Express-Method for Determination of the Oxidizing Capacity of Activated Sludge and Its Biofilms in Pulp and Paper Mill

Microbial dehydrogenase activity can help to determine the oxidizing capacity of activated sludge. Here we propose an innovative and automated express-method based on rapid determination of dehydrogenase activity. The measurement is based on the rate of methylene blue reduction by living microbial cells in suspension. A single analysis takes 10 min. The method was adapted for biofilms immobilized on the floating carriers of industrial bioreactors and the kinetics of biological oxidation by activated sludge and biofilms was compared. New parameters were proposed to characterize the biological oxidation under low oxygen levels. The obtained make it possible to quickly determine the dehydrogenase activity of activated sludge and biofilms and promptly monitor the effectiveness of industrial biological wastewater treatment.

A new approach for microbiological characterization of activated sludge: from the sample to the biomolecular analysis

The growing biomass in the wastewater treatment plant is called "activated sludge"; usually it is mainly composed by bacteria (95%) and by Protozoa and Metazoans (5%). The sludge biological composition is a good indicator of the wastewater treatment plant state of health. In this study, an initial characterization of the microorganisms present in the activated sludge is carried out through DNA analysis.The aim of this activity is the development of the procedures for the characterization of the sludge of the biological oxidation lines, to identify microorganism throught a new approach using biomolecular analysis and the definition of new standard protocols.

Bioleaching of Pyrrhotite with Bacterial Adaptation and Biological Oxidation for Iron Recovery

The microbially mediated recovery of valuable metals contained in mining waste presents an economical alternative to conventional hydrometallurgical processes. In order to investigate the effect of bacterial adaptation and biological oxidation on bioleaching, the microbially mediated bioleaching of a pyrrhotite sample from mine waste, with indigenous bacteria existing in acid mine drainage, was studied. The indigenous bacteria were sub-cultured repeatedly for iron adaptation, and Acidithiobacillus ferrooxidans was identified as the dominant member of the microbial consortium. The point of zero charge (PZC) of pyrrhotite sampled from mine waste was determined as 3.0. The performance of bioleaching by contact and non-contact biological oxidation was compared by conducting bioleaching under different initial pH (pHini) conditions (2.8 and 3.2). Negatively charged bacteria could be attached onto the pyrrhotite, which has a positive surface charge at lower pHini (2.8) than the PZC (3.0). Bacteria attachment and corrosion pits on the surface of the pyrrhotite residues were observed at pHini of 2.8. Under bacteria-adapted conditions, the leaching concentration of Fe (44.2 mg/L) at pHini of 2.8 was 2.1 times greater than that (21.3 mg/L) at pHini of 3.2. Under non-adapted bacteria conditions, the extent of Fe leaching was not significantly different between the pHini of 2.8 and 3.2. This could be attributed to the fact that the adapted bacteria could more easily attach onto the pyrrhotite surfaces at pHini 2.8, allowing contact biological oxidation during the bioleaching experiments. We demonstrate here that the bioleaching of pyrrhotite could increase Fe recovery through bacterial adaptation and contact biological oxidation.

Photocatalytic and Biological Oxidation Treatment of Real Textile Wastewater

With rapidly growing urbanization and industrialization in developing countries, a large volume of wastewater is produced from industries that contain chemicals generating high environmental risks, which could affect health and socio-economic activities if not treated properly. In this study, the discoloration of wastewater containing azo dyes by chemical oxidation process combined with a biological treatment was evaluated and applied on real textile wastewater generated from one Ethiopian industrial site. The use of TiO2 as a photocatalyst and the effect of the addition of H2O2 on color removal were investigated. Photocatalysis was followed by aerobic biological treatment and their combination resulted in 93.3 and 90.4% removal of color and chemical oxygen demand (COD), respectively. These results revealed that the combination of photocatalytic and biological treatment approach shows a promising potential for the removal of color from real textile wastewater.

Microbial Oxidoreductases: Biotechnological and Synthetic Applications

Enzymes are biocatalysts responsible for driving all biochemical reactions in the cells. The enzymes determine the physiology of a cell and together regulate the growth and proliferation of cells in response to various environmental signals. The ability of cells to adapt and respond to environmental conditions can be utilized for industrial applications. Hydrolases and oxidoreductases are the most common classes of enzymes used in various industries such as pharmaceutical, food and beverages, bioremediation and biofuels, among others. Oxidoreductases are the EC1 class enzymes that catalyze the biological oxidation and reduction reactions. They transfer electrons from one molecule (reductant that donates electron) to other molecules (oxidants those accept electron). Usually, the enzymes of this class are NAD+ (Nicotinamide Adenine Dinucleotide) or NADP (Nicotinamide Adenine Dinucleotide Phosphate)-dependent. The oxidoreductases are a diverse class of enzymes responsible for catalyzing highly stereo selective and regioselective reactions, because of which they are the enzymes of choice for synthesis of optically-active compounds. Alcohol dehydrogenase (ADH) is one of the most studied oxidoreductases. Generally, ADHs have narrow specificity towards their substrates. Here we are looking for ADH having high/ broad specificity towards the substrate. This review discusses the enzyme oxidoreductase, synthetic transformation with oxidoreductase and application of oxidoreductase in bioremediation.