Study On The Suillus Oxalic Acid Secretion And Its Metabolic Pathway

Suillus luteu is a symbiotic ectomycorrhizal fungi with Pinaceae, it can activate the insoluble nutrient elements in soil by secreting organic acids. Suillus luteus can secrete oxalic acid in the liquid medium after a certain time, and the secretion of oxalate acid is gradually increase with the pH increase in the pH range from3.0to6.5. However, the metabolic mechanism of oxalic acid and production pathway is not clear. In order to investigate the metabolic pathway of the fungi oxalic acid, the secretion of oxalate acid by Suillus luteus in the different nutritional conditions and different oxalate metabolism precursors has been studied, and the enzyme activity related with oxalate metabolism has been measured. The results show that, the effects of different nitrogen sources on Suillus luteu oxalic acid secretion are different, the oxalate acid secretion in ammonium nitrate is higher than in ammonium tartrate at the pH (4.0,4.5,5.0), but the result is reversed in the higher pH (6.0,6.5); the optimum phosphorus concentration of Suillus luteu mycelial growth is0.002mol/L, no or low-level phosphorous can significantly promote oxalic acid secretion, but high-level phosphorous will inhibit the secretion of oxalic acid. The activity of glycolate oxidase and ascorbate peroxidase are not detected in the Suillus luteu, but the activity of isocitrate lyase and malate synthase can be detected, and the highest activity of isocitrate lyase and malate synthase are at about pH5.0when Suillus luteu are cultured in the different pH.