Effects of Different Quinoid Redox Mediators on the Anaerobic Reduction of Azo Dyes by Bacteria

Abstract

The addition of quinoid redox mediators to anaerobically incubated cultures of various taxonomically different bacterial species resulted in significantly increased reduction rates for the azo dye amaranth. From different quinones tested, generally anthraquinone-2-sulfonate (AQS) and lawsone (2-hydroxy-1,4-naphthoquinone) caused the highest increase in the azoreductase activities. The effects of AQS and lawsone were studied in greater detail with Sphingomonas xenophaga BN6 and Escherichia coli K12. Both strains reduced the quinones under anaerobic conditions with significantly different relative activities. The chemically reduced forms of AQS, lawsone, and different other quinones were assayed for their ability to decolorize amaranth, and a good correlation between the redox potentials of the quinones and the reduction rates of the azo dyes was observed. The addition of AQS or lawsone also increased the ability of unacclimated sewage sludge to reduce azo dyes. Chemically pure lawsone could be replaced by the powdered leaves of the henna plant which contain significant amounts of lawsone.

Aplicação conjunta de tratamento anaeróbio termofílico por lodo granular e de mediadores redox na remoção de cor de águas residuárias têxteis

“…Na presença de AQS e AQDS sob condições termofílicas, os valores de k eram aumentados em 4,5 e 2,9 vezes, respectivamente. Rau et al (2002) também encontraram que o mediador redox AQS era mais efetivo to que AQDS na redução do corante Amarant pela cultura pura de Sphingomonas xenophaga BN6. Os últimos autores atribuíram tal observação ao valor mais negativo do potencial redox padrão (E 0 ') do AQS (-225 mV) comparado com AQDS (-184 mV), o que refletia uma melhor capacidade de transferência de elé-trons da sua forma reduzida para os corantes.…”

“…Tal transferência de elé-trons é usualmente o limitante do processo de redução (Lovley et al, 1996;Dos Santos et al, 2005). Vitaminas como riboflavina (Vitamina B2), e outras substâncias como as quinonas presentes em húmus e carvão ativado, podem funcionar como mediadores redox (Rau et al, 2002;Dos Santos et al, 2004). A remoção de cor na presença dessas substânci-as se dá em duas fases: a primeira fase consiste na redução enzimática do mediador redox através dos elétrons gerados nos processos oxidativos; e a segunda fase consiste na transferência química desses elétrons para os corantes azo, com a conseqüente regeneração dos mediadores redox (Figura 1) (Keck et al, 1997).…”

Stimulation of oxygen to bioanode for energy recovery from recalcitrant organic matter aniline in microbial fuel cells (MFCs)

“…However, it was still not clear the type of electron mediators, although the potential was in the range of the quinoid type (À0.3 Ve0.3 V) (Rau et al, 2002). Additionally, most of reported microbial produced electron mediator just showed one pair of redox peak in CV and some other revealed two-pair, such as riboflavin (Freguia et al, 2009;Mehta-Kolte and Bond, 2012;Rabaey et al, 2005).…”

Biological catalyzed denitrification by a functional electropolymerization biocarrier modified by redox mediator

“…The ORP values of NADPH/NADP + , NADH/NAD + and Q/ QH 2 are À324 mV, À320 mV, and 45 mV, respectively (Rau et al, 2002), and the ORP value of AQS is À218 mV (Kudlich et al, 1997), so the role of AQS may be similar to Q/QH 2 . The catalyzing mechanism of the redox mediator in denitrification needs to be studied in detail using cell extracts and purified enzymes, which would allow a better understanding of the nature of the process.…”