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Microbial Community Succession during Composting of Biowaste as evaluated by Plating Techniques and Denaturing Gradient Gel Electrophoresis Analysis

SUMMARY:
Although several reports are available concerning the microbial community succession during composting of municipal solid waste, little is known about the microbial diversity, activity and evolution during composting of biowaste (vegetable, fruit and garden waste). In the present work we aimed at gaining a more complete picture of the microflora evolution during composting of biowaste in a pilot plant in Heraklio, Crete, from raw material to mature compost, with regard to abiotic factors, microbial activity and succession of functional and taxonomic groups.

Samples were taken from a typical windrow composting system during a 125- days processing period. The initial material was a mixture of food and garden waste, at a ratio of 1:1. Food waste was source separated. The succession of the microbial community was studied using a combination of traditional techniques with molecular ones (16S Ribosomal DNA Analysis). Temperature of the composting material, moisture and volatile solids content, C:N ratio, pH, O2 concentration and CH4, CO, and CO2 production were measured during the composting process. A standard procedure for sampling of the compost and selective substrates were used for the enumeration of the different groups of microorganisms (total bacteria, amylolytic, cellulolytic and proteolytic bacteria, enterobacteria, fungi and yeasts). Mesophilic and thermophilic microorganisms were incubated at 30°C and 55°C respectively. Furthermore, denaturating gradient gel electrophoresis (DGGE) analysis of PCR-amplified small subunit rDNA genes was applied to the samples. The compost temperature reached its maximum value of 67°C at the 25th day of the process. Escherichia coli was detected in the raw material and the following 5 samples, although the temperature had reached 67°C. However, after the 92nd day, the population of Escherichia coli declined below the detection limit. The total colliforms population decreased during the process, but was detectable until the end of the process. Many of the microorganisms examined decreased during the thermophilic phase of the composting, but increased again when the temperature begun to drop. In the DGGE profiles, several bands were detected and the dominating ones were sequenced. Nucleotic sequences in a successfully isolated band on the DGGE profile showed, through comparison to 16S rDNA genes using the BLAST algorythm, the highest similarity to Sphingobacterium faecium.

Copyright:	© European Compost Network ECN e.V.
Quelle:	Orbit 2006 (September 2006)
Seiten:	8
Preis:	€ 4,00
Autor:	Christina Chroni A. Kyriacou T. Manios M. Kotsou Dr. Katia Lasaridi
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