Two brown-rot wood decay fungi, Fomitopsis pinicola and Meruliporia incrassata, and the white-rot species Phanerochaete chrysosporium were grown for 4 weeks in liquid culture at 0.35, 0.70, 1.05, and 5.00 mM calcium (Ca) and 1.35 and 2.70 mM magnesium (Mg) concentrations. Soluble and total oxalate levels were quantified using a revised ion-exchange HPLC protocol developed specifically for resolving oxalate and other organic acid anions from medium components. Total oxalate concentrations in brown-rot filtrate were not significantly different among treatments; however, soluble oxalate decreased significantly with increasing Ca concentration. Higher Mg concentrations increased soluble oxalate levels only slightly. There was a significant decrease in medium pH at 5.00 mM Ca for all species, as well as an apparent increase in decarboxylation activity in brown-rot fungi. Total and soluble oxalate levels in the white-rot cultures were generally below detection for all treatments. The results show a significant influence of Ca on soluble oxalate concentrations not seen previously in the brown-rot species Postia placenta.
Bibliographical noteFunding Information:
The authors would like to thank Dr. M. F. Stoner (CSU-Pomona) for his generosity in supplying field isolates of Meruliporia incras-sata, Dr. Barry Goodell for making his facilities available for this work, and Dr. A. Ostrofsky for her editorial assistance. This work has been supported by USDA grants 2001-34158-11113 and 2002-34158-12783 and the Maine Agricultural and Forestry Experiment Station. This is publication number 2720 of the MAFES.
- Oxalic acid