) in RAW 264.7 cells stimulated
by lipopolysaccharide. Especially compound 6 (3-oxo-11α,21β,22β,24-tetrahydroxy-olean-12-ene)
showed comparable activity to the positive control of quercetin with
an IC50 value of 16.70 μM. These findings provided
an experimental approach to achieve the derivatization of natural
aglycons in soybeans through microbial transformation for developing
potent anti-inflammatory food supplements.
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