Preparation of Biocompatible Liquid Marbles Stabilized by Food-Grade Stearate Microparticle for Aerobic Bacteria Cultivation.

Liquid marble (LM), a non-stick drop coated with micro- or nano-scale particles, has great potential in a wide range of applications. LMs have an advantageous feature in which gas or vapor can freely transport through their particle shell; therefore, it makes them an ideal candidate to be utilized as microbioreactor containing aerobic microorganisms. In this study, safer and more biocompatible LMs were successfully prepared using a food-grade calcium stearate microparticle as a stabilizer. As the volume of core liquid increased, the height of LM increased and reached a constant value, as a similar trend has been reported in conventional LMs. The drying rate curve of the LMs confirmed that the LMs have a similar pattern with the drying of typical wet powders. The drying rate depended on the salt species in the core solution and the environmental humidity. For instance, in the case of MgCl2, by changing humidity from 40 to 80% RH, the lifetime of LMs (time in which the LM dried completely) was increased to about 900 min. This is nearly three times longer than those have no salt and at 40% RH. Model aerobic bacteria Bacillus subtilis has actively proliferated inside the LM during 24-h incubation. Comparing with the test tube cultivations under O2-rich stationary or O2 rich-shaken conditions, the cultivation in the LM system showed a higher proliferation than the test tube systems. As a conclusion, we demonstrated that the calcium stearate LM system would be an ideal candidate for safer and easily available microbioreactor containing aerobic bacteria.

Higher order structure of Mucor miehei lipase and micelle size in cetyltrimethylammonium bromide reverse micellar system.

The higher order structure of Mucor miehei lipase and micelle size in a cationic cetyltrimethylammonium bromide (CTAB) reverse micellar system was investigated. Circular dichroic (CD) measurement revealed that the lipase far-UV CD spectra changed markedly, going from buffer solution to the reverse micellar solution, and were very similar for any organic solvent used. The ellipticity of the solubilized lipase in the far-UV region markedly decreased with increasing water content (W(0): molar ratio of water to CTAB), indicating that the secondary structure of lipase changed with the water content. The linear correlation between the W(0) and the micelle size was obtained by measuring dynamic light scattering. From the linear correlation between the micelle size and W(0), the higher order structure of the solubilized lipase appears to be affected directly by the micellar interface. The species and concentration of alcohol as a cosurfactant had an inferior effect on lipase structure. Especially, at ratios of 1-pentanol to CTAB of less than 8, the secondary and tertiary structures of lipase were preserved in the reverse micelles. The CTAB concentration had little effect on the lipase structure in the micelles. The catalytic activity of the lipase solubilized in the CTAB reverse micelles increased with increasing the W(0).

Interesterification activity of Rhizopus delemar lipase in phospholipid microemulsions.

The interesterification of olive oil with palmitic acid catalyzed by Rhizopus delemar lipase was investigated in phospholipid microemulsion systems. Soybean lecithin was used as the amphiphilic component. The maximal reaction rate was obtained at a buffer pH of 5.5-6.0. The reaction rate was also dependent on the W(L) (= [H2O]/[lecithin]) value and attained a maximum at W(L)=5. The reaction rate reached a maximum at a palmitic acid concentration of 350 mM. The molar fraction of the interesterified product 1,3-dipalmitoyl-3-oleoyl glycerol (POP) in the olive oil was enhanced from 2.8 to 65.6 mol% after 24 h of the reaction.

Higher order structure of proteins solubilized in AOT reverse micelles.

The higher order structure of proteins solubilized in an bis(2-ethylhexyl) sulfosuccinate sodium (AOT) reverse micellar system was investigated. From circular dichroic (CD) measurement, CD spectra of cytochrome c, which is solubilized at the interface of reverse micelles, markedly changed on going from buffer solution to the reverse micellar solution, and the ellipticity values in the far- and near-UV regions decreased with decreasing the water content (W0: molar ratio of water to AOT), indicating that the secondary and tertiary structures of cytochrome c changed with the water content. The ellipticity of ribonuclease A, which is solubilized in the center of micellar water pool, in the near-UV region was dependent on W0 and became minimum when W0 of ca. 8 while the ellipticity in the far-UV region was almost constant, indicating that the tertiary structure of ribonuclease A was affected by the water content, but the secondary structure was conserved. The degree of curvature of the micellar interface appears to influence the protein structure because the reverse micelle size is linearly proportional to the W0 value. As evidence of this, when the micelle size was comparable to the protein's dimensions, the structures were more affected by the water content. Judging from the dependence of the factor influencing the protein structure on the protein species, the location of solubilized protein in reverse micelles is significantly related to whether the protein structure in the system is affected by the micellar interface. In the cases of cytochrome c and lysozyme, the ellipticity against W0 was dependent on the AOT concentration. In contrast, ribonuclease A gave very similar ellipticity values whatever the AOT concentration. In the n-hexane micellar system, cytochrome c exhibited lower ellipticity values and ribonuclease A in the lower W0 range (W0

Successful removal of p-quinone with chitosan in an aqueous phase in relation to degree of deacetylation.

Phenol oxidant is successfully removed by using chitosan particles in the aqueous phase. Removal of p-quinone by chitosan from crab shells was investigated kinetically from molecular weight (MW) of chitosan, deacetylation degree (DD) and reaction temperature. The rate constant assuming first-ordered reaction on removal of p-quinone in aqueous phase primarily depended on the MW of chitosan, not on the DD. Quantities of chitosan exceeding 5 x 10(5) MW are able to obtain a sufficiently high rate constant (10(-3) s(-1)). At higher temperatures, higher rate constants were obtained in the entire experimental MW and DD. The activation energy obtained was 43.8 kJ x mol(-1).

Liquid-liquid extraction of alpha-lactalbumin using reverse micellar organic solvent.

The liquid-liquid extraction of alpha-lactalbumin based on reverse micellar organic solvents was investigated. Forward extraction of the protein in the reverse micellar organic phase from aqueous feed solutions was strongly dependent on the initial pH of the feed solution and the complete forward extraction of 0.03 mM alpha-lactalbumin was successfully achieved at pH 6.0. The forward extraction percentage steeply decreased with increasing KCl concentration, while in the NaCl system the forward extraction was independent on the salt concentration below 1 M. From the circular dichroic measurement, higher order structure of the recovered alpha-lactalbumin through the extraction process was well preserved.