Development of environmentally friendly coatings and paints using medium-chain-length poly(3-hydroxyalkanoates) as the polymer binder.

Unsaturated medium-chain-length poly(3-hydroxyalkanoates) (mcl-PHAs) produced by Pseudomonas putida from linseed oil fatty acids (LOFA) and tall oil fatty acids (TOFA), were used as the polymer binder in the formulation of high solid alkyd-like paints. The relatively high concentration of unsaturated alkyl side chains incorporated into the PHA resins resulted in oxidative drying PHA paints having excellent coating properties. The homogeneously pigmented PHA coatings yielded high-gloss, smooth and strong films upon curing and showed an excellent flexibility, a good adhesion to different substrates, cohesive film properties and resistance to chipping.     

Voltage-activated ionic channels and conductances in embryonic chick osteoblast cultures

Summary Patch-clamp measurements were made on osteoblast-like cells isolated from embryonic chick calvaria. Cell-attachedpatch measurements revealed two types of high conductance (100–250 pS) channels, which rapidly activated upon 50–100 mV depolarization. One type showed sustained and the other transient activation over a 10-sec period of depolarization. The single-channel conductances of these channel types were about 100 or 250 pS, depending on whether the pipettes were filled with a low K⁺ (3mm) or high K⁺ (143mm) saline, respectively. The different reversal potentials under these conditions were consistent with at least K⁺ conduction. Whole-cell measurements revealed the existence of two types of outward rectifying conductances. The first type conducts K⁺ ions and activates within 20–200 msec (depending on the stimulus) upon depolarizing voltage steps from <–60 mV to >–30 mV. It inactivates almost completely with a time constant of 2–3 sec. Recovery from inactivation is biphasic with an initial rapid phase (1–2 sec) followed by a slow phase (>20 sec). The second whole-cell conductance activates at positive membrane potentials of >+50 mV. It also rapidly turns on upon depolarizing voltage steps. Activation may partly disappear at the higher voltages. Its single channels of 140 pS conductance were identified in the whole cell and did conduct K⁺ ions but were not highly Cl^– or Na⁺ selective. The results show that osteoblasts may express various types of voltage controlled ionic channels. We predict a role for such channels in mineral metabolism of bone tissue and its control by osteoblasts.     

Voltage-activated ionic channels and conductances in embryonic chick osteoblast cultures

Patch-clamp measurements were made on osteoblast-like cells isolated from embryonic chick calvaria. Cell-attached-patch measurements revealed two types of high conductance (100-250 pS) channels, which rapidly activated upon 50-100 mV depolarization. One type showed sustained and the other transient activation over a 10-sec period of depolarization. The single-channel conductances of these channel types were about 100 or 250 pS, depending on whether the pipettes were filled with a low K+ (3 mM) or high K+ (143 mM) saline, respectively. The different reversal potentials under these conditions were consistent with at least K+ conduction. Whole-cell measurements revealed the existence of two types of outward rectifying conductances. The first type conducts K+ ions and activates within 20-200 msec (depending on the stimulus) upon depolarizing voltage steps from less than -60 mV to greater than -30 mV. It inactivates almost completely with a time constant of 2-3 sec. Recovery from inactivation is biphasic with an initial rapid phase (1-2 sec) followed by a slow phase (greater than 20 sec). The second whole-cell conductance activates at positive membrane potentials of greater than +50 mV. It also rapidly turns on upon depolarizing voltage steps. Activation may partly disappear at the higher voltages. Its single channels of 140 pS conductance were identified in the whole cell and did conduct K+ ions but were not highly Cl- or Na+ selective. The results show that osteoblasts may express various types of voltage controlled ionic channels. We predict a role for such channels in mineral metabolism of bone tissue and its control by osteoblasts.     

Sulphur and sulphate reduction with acetate and propionate in an aerobic process for sulphide removal

Summary Sulphide production rates of sulphur-and sulphate-reducing bacteria up to 50 mg per biomass support particle per day were observed in an aerated sulphide-removal reactor with polyurethane (PUR) foam as carrier material. The optimal pH and temperature for the sulphide-producing bacteria were 8.0 and 30°C respectively. Raschig rings and four types of cube-shaped PUR particles were tested as carrier materials. When using PUR particles, the sulphide production rate was always between 3% and 4% of the sulphide removal rate, dependent on the dimensions and pore size of the polyurethane support particles. With the Raschig rings this ratio was only 2% and for reactors in which no carrier materials were present it was even lower (0.6%). Media containing different mixtures of acetate, propionate, sulphur and sulphate inoculated under anoxic conditions with sludge from the aerated reactor showed the presence of acetate-degrading sulphur-reducing, but not of acetate-degrading sulphate-reducing, bacteria. With propionate as sole electron donor no degradation occurred in the presence of sulphur within 2 weeks, whereas sulphate-dependent propionate oxidation started after 5–6 days incubation. Bacteria were isolated and resembled Desulfuromonas acetoxidans and Desulfobulbus propionicus morphologically and physiologically.