چكيده به لاتين
Study of soil bioremediation with special emphasis on the solid phase is of great importance. But due to complexity and the length of process time, the process has been less considered. Although ability of wood-decay fungi in biodegradation of aromatic hydrocarbons relying on their ligninolytic enzymes has been approved, mycoremediation of aliphatics has been the subject of few articles. In this study, in order to investigate the ability of wood-decay fungi to biodegrade n-hexadecane as the model pollutant, some fungi species were isolated from Guilan forests. Azo dyes decolorization experiments were carried out in liquid phase and bromophenol blue agar culture media to examine the biodegradation abilities of 19 isolated fungi. Four wood-decay fungi selected by the preliminary tests were chosen for n-hexadecane biodegradation in the solid phase soil. The system used consisted of 28 small columns with the length to diameter ratio of 4 and containing 35g of soil for each column (hexadecane initial concentration 25000 mg/kg soil) with every 24h intermittent aeration at flow rate 0.25l/min. Four fungi were inoculated into soil under three different conditions: free cells, immobilized cells on sawdust and mixture of free cells and sawdust as a co-substrate. At the end of 120 days of the process, the highest biodegradation of 99.88% were observed for free cells of fungus number 15. The highest removal percentages were obtained about 94.5% by immobilized cells and 90% by mixture of free cells and sawdust for fungus number 4. In general, in the four fungi studied, adding sawdust (in free and immobilized cells) reduced biodegradation of contaminants or had no effect on it. This confirms that the biological removal of linear hydrocarbons is non-ligninolytic. In fact, fungi species produce laccase, lignin and manganese peroxidase enzymes in presence of sawdust, so they would rather rot wood and decompose lignin, resulting in less consumption of hexadecane as carbon source.
