D-Xylose fermentation, xylitol production and xylanase activities by seven new species of Sugiyamaella.

Sixteen yeast isolates identified as belonging to the genus Sugiyamaella were studied in relation to D-xylose fermentation, xylitol production, and xylanase activities. The yeasts were recovered from rotting wood and sugarcane bagasse samples in different Brazilian regions. Sequence analyses of the internal transcribed spacer (ITS) region and the D1/D2 domains of large subunit rRNA gene showed that these isolates belong to seven new species. The species are described here as Sugiyamaella ayubii f.a., sp. nov. (UFMG-CM-Y607T = CBS 14108T), Sugiyamaella bahiana f.a., sp. nov. (UFMG-CM-Y304T = CBS 13474T), Sugiyamaella bonitensis f.a., sp. nov. (UFMG-CM-Y608T = CBS 14270T), Sugiyamaella carassensis f.a., sp. nov. (UFMG-CM-Y606T = CBS 14107T), Sugiyamaella ligni f.a., sp. nov. (UFMG-CM-Y295T = CBS 13482T), Sugiyamaella valenteae f.a., sp. nov. (UFMG-CM-Y609T = CBS 14109T) and Sugiyamaella xylolytica f.a., sp. nov. (UFMG-CM-Y348T = CBS 13493T). Strains of the described species S. boreocaroliniensis, S. lignohabitans, S. novakii and S. xylanicola, isolated from rotting wood of Brazilian ecosystems, were also compared for traits relevant to xylose metabolism. S. valenteae sp. nov., S. xylolytica sp. nov., S. bahiana sp. nov., S. bonitensis sp. nov., S. boreocarolinensis, S. lignohabitans and S. xylanicola were able to ferment D-xylose to ethanol. Xylitol production was observed for all Sugiyamaella species studied, except for S. ayubii sp. nov. All species studied showed xylanolytic activity, with S. xylanicola, S. lignohabitans and S. valenteae sp. nov. having the highest values. Our results suggest these Sugiyamaella species have good potential for biotechnological applications.

Thermostable inulinases secreted by yeast and yeast-like strains from the Brazilian semi-arid region.

The use of inulinases provides an alternative to the chemical process of inulin hydrolysis to obtain fructose syrup, and can reduce processing steps, time, and costs in the food industry. The objective of this work was to screen the thermostable inulinases produced by yeast and yeast-like strains isolated from the Brazilian semi-arid region. Thermostability was studied at different temperatures (60 degrees C, 70 degrees C, 80 degrees C and 90 degrees C) and for increasing periods of time (0-50 min). Thirty-three microorganisms were tested, and 27 showed inulinase activity with specific activities ranging from 0.98 to 73.79 micromol/mg protein/min. Three strains (CCMB 300, CCMB327 and CCMB328) showed the desired combination of high specific activity and a small reduction in residual activity when submitted to heat treatment (>or=60 degrees C). Our results indicate that the inulinases produced by these three yeast strains from the Brazilian semi-arid region have great potential to be used for inulin hydrolysis in the food industry.

Influence of bacteria from the duodenal microbiota of patients with symptomatic giardiasis on the pathogenicity of Giardia duodenalis in gnotoxenic mice.

Recent studies have shown that the intestinal microbiota is essential for the pathogenicity but not for the multiplication of Giardia duodenalis in the intestinal lumen. The microbial components responsible for this phenomenon are not known. Twenty-eight facultative and three strictly anaerobic micro-organisms were isolated from the dominant duodenal microbiota of five patients with symptomatic giardiasis. The bacterial combinations from each patient were associated with groups (GN) of germ-free mice. Five days after the association, when their faecal populations ranged from 10(7) to 10(9) cfu/g, all groups were inoculated intragastrically with 10(5) viable trophozoites of G. duodenalis strain BT6. Two groups of germ-free (GF) and conventional (CV1) mice were also infected. Gnotobiotic animals were killed 10 days after infection and GF and CV1 animals were killed 10, 20 and 30 days after infection. More marked pathological alterations were detected in CV1 mice when compared with GF animals. Gnotobiotic animals showed intermediate pathological alterations between CV1 and GF mice. The CV1 and GF groups became infected by day 3 and faecal cyst levels were similar in both groups throughout the experiment. Total and G. duodenalis-specific IgA levels in the intestinal fluid and G. duodenalis-specific IgM and IgG levels in the serum increased during the infection and were higher in CV1 animals at all times tested when compared with GF mice. The present results confirm the stimulatory activity of the intestinal microbiota on the pathogenicity of G. duodenalis, and some combinations of microbial components of the dominant duodenal ecosystem from patients with symptomatic giardiasis can partially develop this function. However, none of these combinations was able to stimulate the protozoan pathogenicity in the same manner as the entire intestinal microbiota.