Enzymatic reduction of azo and indigoid compounds

A customer- and environment-friendly method for the decolorization azo dyes was developed. Azoreductases could be used both to bleach hair dyed with azo dyes and to reduce dyes in vat dyeing of textiles. A new reduced nicotinamide adenine dinucleotide-dependent azoreductase of Bacillus cereus, which showed high potential for reduction of these dyes, was purified using a combination of ammonium sulfate precipitation and chromatography and had a molecular mass of 21.5 kDa. The optimum pH of the azoreductase depended on the substrate and was within the range of pH 6 to 7, while the maximum temperature was reached at 40°C. Oxygen was shown to be an alternative electron acceptor to azo compounds and must therefore be excluded during enzymatic dye reduction. Biotransformation of the azo dyes Flame Orange and Ruby Red was studied in more detail using UV-visible spectroscopy, high-performance liquid chromatography, and mass spectrometry (MS). Reduction of the azo bonds leads to cleavage of the dyes resulting in the cleavage product 2-amino-1,3 dimethylimidazolium and N∼1∼,N∼1∼-dimethyl-1,4-benzenediamine for Ruby Red, while only the first was detected for Flame Orange because of MS instability of the expected 1,4-benzenediamine. The azoreductase was also found to reduce vat dyes like Indigo Carmine (C.I. Acid Blue 74). Hydrogen peroxide (H2O2) as an oxidizing agent was used to reoxidize the dye into the initial form. The reduction and oxidation mechanism of Indigo Carmine was studied using UV-visible spectroscopy

Dissipation and recycling: What losses, what dissipation impacts, and what recycling options?

This chapter describes the activities in the Dissipation and Recycling Node of Global TraPs, a multistakeholder project on the sustainable management of the global phosphorus (P) cycle. Along the P supply and demand chain, substantial amounts are lost, notably in mining, processing, agriculture via soil erosion, food waste, manure, and sewage sludge. They are not only critical with respect to wasting an essential resource, but also contribute to severe environmental impacts such as eutrophication of freshwater ecosystems or the development of dead zones in oceans. The Recycling and Dissipation Node covers the phosphorus system from those points where phosphate-containing waste or losses have occurred or been produced by human excreta, livestock, and industries. This chapter describes losses and recycling efforts, identifies knowledge implementation and dissemination gaps as well as critical questions, and outlines potential transdisciplinary case studies. Two pathways toward sustainable P management are in focus: To a major goal of sustainable P management therefore must be to (1) quantify P stocks and flows in order to (2) identify key areas for minimizing losses and realizing recycling opportunities. Several technologies already exist to recycle P from different sources, including manure, food waste, sewage, and steelmaking slag; however, due to various factors such as lacking economic incentives, insufficient regulations, technical obstacles, and missing anticipation of unintended impacts, only a minor part of potential secondary P resources has been utilized. Minimizing losses and increasing recycling rates as well as reducing unintended environmental impacts triggered by P dissipation require a better understanding of the social, technological, and economic rationale as well as the intrinsic interrelations between nutrient cycling and ecosystem stability. A useful approach will be to develop new social business models integrating innovative technologies, corporate strategies, and public policies. That requires intensive collaboration between different scientific disciplines and, most importantly, among a variety of key stakeholders, including industry, farmers, and government agencies

Changes in freshwater organic matter fluorescence intensity with freezing/thawing and dehydration/rehydration

The effects of photodegradation and biodegradation upon aquatic organic matter lability have been extensively researched in all aquatic systems because of the impact of these. processes upon carbon cycling, with most studies undertaken on the dissolved organic fraction. Little research has been published into the effect of freezing/thawing and dehydration/rehydration although these are mechanisms which are often encountered in nature. In this work, 13 freshwaters from central England were analyzed for chemical water quality, total organic carbon, and organic matter fluorescence using excitation-emission- matrices (EEMs). Samples were stored unfiltered under dehydrated or frozen conditions, then rehydrated or thawed, and analyzed for fluorescence over five cycles. The effect of freezing/thawing and dehydration/rehydration upon total organic matter fluorescence was assessed through changes in fluorescence intensity of four common peaks measured on the EEM spectra. Sample spectra were found to respond in a sample specific manner after one and five cycles of analysis; although fluorescence intensity generally decreased, the magnitude of decrease was variable between fluorescence peaks and samples. Freezing/thawing and dehydration/rehydration provide useful information on the sensitivity of freshwater organic matter fluorescence to these environmental processes. Copyright 2009 by the American Geophysical Union

Fate of trace metals in anaerobic digestion

© Springer International Publishing Switzerland 2015. A challenging, and largely uncharted, area of research in the field of anaerobic digestion science and technology is in understanding the roles of trace metals in enabling biogas production. This is a major knowledge gap and a multifaceted problem involving metal chemistry; physical interactions of metal and solids; microbiology; and technology optimization. Moreover, the fate of trace metals, and the chemical speciation and transport of trace metals in environments— often agricultural lands receiving discharge waters from anaerobic digestion processes— simultaneously represents challenges for environmental protection and opportunities to close process loops in anaerobic digestion.The authors acknowledge funding within the framework of the COST Action 1302 (‘European Network on Ecological Roles of Trace Metals in Anaerobic Biotechnologies’). GC is supported by a European Research Council Starting Grant (‘3C-BIOTECH; No. 261330).Peer Reviewe