Use of photocatalytic reduction to hasten preparation of culture media for saccharolytic Clostridium species

Abstract

Cysteine is the preferred reducing agent used in the preparation of culture media for the growth of many strictly anaerobic microorganisms; however, redox potential reduction of cysteine is very slow, making it inconvenient if the medium is needed immediately or in large quantity. The time required to reduce culture medium containing resazurin (an indicator of reducing conditions) was dramatically shortened when the medium, after being injected with the reducing agent cysteine, was irradiated with incandescent light from a halogen lamp. Light intensity had an effect upon reduction time: tubes kept in the dark took more than 12 h to achieve the desired degree of anaerobiosis (measured spectrophotometrically by the bleaching of the indicator, resazurin) while tubes subjected to ordinary laboratory illumination were reduced in about 2 h. When exposed to maximum light intensity (equivalent to a regular 100 watt bulb lamp) tubes could be made anaerobic in less than 20 min. Cysteine was essential for the bleaching of resazurin. Evidence that adequate anaerobiosis was achieved by light irradiation was provided by the fact that four Clostridium strains and one Thermoanaerobacter strain displayed similar growth (measured by lag time, growth rate, and extent of growth) in media reduced under high intensity light or under normal laboratory illumination.

Rapid Screening of Antimicrobial Synthetic Peptides

“…Consequently it was concluded that the use of resazurin was inadequate in case of antibiotic peptides containing cysteine residues with free thiol groups, as they reduce resazurin to colourless hydroresorufin. That process is utilized, for example, in reducing media for cultivation of anaerobic organisms (Fukushima et al 2002 , 2003 ). Therefore, peptides with reducing properties vitiate the results.…”

Reducing agent can be omitted in the incubation medium of the batch in vitro fermentation model of the pig intestines

“…Ammonia is a metabolic disruptor due to its ability to inhibit mitochondrial oxygen consumption (Andriamihaja et al, 2010) and short-chain fatty acids (SCFA) oxidation (Cremin et al, 2003) in colonic epithelial cells. Moreover, the in vitro microbial activity could be influenced by the reducing agent as they can precipitate essential metal ions and produce potentially toxic intermediates that may induce an imbalance between bacterial species (Fukushima et al, 2003). Finally, reducing agents produce molecules that are also endproducts of intestinal protein fermentation, blunting the ability of in vitro methods to quantify the production of metabolites originating from protein fermentation.…”

Formulação à base de um extrato do chá verde desenvolvida para uso bucal: avaliação da atividade antimicrobiana e da alteração de cor dental

“…Além da seleção do meio de cultura, outra etapa importante no estudo in vitro é a seleção do revelador de crescimento bacteriano. No presente estudo foi utilizado o revelador resazurina (Resazurin sodium salt powder), um indicador de oxidação-redução, que tem sido utilizado por muito autores para avaliar a viabilidade celular e a contaminação bacteriana (Carter et al, 1998;Mann e Markham, 1998;Smith e Townsend, 1999;Fukushima et al, 2003;Saraiva, 2012). A mudança de cor de azul para rosa indica redução de resazurina e portanto presença de crescimento bacteriano, sendo assim determinada a CIM, ou seja, a menor concentração da droga que impede esta mudança de cor.…”