Effect of environmental parameters on the efficiency of biodegradation of basalt rock by fungi

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Abstract
The biodegradation of an aluminum‐bearing (basalt) rock by Penicillium simplicissimum has been investigated. This organism grows on a sugar substrate and releases organic acid compounds. These acids interact with the mineral matter and cause their partial decomposition. The dissolved metals are then complexed by the excess organic acids. The activity of the fungi was found to be optimum at an initial pH 7 and in the presence of 5% (w/v) substrate concentration. In 30 days of leaching almost 20% of the aluminum in the rock was solubilized and the pH was decreased from 7 to less than 3.5 in the inoculated flasks. The controls showed less than 1% of the aluminum solubilized and the final pH dropped to only 6.8. A surface characterization study performed by scanning electron microscopy indicated that the specific mineralogical phases containing aluminum and iron within this host rock were preferentially corroded. The mineral phases containing olivine and plagioclase were found to be least resistant, while phases containing titanium were most resistant to the acids released by the fungi.