Hexavalent chromium （Cr（VI）） pollution has become one of the most serious environmental problems today. One removal strategy comprises the microbial reduction of Cr（VI）, is regarded as a cost-effective biotechno...Hexavalent chromium （Cr（VI）） pollution has become one of the most serious environmental problems today. One removal strategy comprises the microbial reduction of Cr（VI）, is regarded as a cost-effective biotechnology for the treatment of high volume and low concentration complex wastewaters. In this work a yeast strain that exhibits high Cr（VI） resistance was isolated from soil sediment. The isolated yeast was identified as Pichia anomala by sequencing analysis. The yeast showed a remarkable capacity to completely reduce 25 and 50 mg/L of Cr（VI） in 48 h under aerobic conditions. The increase of initial Cr（VI） concentration influenced reduction, growth and specific growth rate. This strain also exhibited multiple heavy metal tolerance. The presence of anions and cations in the medium had a great influence on chromium reduction. Fractionation of the cells showed that the mechanism of Cr（VI） removal by this strain is ＂adsorption-coupled reduction＂ and the hexavalent chromate reductase activity was expressed constitutively. FTIR analysis of the biomass exposed to chromium showed that the binding process of the chromium ions involves the active participation of functional groups present in the external surface of biomass. High Cr（VI） concentration resistance and high Cr（VI） reducing ability of this strain make it a suitable candidate for bioremediation.展开更多
Diversity of yeasts in association with bees and their food sources has been explored during the last decade.In Thailand,there has been no study of yeast identification in honey and bees.Hence,a total of 186 yeast str...Diversity of yeasts in association with bees and their food sources has been explored during the last decade.In Thailand,there has been no study of yeast identification in honey and bees.Hence,a total of 186 yeast strains were isolated from 37 honey samples of 12 different bee species.On the basis of morphological and physiological characteristics,55 representative strains were chosen and identified by sequence analysis of the 26S rDNA D1/D2 domain and the ITS region.The data were compared with the published sequences and the results showed the occurrence of 19 ascomycetous and 1 basidiomycetous yeast species.Six strains of the new species were isolated.Phylogenetic analysis of the 26S rDNA D1/D2 sequence revealed that they were conspecific and most closely related to Zygosaccharomyces mellis.Based on the ITS sequence,the new species was clustered with the type"and clearly distinguished from the type!.Sequence analysis of combined ITS-26S rDNA D1/D2 showed similar results.The occurrence of these two types,with a divergence of more than 1%in their sequences,and low DNA relatedness among them suggested that members of the typeβcan be regarded as separate species.An analysis of the morphological and physiological characteristics was performed.Ascospore formation was observed on acetate agar and Gorodkowa agar.The new Zygosaccharomyces species differed physiologically from Z.mellis in 4 assimilation tests.This data supports the hypothesis that the new species,Zygosaccharomyces siamensis,is a novel ascosporogenous yeast.The type strain is JCM 16825T(=CBS 12273T)and a description is given here.展开更多
Camel milk is traditionally considered to have medicinal characteristics that it has potential health benefits and could help to treat several illnesses. Particularly, it is closest to human breast milk and has high l...Camel milk is traditionally considered to have medicinal characteristics that it has potential health benefits and could help to treat several illnesses. Particularly, it is closest to human breast milk and has high levels of nutrients and bioactive components. The aim of this study was to explore the antioxidant peptides derived from protein fractions of camel milk. Camel milk proteins(CMP) were fractionated into camel casein protein(CCP) and camel whey protein(CWP), which were hydrolyzed with pepsin to produce peptic digests P-CCP and P-CWP, respectively. RP-HPLC was used for fractionation of the peptides from the P-CCP and P-CWP. The antioxidant activities were evaluated using superoxide anion generating system of xanthine oxidase(XOD)and 2,2-diphenyl-1-picrylhydrazyl(DPPH) scavenging assay. Active peptides were analyzed using matrixassisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF-MS) whereas a number of antioxidant peptides, with masses ranging from 913 to 2,951 Da, derived mainly from alpha-casein, lactophorin and lactoferrin, were identified. When yeast cells are used as a system for modeling mitochondrial disease, the peptides in caseins and whey fractions significantly enhanced the tolerance of yeast cells against peroxide-induced oxidative stress. The results show that both caseins and whey proteins of camel milk possess bioactive peptides with significant radical-scavenging activities and thus herald a fascinating opportunity for their potential as nutraceuticals or therapeutic peptides for prevention and treatment of oxidative stress-associated diseases.展开更多
文摘Hexavalent chromium （Cr（VI）） pollution has become one of the most serious environmental problems today. One removal strategy comprises the microbial reduction of Cr（VI）, is regarded as a cost-effective biotechnology for the treatment of high volume and low concentration complex wastewaters. In this work a yeast strain that exhibits high Cr（VI） resistance was isolated from soil sediment. The isolated yeast was identified as Pichia anomala by sequencing analysis. The yeast showed a remarkable capacity to completely reduce 25 and 50 mg/L of Cr（VI） in 48 h under aerobic conditions. The increase of initial Cr（VI） concentration influenced reduction, growth and specific growth rate. This strain also exhibited multiple heavy metal tolerance. The presence of anions and cations in the medium had a great influence on chromium reduction. Fractionation of the cells showed that the mechanism of Cr（VI） removal by this strain is ＂adsorption-coupled reduction＂ and the hexavalent chromate reductase activity was expressed constitutively. FTIR analysis of the biomass exposed to chromium showed that the binding process of the chromium ions involves the active participation of functional groups present in the external surface of biomass. High Cr（VI） concentration resistance and high Cr（VI） reducing ability of this strain make it a suitable candidate for bioremediation.
基金This work was funded by the Thai Government Science and Technology Scholarship for Ph.D.Study,awarded to S.Saksinchai,grant RSA5280010 from the Thailand Research Fund,the National Research University,and Office of the Higher Education Commission.
文摘Diversity of yeasts in association with bees and their food sources has been explored during the last decade.In Thailand,there has been no study of yeast identification in honey and bees.Hence,a total of 186 yeast strains were isolated from 37 honey samples of 12 different bee species.On the basis of morphological and physiological characteristics,55 representative strains were chosen and identified by sequence analysis of the 26S rDNA D1/D2 domain and the ITS region.The data were compared with the published sequences and the results showed the occurrence of 19 ascomycetous and 1 basidiomycetous yeast species.Six strains of the new species were isolated.Phylogenetic analysis of the 26S rDNA D1/D2 sequence revealed that they were conspecific and most closely related to Zygosaccharomyces mellis.Based on the ITS sequence,the new species was clustered with the type"and clearly distinguished from the type!.Sequence analysis of combined ITS-26S rDNA D1/D2 showed similar results.The occurrence of these two types,with a divergence of more than 1%in their sequences,and low DNA relatedness among them suggested that members of the typeβcan be regarded as separate species.An analysis of the morphological and physiological characteristics was performed.Ascospore formation was observed on acetate agar and Gorodkowa agar.The new Zygosaccharomyces species differed physiologically from Z.mellis in 4 assimilation tests.This data supports the hypothesis that the new species,Zygosaccharomyces siamensis,is a novel ascosporogenous yeast.The type strain is JCM 16825T(=CBS 12273T)and a description is given here.
文摘Camel milk is traditionally considered to have medicinal characteristics that it has potential health benefits and could help to treat several illnesses. Particularly, it is closest to human breast milk and has high levels of nutrients and bioactive components. The aim of this study was to explore the antioxidant peptides derived from protein fractions of camel milk. Camel milk proteins(CMP) were fractionated into camel casein protein(CCP) and camel whey protein(CWP), which were hydrolyzed with pepsin to produce peptic digests P-CCP and P-CWP, respectively. RP-HPLC was used for fractionation of the peptides from the P-CCP and P-CWP. The antioxidant activities were evaluated using superoxide anion generating system of xanthine oxidase(XOD)and 2,2-diphenyl-1-picrylhydrazyl(DPPH) scavenging assay. Active peptides were analyzed using matrixassisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF-MS) whereas a number of antioxidant peptides, with masses ranging from 913 to 2,951 Da, derived mainly from alpha-casein, lactophorin and lactoferrin, were identified. When yeast cells are used as a system for modeling mitochondrial disease, the peptides in caseins and whey fractions significantly enhanced the tolerance of yeast cells against peroxide-induced oxidative stress. The results show that both caseins and whey proteins of camel milk possess bioactive peptides with significant radical-scavenging activities and thus herald a fascinating opportunity for their potential as nutraceuticals or therapeutic peptides for prevention and treatment of oxidative stress-associated diseases.
