Studies on Some Growth Related Changes in Cultures of Aspergillus niger and Aspergillus Parasiticus Treated with Hexavalent Chromium andTannic Acid

摘要

The growth of A. niger and A. parasiticus in Vogel's medium treated with varying concentrations of chromate (5 - 25 mg/1) and tannic acid (250 - 1500 mg/1) was studied. Spores of the fungi were inoculated into batch reactors, containing 100 ml of thetreated media, and then grown on a rotary shaker (200 - 300 rpm) at pH 5.0 and temperature of 30 deg C for 96 - 168 hours. Significant (P < 0.001) decreases in biomass yield were observed with increasing Cr (VI) concentrations in cultures of both fungi.The biomass yields were significantly (P < 0.05 - 0.001) higher at tannic acid concentrations of 250, 500 and 750 mg/1 compared to values for the control organisms, with optimal yield obtained at 500 mg/1 for both A. niger and A. parasiticus, but concentrations 1250 and 1500 mg/1 were inhibitory to the two fungi. When cultured at the tannic acid concentration of 500 mg/1, which produced optimal biomass yield, increasing Cr (VI) concentrations (from 5-25 mg/1) caused significant (P < 0.001) decreases inbiomass. Increasing chromate concentrations also significantly (P < 0.001) impaired the uptake and/or utilisation of both glucose and tannic acid by the two fungi. The significance of these findings is discussed in relation to the potential of the two fungi as agents of bioremediation for tannin and chrome bearing industrial effluents.