Formation of amphiphilic poly(ethylene glycol)-b-polylactide (PEG/PLA) block copolymers was accomplished by using potassium alkoxides to initiate the anionic polymerization of ethylene oxide, with the living chain end initiating the polymerization of lactide. By using potassium 3,3-diethoxypropoxide as an initiator, block copolymers with an acetal moiety at the PEG chain end, which was later converted into an aldehyde group, were obtained. The amphiphilic block copolymers formed micelles in aqueous milieu. The conversion of acetal end groups to aldehyde groups was carried out by an acid treatment using 0.01 mol L-1 hydrochloric acid. The extent of the conversion attained was >90%, without any side reaction such as aldol condensation. The micellar structure may play an important role in preventing a possible aldol condensation between the neighboring two aldehyde groups at the PEG chain end. From dynamic light scattering measurements, no angular dependence of the scaled characteristic line width was observed in the case of the acetal-PEG/PLA(52/56) micelle, suggesting the spherical structure. The diameter and polydispersity factor of the polymeric micelle were influenced by the molecular weights and the composition of two components of the block copolymer. The block copolymer with the molecular weight of 5200 for PEG and 5600 for PLA was a most suitable balance for micelle formation with narrow distribution. Actually, the diameter and polydispersity factor (μ/Γ2) of acetal-PEG/PLA(52/56), determined by a cumulative method, were 33 nm and 0.03, respectively. No change in the micelle size and shape was observed before and after the conversion of the acetal end groups to aldehyde groups on the micelle. The critical micelle concentrations (cmc) of the polymeric micelle was 2−4 mg L-1, as determined by fluorescence spectroscopy using pyrene. This functionalized micelle, in particular the one carrying terminal aldehyde groups, is expected to have a wide utility not only in biomedical applications (e.g., drug delivery, diagnosis, and surface modification through the coupling of bioactive substances), but also for the construction of the supramolecular architecture.

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During the production of biodiesel, crude glycerol is produced as a byproduct at 10% (w/w). Clostridium pasteurianum has the inherent potential to grow on glycerol and produce 1,3-propanediol and butanol as the major products. Growth and product yields on crude glycerol were reported to be slower and lower, respectively, in comparison to the results obtained from pure glycerol. In this study, we analyzed the effect of each impurity present in the biodiesel-derived crude glycerol on the growth and metabolism of glycerol by C. pasteurianum. The crude glycerol contains methanol, salts (in the form of potassium chloride or sulfate), and fatty acids that were not transesterified. Salt and methanol were found to have no negative effects on the growth and metabolism of the bacteria on glycerol. The fatty acid with a higher degree of unsaturation, linoleic acid, was found to have strong inhibitory effect on the utilization of glycerol by the bacteria. The fatty acid with lower or no degrees of unsaturation such as stearic and oleic acid were found to be less detrimental to substrate utilization. The removal of fatty acids from crude glycerol by acid precipitation resulted in a fermentation behavior that is comparable to the one on pure glycerol. These results show that the fatty acids in the crude glycerol have a negative effect by directly affecting the utilization of glycerol as the carbon source, and hence their removal from crude glycerol is an essential step towards the utilization of crude glycerol.

All implants produced some alteration of the retina, but there were clear differences among the materials in the degree to which their presence disturbed the normal anatomy of the retina or RPE or incited tissue reactions around the implant.

A new natural-synthetic hybrid biomaterial has been isolated from the growth of Pseudomonas oleovorans in the presence of diethylene glycol (DEG). DEG was consumed by P. oleovorans with 20 mM sodium octanoate in modified E* medium, but its presence in the fermentation medium retarded cell growth and viability, influencing production and composition of polyhydroxyalkanoates with medium chain length substituents (mclPHAs) and consequently attenuating PHA yield. DEG affected the composition of the mclPHA with an increase in the C8 component: polyhydroxyoctanoate (PHO). Gas chromatography-mass spectrometry (GC-MS) was used to quantitatively monitor DEG in the system and reveal its cellular adsorption and penetration. Intracellularly, the DEG significantly reduced the molar mass of the mclPHA; PHO with a bimodal distribution of high and low molecular weight fractions was observed. 1H NMR, 2-D COSY, and heteronuclear single quantum coherence spectra confirmed that the high molecular weight fraction consisted of PHO chains terminated by DEG. Thus, the synthesis of this natural-synthetic hybrid copolymer, PHO-DEG, opens the way for microbial synthesis of a wide variety of PHA-DEG copolymers with a range of bioactive properties.