Ecological Studies of the Biodeterioration of a Model Cellulose Substrate by Fungi

Abstract

A technique has been described which successfully maintains a controlled microenvironmental condition on a cellulosic substrate by continuous perfusion with a predetermined nutrient solution. This technique has been used to study the effect of different ecological factors namely pH, temperature, nitrogen sources and glucose nutrition on the fungal colonization of a model cellulose substrate in the form of heat rolled polythene backed cellulose chromotography paper, buried in soil. Different successional patterns of fungi colonizing this substrate, have been elucidated and the role of " secondary sugar fungi" has also been elaborated. The extent of biodeterioration of the cellulosic substrate has been determined by its weight loss estimations. Maximum biodeterioration was recorded at 50°C. The role of thermophilic actinomycetes in the cellulose biodeterioration has been elucidated by using the perfusion technique for their selective isolation. Five species were identified and their cellulolytic ability was also determined. The relative cellulolytic ability of all the fungi isolated has been estimated by measuring the depth of clearing of the cellulose agar columns. The effect of pH, temperature, nitrogen sources and glucose nutrition on the relative cellulolytic ability has also been observed. An alteration of the perfusion technique has been described and used to study the effect of diffusible metabolites of cellulolytic fungi on their linear growth. The effect of non diffusible metabolites of these fungi on their cellulolytic ability has also been studied by growing them in mixed culture and then observing the clearing of the cellulose agar. There were very few cases of synergism as compared to widespread inhibition. The perfusion technique has also been used to study the germination and penetration of the spores of ten cellulolytic fungi through different thicknesses of fibreglass cloth. The mode of cellulase production and its diffusion was also analysed by estimating the weight loss of the different layers of a wad of five perfused cellulose strips, after inoculating the top strip. The perfusion technique has also been used as a test method for screening different biocides commonly used as textile preservatives. Its scope in detoxification studies has also been discussed.