Comparative study of polyhydroxyalkanoates production from acidified and anaerobically treated brewery wastewater using enriched mixed microbial culture.

The production of polyhydroxyalkanoates (PHA) from wastewaters using microbial mixed cultures (MMC) has been attracting increased interest because of PHA's biodegradability characteristics. Production of PHA by an MMC enriched with PHA-accumulating bacteria was compared using anaerobically treated and acidified brewery wastewaters under various feeding strategies, namely pulse and batch feed addition. To obtain an enriched MMC, a sequencing batch reactor was inoculated with activated sludge fed with acetate and subjected to aerobic dynamic feeding. The enriched MMC was able to accumulate PHA up to 72.6% of cell dry weight (CDW) with pulse addition of acetate controlled by the dissolved oxygen (DO) concentration in the reactor. In a batch accumulation experiment with acetate, the PHA content achieved (28.5% CDW) was less than that of the pulse feeding strategy with the same amount of acetate (~2000 mg C/L). Using anaerobically treated and acidified brewery wastewater fed in pulses, the maximum PHA accumulated by the enriched MMC was similar for both wastewaters (45% CDW), in spite of the higher volatile fatty acid concentration in acidified brewery wastewater. The pulse feed addition controlled by the DO concentration was difficult to implement for wastewater as compared to acetate because the difference in DO concentration between substrate availability and depletion was low. For the batch addition of acidified wastewater, a slightly lower PHA content (39% CDW) was obtained. These results show that both brewery wastewaters can be utilized for PHA production with a similar maximum PHA storage capacity.

Ultrasensitive optical detection of hydrogen peroxide by triggered activation of horseradish peroxidase.

Hydrogen peroxide is a very reactive byproduct of many metabolic pathways. We describe an ultra-sensitive colorimetric method to detect hydrogen peroxide based on the reconstitution of apo-horseradish peroxidase with the hemin derivative, hemin di(N,N'-acetyl-hydrazide). Oxidation of the latter by hydrogen peroxide yields hemin, which is able to reconstitute apo-horseradish peroxidase, forming an active peroxidase. We have also applied this analyte-triggered reconstitution of horseradish peroxidase to detect the activity of the enzyme glucose oxidase.

Peptide-based SAMs that resist the adsorption of proteins.

In this paper we present a modular approach for the fabrication of surfaces to characterize protein-protein interactions. The approach is based on azido peptides with an optimized sequence which are then thiol-functionalized using an alkynyl thiol and "click" chemistry. From these peptide thiols we fabricated SAMs on gold to evaluate the protein resistance, using surface plasmon resonance spectroscopy, toward streptavidin, bovin serum albumin (BSA), and fibronectin.

Postformation Modification of SAMs: using click chemistry to functionalize organic surfaces.

We have investigated a recently established strategy of modifying organic surfaces exposed by thiolate SAMs (self-assembled monolayers) deposited on Au substrates by employing so-called click chemistry. This term is used to denote a modified Huisgen 1,3-dipolar cycloaddition. We demonstrate the potential of this method by coupling ferrocene and azido acetic acid to alkyne/azide-terminated SAMs. After the surface reaction, the modified organic monolayers were analyzed using infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Under the conditions used in this study, only for the azide-terminated SAMs could successful grafting of the ferrocene be achieved whereas for the alkyne-terminated SAMs the spectroscopic studies reveal a rather low yield of the coupling reaction.