Growth of Rhodosporidium toruloides Strain DBVPG 6662 on Dibenzothiophene Crystals and Orimulsion

Abstract

Strains DBVPG 6662 and DBVPG 6739 of Rhodosporidium toruloides, a basidiomycete yeast, grew on thiosulfate as a sulfur source and glucose (2 g liter ؊1 or 10.75 mM) as a carbon source. DBVPG 6662 has a defective sulfate transport system, whereas DBVPG 6739 barely grew on sulfate. They were compared for the ability to use dibenzothiophene (DBT) and related organic sulfur compounds as sulfur sources. In the presence of glucose as a carbon source and DBT as a sulfur source, strain DBVPG 6662 grew better than DBVPG 6739. In the presence of thiosulfate as a sulfur source, the two yeast strains did not use DBT, DBT-sulfone, benzenesulfonic acid, biphenyl, and fluorene. When the two strains were grown in the presence of glucose, strain DBVPG 6662 transformed 27% of the DBT present (10 M) at a rate of 0.023 mol liter ؊1 h ؊1 in 36 h. Traces of 2,2-dihydroxylated biphenyl were transiently accumulated under these conditions. When the same strain was grown on glucose in the presence of a higher concentration of DBT (0.5 g liter ؊1 ), mainly in an insoluble form, the whole surface of the DBT crystals was colonized by a thick mycelium. This adherent structure was imaged by confocal microscopy with fluorescent concanavalin A, a lectin that specifically binds glucose and mannose residues. When DBVPG 6662 was grown on glucose in the presence of a commercial emulsion of bitumen, i.e., orimulsion, 68% of the benzo-and dibenzothiophenes and DBTs was removed after 15 days of incubation. The fungus adhered by hyphae to orimulsion droplets. When cultivated in the presence of commercial emulsifier-free fuel oil containing alkylated benzothiophenes and DBTs and having a composition similar to that of orimulsion, strain DBVPG 6662 removed only 11% of the total organic sulfur that occurs in the medium and did not adhere to the oil droplets. These results indicate that strain DBVPG 6662 is able to utilize the organic sulfur of DBT and a large variety of thiophenic compounds that occur extensively in commercial fuel oils by physically adhering to the organic sulfur source.

Genomics of alternative sulfur utilization in ascomycetous yeasts

“…The ascomycetous yeast Candida digboiensis has been shown to desulfurise the heterocyclic organosulfur compound dibenzothiophene (DBT), although it not known whether this yeast can utilize DBT as its sole source of sulfur (Sood & Lal, 2009). Strains of the basidiomycetous yeast Rhodosporidium toruloides can utilize DBT as the sole sulfur source by directly adhering to the surface of DBT crystals in solution (Baldi et al, 2003). A number of studies have demonstrated the ability of lignindegrading fungi to desulfurise DBT and various other heterocyclic organosulfur compounds such as diphenylsulfide and thianthrene (Faison et al, 1991;Ichinose et al, 2002;Van Hamme et al, 2003).…”

Mobilidade de bário em solo tratado com sulfato de bário sob condição de oxidação e redução

“…Os resultados obtidos do fracionamento geoquímico demonstram, de forma clara, que a condição de redução proporcionou a redução dos teores de bário das frações mais estáveis (F2 e F4) e aumento na fração de maior labilidade (F1), aumentando o risco de contaminação ambiental. 10,31,32 Não há diferença significativa entre os teores de bário lixiviados nos diferentes pontos de coleta, ou seja, cada volume coletado dentro de cada dose ( Figura 1S, material suplementar), apresentando uma tendência de se manter, praticamente, constante entre o primeiro e o último volume coletado. Esse comportamento é, provavelmente, devido à baixa solubilidade do sulfato de bário (K ps = 1,1 x 10 -10 mol L -1 ) e ao equilíbrio químico do elemento em solução.…”

“…Diversos trabalhos evidenciam que em solos com valores baixos de Eh (< -220 mV) e na presença de BaSO 4, bactérias redutoras de sulfato são responsáveis pela solubilização e aumento do bário em solução. 10,34,35 A Figura 3 apresenta a quantidade de bário removido por cada volume coletado no lixiviado e o total removido em função das doses aplicadas e níveis de umidade. A remoção de bário ocorreu de forma diferenciada, principalmente, em função das doses aplicadas e aumentaram de forma significativa e linear.…”

“…7 Em ambientes com severa redução a solubilidade do sulfato de bário pode ser alterada. 8 Apesar da baixa solubilidade do sulfato de bário em solos, 9 alguns estudos indicam que a baritina (BaSO 4 ) poderá funcionar como fonte de sulfato na respiração de bactérias anaeróbicas, 8,10 podendo promover o aumento da solubilidade e liberação de Ba +2 no ambiente, potencializando a transferência desse elemento para a cadeia alimentar e a contaminação das águas subsuperficiais. 11,12 Em estudo realizado por Nogueira et al, 13 sobre o efeito de aplicações sucessivas de lodo de esgoto nos teores de bário no solo e plantas, verificaram que houve aumento na absorção do elemento pelas plantas, porém não em níveis que possam ser considerados tóxicos.…”

Utilization of dibenzothiophene as sulfur source by Microbacterium sp. NISOC-06

“…Thus, DBT has been as a model compound in desulfurization studies (Okada et al 2002a, b). Considering progress of biological reactions in mild conditions and inexpensiveness of microbial fermentation processes, Biocatalytic desulfurization (BDS) has been a main candidate as an alternative or complement desulfurization process (Baldi et al 2003;Gupta and Roychoudhury 2005;Lee et al 1995). Many studies have used traditional and the same techniques to detect DBT desulfurizing and/or degrading microorganisms by enrichment in aquatic systems and metabolic pathways have been elucidated for some of them (Baldi et al 2003;Gupta and Roychoudhury 2005;Kropp et al 1997;Okada et al 2002a, b;Rashidi et al 2006;Soleimani et al 2007).…”