No abstract

The laccase activities of Penicillium simplicissimum H5 during solid-state fermentation with rice straw were studied. Degradation of lignocellulose was also followed. Results showed that all supplemental carbon sources inhibited the laccase activity in different degrees, while suitable concentrations of supplemental nitrogen sources remarkably enhanced the laccase activity. The enhancement of activity by the ordinary laccase inducers 2, 2¢-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) and xylidine was not observed in this study. Lignocellulose degradation was improved when laccase activity was relatively low, suggesting a polymerizing function of laccase in lignin degradation by P. simplicissimum.

Pot experiments were carried out to study the effect of compost application amount on the distribution of copper in heavy metal contaminated soil. The results showed that the total Cu content reduced 11.54%, 11.60%, 22.02%, 25.27%, 7.08% and 3.65% after the amendment of 0, 20, 40, 60, 80, 100 g/kg compost to soil with Brassica juncea, respectively. The amount of water-soluble fraction had no correlation with the compost application amount. However, compost amendment decreased the proportion of Cu in the exchangeable and residual fractions, and increased the percentage of Cu in the carbonate bound, Fe-Mn oxide bound and organic-bound Cu. Furthermore, though the mobility factor of Cu decreased slightly only from 16.64% to 16.27-16.52% due to the addition of compost, the addition of compost to soil can immobilize the heavy metal through bound to organic matter and therefore, lowered their mobility and their phytotoxicity.

Pot experiments were performed to investigate the effect of compost amendment on the mobility of zinc through analysis of Zn fractions in heavy metal contaminated soil. The results showed that the total Zn concentration decreased 8.11%, 10.15%, 16.15%, 20.05%, 7.28% and 5.02% after the amendment of 0, 20, 40, 60, 80, 100 g/kg compost to soil and Brassica juncea harvest, respectively. Zn was mostly concentrated in the residual fraction and Fe-Mn oxides fraction in soil. The percentage of Zn in water-soluble fraction, organic fraction and residual fraction had no correlation with the amount of compost amendment. The percentage of Zn in the exchangeable fraction decreased and the percentage of Zn in Fe-Mn oxides fractions increased obviously. Furthermore, the mobility factor of Zn decreased significantly from 19.20% without compost amendment to 19.09%, 18.70%, 18.15%, 16.45% and 16.12% after the amendment of 0, 20, 40, 60, 80, 100 g/kg compost to soil, the compost amendment could lowered the mobility and phytotoxicity of zinc through bound to Fe-Mn oxides.