Thiocyanate degradation by pure and mixed cultures of microorganisms

Uma cultura mixta e uma linhagem bacteriana pura foram isoladas de um bioreator para tratamento de tiocianato. As culturas removeram 5mM de tiocianato do meio em 36 horas. A cultura mixta foi capaz de tolerar concentrações superiores a 60mM. A eficiência da degradação de tiocianato diminuiu quando as células foram imobilizadas.

Trehalose accumulation, invertase activity and physiological characteristics of yeasts isolated from 24 h fermentative cycles during the production of artisanal Brazilian cachaça

Trehalose accumulation, invertase activity and physiological characteristics of 86 yeast isolates from short fermentative cycles during the production of cachaça in three artisanal distilleries of the State of Minas Gerais were studied. Among these isolates, 70 percent were able to grow at temperatures between 40 and 42ºC. Only Saccharomyces cerevisiae isolates were able to grow over 40ºC. Lower temperatures (<40ºC) favoured the growth of yeasts such as Candida parapsilosis-like, C. maltosa-like, Kloeckera japonica, S. exiguus and C. bombicola-like. The isolates from all three distilleries were ethanol tolerant, produced invertase, and accumulate trehalose in the presence of glucose. The strains isolated from distillery A presented more resistance to ethanol (around 84.2 percent of the strains were able to grow in the presence of 12 percent ethanol) when compared to the ones from distilleries C and B (9.5 percent and no strain, respectively). The strains of S. cerevisiae isolated from the three distilleries presented a higher capacity to produce invertase and accumulate trehalose in the presence of glucose. Based on the results of thermal and ethanol stress experiments, it was possible to identify strong relationship between intracellular trehalose accumulation and cell viability. The increase in cell viability was even more pronounced when the strains were subjected to a pre-treatment at sublethal temperatures

Uptake of free and complexed silver ions by different strains of Rhodotorula mucilaginosa

Five strains of Rhodotorula mucilaginosa were tested for the ability to accumulate free and complexed silver ions by metabolism-dependent and -independent processes. The ability to take up Ag+ was observed in both live and dead biomass, whereas silver dicyanide [Ag (CN)2-] uptake was strictly glucose dependent. In contrast to Ag (CN)2-, glucose addition inhibited by 16 to 25(per cent) the Ag+ uptake rate of living UFMG - Y02, Y27, and Y35 cells, while strains CBS 316 and UFMG-Y01 showed an improved uptake rate of about 115(per cent) and 13(per cent), respectively. The Langmuir sorption model was used to evaluate the silver sorption capability of the R. mucilaginosa strains. The calculated qmax value suggested that R. mucilaginosa strains UFMG-Y27 had the highest loading capacity. The type strain CBS 316 had the lowest qmax but showed the highest affinity for silver ions. The results provided by the Fourier Transform Infra Red analysis (FTIR) suggest that C=O groups represent the main reactive site for silver uptake by the strain UFMG-Y27.