Forty-three samples of kurut, a kind of traditional naturally-fermented yak milk, were collected in Qinghai, China. One hundred and forty-eight lactic acid bacterial (LAB) strains were isolated and identified from the kurut samples according to phenotypic characterization and 16S rRNA gene sequence analysis. Among them, 52 isolates belonged to the Lactobacillus strains. Ninety-six isolates were resolved to coccoid LAB. The results showed that these isolates belonged to five genera and thirteen different species and subspecies. Moreover, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus were the predominant population in these samples. This paper systematically studied the composition of LAB in kurut, which may provide raw data for further study involving probiotics strain selection and starter culture design for industrialization production of traditional fermented milk in the future.
Biological transformation of Cr(VI) to Cr(III) by enzymatic reduction may provide a less costly and more environmentally friendly approach to remediation. In a previous report a Cr(VI) resistant actinomycete strain, Streptomyces sp. MC1, was able to reduce Cr(VI) present in a synthetic medium, soil extract and soil samples. This is the first time optimal conditions such as pH, temperature, growth phase and electron donor have been elucidated in vitro for Cr(VI) reduction by a streptomycete. Chromate reductase of Streptomyces sp. MC1 is a constitutive enzyme which was mainly associated with biomass and required NAD(P)H as an electron donor. It was active over a broad temperature (19-39ºC) and pH (5-8) range, and optimum conditions were 30ºC and pH 7. The enzyme was present in supernatant, pellet and cell free extract. Bioremediation with the enzyme was observed in non-compatible cell reproduction systems, conditions frequently found in contaminated environments.
Single-chamber microbial fuel cells (MFCs), inoculated with anaerobic sludge and continuously run with two kinds of organic wastewater influents, were systemically investigated. The diversity of microbes, determined by 16S rDNA analysis, was analyzed on three anodes under different conditions. One anode was in a closed circuit in synthetic wastewater containing glucose. The other two anodes, in open or closed circuits, were fed effluent from an anaerobic reactor treating starch wastewater. The chemical oxygen demand (COD) removal efficiency was about 70%, and the exported voltages were about 450 mV. The 16S rDNA molecular clones of microbes on anode surfaces showed significant changes in Eubacterial structure under different conditions. γ-Proteobacteria and the high G+C gram-positive groups were predominant in the synthetic wastewater, while ε-Proteobacteria predominated in the anaerobic reactor effluent. Known exoelectrogenic bacterial species composition also changed greatly depending on substrate. On the artificial substrate, 28% of the bacterial sequences were affiliated with Aeromonas, Pseudomonas, Geobacter, and Desulfobulbus. On the anaerobic effluent, only 6% were affiliated with Geobacter or Clostridium. Because only a few exoelectrogenic bacteria from MFCs have been directly isolated and studied, we compared the community structures of two bacterial anodes, in open and closed circuits, under the same substrate of anaerobic effluent in order to identify additional exoelectrogenic bacterial strains. Alcaligenes monasteriensis, Comamonas denitrificans, and Dechloromonas sp. were found to be potential exoelectrogenic bacteria worthy of further research.
Two strains of yeasts isolated in Thailand were found to represent a novel species of the genus Vanderwaltozyma. These strains are close to V. verrucispora but differ by 13 nucleotides (2.3%) in the D1/D2 domain of the LSU rRNA gene. This difference clearly suggests that the two strains represent a distinct species. It is described as Vanderwaltozyma tropicalis sp. nov. Vanderwaltozyma tropicalis is distinguished from V. verrucispora by the assimilation of trehalose, inability to grow in 0.1% cycloheximide and by higher maximum growth temperature.
A total of 4 strains (DR2-4, DW2-1, DS2-1 and DS3-1) of undescribed ascomycetous yeast, isolated from Nam Nao forest soil, were identified as a novel species in the genus Millerozyma. The D1/D2 sequences of the strains differed from the closely related species Millerozyma acaciae and Pichia koratensis by 1.2% (7 nucleotide substitutions) and 1.4% (8 nucleotide substitutions). Phenotypically, all the novel strains were identical, but differed from M. acaciae and P. koratensis by a variety of phenotypic characteristics. Based on phenotypic and phylogenetic data, these four yeast strains were assigned to a single novel species in the genus Millerozyma and the name Millerozyma phetchabunensis sp. nov. is proposed. In addition, we also propose the transfer of P. koratensis, which was placed in the Millerozyma clade based on the analysis of the D1/D2 and ITS sequences, to the genus Millerozyma as M. koratensis comb. nov.