Ecological Aspects of the Biodegradation of Town Waste

Abstract

Investigations concerning the microbiology of the composting of town waste were carried out and these indicated that refuse, even on entry into the disposal system, is a rich source of micro-organisms. The myco-flora consisting of ten species of thermophilic and thirty-three species of mesophilic fungi. The microbiological changes which occurred during the composting of refuse were studied. The population of thermophilic actinomycetes became dominant with Thermomonospora curvata being particularly prevalent. Chaetomium thermophile was the most frequently isolated thermophilic cellulolytic fungus. The completion of these investigations coincided with the publication of a governmental report on refuse disposal which criticised and discredited the composting of refuse. Thus, the results of the ecological research completed at this stage were applied to the biodegradation of the main component of domestic refuse which is cellulose. A screening programme revealed that thermophilic fungi, generally have a much faster growth rate than mesophilic fungi. In shake-flask cultures with suspensions of ball-milled newsprint Chaetomium thermophile var dissitum and a variety of Sporotrichum thermophile combined the greatest degrees of substrate degradation with fungal protein synthesis. Two processes of fermentation of newsprint by thermophilic fungi were developed at the laboratory scale for the production of an animal feedstuff. Using a system of submerged fermentation it was found that two species were capable of utilising nearly all the available substrate indicating that they could be lignolytic as well as cellulolytic. A novel technique of solid substrate fermentation was developed using the ecological principle of competitive substrate colonisation as a means of obtaining the growth of the desired organism; instead of substrate sterilisation. Feeding trials demonstrated that the product of such a process is not acutely toxic and is of nutritional benefit.