DIE groeibehoeftes van steenkoolgeassosieerde mikro-organismes.

Abstract

Because of the structure of coal, it cannot be biodegraded readily. Nature has not provided a method to process the carbon in coal molecules. Coal is also highly insoluble in water and many organic solvents , except under extreme circumstances. Current chemical processes in coal conversion are very costly and for this reason it is important to investigate alternative routes such as microbial liquefacti on or disintegration of coal. Certain Pseudomonas species are capable of partly degradi ng bituminous coal and, at the same time , converting it to water soluble brown substances and releasing surfactants in the medium. Large quantities of coal in South Africa became very expensive to mine utilizing conventional technology. Coal supplies 85% of South Africa's energy requirements at the moment and therefore methods to improve extraction in coal mines, further development of coal conversion technologies and energy conservation , should be improved. Biological treatment follows the following route: * organic or carbon portion - depolimerization - reduction of oxygen components - decarboxylation * removal of sulphur or nitrogen South African coal consists mainly of the macerals vitrinite, inertinite and exinite in different ratios, depending on the origin and specific layer formed . The material remaining on the grid after incineration, is mainly mineral matter. Coal bio-processing can be divided into two areas: • • coal purification coal conversion, -vi- The activities of micro-organisms are largely influenced by the chemical and physical conditions of their environment. When one understands the influence of the environment, the distribution of micro-organisms in nature can be understood and then the methods to control microbial activities can be developed. Any organism has, within its range of tolerance, an optimum for any given condition at which growth and multiplication will take place most rapidly. Tem perature is one of the most important environmental factors influencing growth and survival of organisms. Both the optimal growth temperature and the range of temperatures that an organism can withstand, will determine whether that organism will be present as well as its role in the ecosystem. Not only does pH influence thermal killing but it also plays an important role in optimal growth of micro-organisms. Most micro-organisms prefer a neutral pH of 7,00, although so me exceptions prefer an acidic or alkaline medium for growth. The effect of oxygen on growth of micro-organisms is clearly evident from the observations that certain micro-organisms can grow only in the presence of, and others can grow only in the absence of oxygen. Occasionally additional nutrients are required when culturing bacteria artificially. Such nutrients are present in yeast extract which is a complex nutrient source, meaning that its exact composition is unknown. The aim of the present research was to determine the growth requirements of coal- associated micro-organisms. Through this investigation it should be possible to establish the influence of certain environmental parameters such as temperature, pH, oxygen and yeast extract, on selected isolates. -vii- The investigation was divided into four sections: The effect of temperature on the growth of selected isolates The effect of pH on the growth of selected isolates The effect of oxygen on the growth of selected isolates The effect of yeast extract on the growth of selected isolates. The following observations were made: The various isolates preferred different temperatures, pH's and concentrations of oxygen for growth. Research has shown that a yeast extract concentration of 0,2% was optimal for growth of all the isolates. Should authorities concerned decide to use micro-organisms for comminution of coal that is difficult to mine, the results of this research can be applied in practice.