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  • 1
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Composting relies on a complex network of bacteria and fungi to process crude organic material. Although it is known that these organisms drive dynamic changes in temperature and pH, little is known about the temporal dynamics of fungal populations during the rise to thermophilic conditions. This study employed F-ARISA (fungal-automated rRNA intergenic spacer analysis) and 18S rRNA gene cloning and sequencing to examine changes in community structure during this period. Sequencing of the 18S rRNA portion of cloned F-ARISA products revealed the presence of four distinct fungal genera including Backusella sp., Mucoraceae, Geotrichum sp. and the yeast Pichia sp. Based on the presence and absence of these ARISA operational taxonomic units (A-OTUs), we observed a shift in fungal community structure between 48 and 60 h. This change in community structure preceded a rise in pH and coincided with an increase in temperature. Clone libraries constructed using fungi-specific 18S rRNA primers contained sequences similar to several other fungal genera including Penicillium sp., Aspergillus sp., Hamigera sp., Neurospora sp. and the yeast Candida sp. While the fungal species richness was relatively low at any time point, the community structure was dynamic and paralleled changes in bacterial community structure.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The initial phase of composting is the most dynamic part of the process and is characterized by rapid increases in temperature, large swings in pH, and the degradation of simple organic compounds. DNA samples were taken from an active compost system to determine the microbial 16S rRNA gene sequences that were present during this phase. We observed two significant shifts in the composition of the microbial community, one between 12 and 24 h and the other between 60 and 72 h into the process using automated 16S–23S rRNA intergenic spacer amplification (ARISA). The 16S rRNA gene sequences adjoining the most common ARISA fragments at each time point were determined. We found that sequences related to lactic acid bacteria were most common during the first 60 h and Bacillus-type sequences were most common between 72 and 96 h. While the temperature increased steadily over the first 96 h, the pH dropped after 12 h and increased after 60 h correlating with the shift from Bacillus to lactic acid sequences and the later return to Bacillus-type sequences.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0006-3592
    Keywords: endocellulase ; exocellulase ; Thermomonospora fusca ; Trichoderma reesei ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The activities of six purified Thermomonospora fusca cellulases and Trichoderma reesei CBHI and CBHII were determined on filter paper, swollen cellulose, and CMC. A simple method to measure the soluble and insoluble reducing sugar products from the hydrolysis of filter paper was found to effectively distinguish between exocellulases and endocellulases. Endocellulases produced 34% to 50% insoluble reducing sugar and exocellulases produced less than 8% insoluble reducing sugar. The ability of a wide variety of mixtures of these cellulases to digest 5.2% of a filter paper disc in 16 h was measured quantitatively. The specific activities of the mixtures varied from 0.41 to 16.31 μmol cellobiose per minute per micromole enzyme. The degree of synergism ranged from 0.4 to 7.8. T. reesei CBHII and T. fusca E3 were found to be functionally equivalent in mixtures. The catalytic domains (cd) of T. fusca endocellulases E2 and E5 were purified and found to retain 93% and 100% of their CMC activity, respectively, but neither cd protein could digest filter paper to 5.2%. When E2cd and E5cd were substituted in synergistic mixtures for the native proteins, the mixtures containing E2cd retained 60%, and those containing E5cd retained 94% of the original activity. Addition of a β-glucosidase was found to double the activity of the best synergistic mixture. Addition of CBHI to T. fusca crude cellulase increased its activity on filter paper 1.7-fold. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 494-501 
    ISSN: 0006-3592
    Keywords: mixture optimization ; cellulase ; experimental design ; synergism ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A factorial experimental design approach was used to optimize mixtures of six cellulases (five Thermomonospora fusca cellulases and plus/minus Trichoderma reesei CBHI along with β-glucosidase) so as to maximize the glucose produced from filter paper. Optimized mixture A and mixture B produced glucose at 25 and 8.3 μmol glucose/μmol enzyme/min, respectively, which are 8 and 1.5 times higher than the sum of the activity of the individual cellulases. In both mixtures, the glucose yield depended on the ratio and the cellulases used. Most enzymes showed synergistic interactions that increased the glucose yield. The yield of glucose with the optimum mixtures depended on the total enzyme concentration. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 494-501, 1998.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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