Characterisation of Microbial Communities During Composting of Organic Wastes
Community level physiological profiles (CLPPs) tested with Biolog microplates were studied for a maturity sequence of compost from source-separate collected organic waste and prunings. The composts were 42, 120 and 240 days old. Traditional maturity param
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Introduction Composting is a term referring to the decomposition of organic materials by microorganisms under aerobic conditions, usually encompassing mesophilic and thermophilic phases. It is an environmentally sound way to reduce organic wastes and produce organic fertiliser or soil conditioner (Gajdos 1992). Although composting is a microbiological process, little is known about the microorganisms involved and their activities during the specific phases of the composting process. Several methods such as cultural and non-cultural techniques have been used for characterising the microorganisms during composting (Laine et aI. 1997; Klamer and Baath 1998; Tiquia and Tam 2000) Community level physiological profiling is a simple method to characterise microbial communities from environmental samples (Garland and Mills 1991; Zak et aI. 1994; Insam et aI. 1996; Guckert et aI. 1997; Ibekwe et aI. 1998; Choi et aI. 1999). Biolog microplates, such as the EcoPlate (Insam 1997) containing 31 different substrates as sole carbon sources (three replicates of each substrate in a 96-well microplate) can be directly inoculated with a mixed populations from sample extractions. The color formation from reduction of a tetrazolium dye in the Biolog microplates indicates the degradation of the specific C source. Changes in the patterns of carbon source utilisation assess the functional differences in the microbial communities. The aim of this study was to differentiate microbial communities during composting of source-separate collected organic waste by using CLPPs and to identify those substrates that contribute most to this differentiation.
1jnstitute of Microbiology, University ofInnsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
H. Insam, N. Riddech, S. Klammer (Eds.) Microbiology of Composting © Springer-Verlag Berlin Heidelberg 2002
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Material and Methods
Composting Site, Sampling and Sample Preparation
Samples were collected from the open-air windrow composting site at V6ls, Austria. The substrates were source-separate collected organic waste, amended with suitable amounts of bulking agents (wood chips, prunings). The windrows were turned two times a month, watering was not necessary. The samples (I kg) were taken at a depth of about 20 cm from three piles of different maturity. Each pile was sampled at three distinct locations. Samples were immediately sieved (2mm mesh) for analysis. The temperature at a depth of about 60 cm was recorded using a thermocouple (Sandberger, Austria). The moisture content was determined by drying at 105°C for 24 h. For pH determination, 1 g of compost was diluted with 10 ml of 1 M KCl solution and measured with a pH meter (Sentron, 2001 pH) (Forster 1995). Microbial Extraction
For the extraction, a modified procedure of Hopkins et aI. (1991) (Insam et aI., 2001) was used. Five g of sample was blended with 20 ml of 0.1% (w/v) sodium cholate solution, 8.5 g of cation exchange resin (Dowex 50 W x 8, 20-50 mesh, Sigma) and 30 glass beads. The suspension was shaken on a recipr
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