Title A study of P release from Fe-P and Ca-P via the organic acids secreted by Aspergillus niger
Author Da Tian1,2†*, Liyan Wang1,2†, Jun Hu1,2, Liangliang Zhang1,2, Ningning Zhou1,2, Jingjing Xia1,2, Meiyue Xu1,2, Kianpoor Kalkhajeh Yusef1,2, Shimei Wang3,4, Zhen Li3,4, and Hongjian Gao1,2*
Address 1Anhui Province Key Laboratory of Farmland Conservation and Pollution Prevention, School of Resources and Environment, Anhui Agricultural University, Hefei 230036, P. R. China, 2Research Centre of Phosphorus Efficient Utilization and Water Environment Protection along the Yangtze River Economic Belt, Anhui Agricultural University, Hefei 230036, P. R. China, 3College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, P. R. China, 4Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Nanjing Agricultural University, Nanjing 210095, P. R. China
Bibliography Journal of Microbiology, 59(9),819-826, 2021,
DOI 10.1007/s12275-021-1178-5
Key Words Aspergillus niger, insoluble phosphates, organic acids, phosphorus release, TCA cycle
Abstract Phosphate solubilizing fungi (PSF) have been widely applied to dissolve insoluble phosphates (IPs). However, the PSF usually demonstrates a different phosphate solubilizing capacity for various IPs. This study explored the mechanisms of Aspergillus niger for the dissolution of ferric phosphate (FePO4, Fe-P), and tricalcium phosphate (Ca3[PO4]2, Ca-P) regarding the tricarboxylic acid (TCA) cycle. Aspergillus niger has higher phosphorus (P) content released from Ca-P, reached the maximum value of 861 mg/L after seven days of incubation, compared with the 169 mg/L from Fe-P. Oxalic acid promoted the release of P from Ca-P through the formation of calcium oxalate. The presence of Fe-P can stimulate A. niger to secrete large amounts of citric acid, confirmed by the enhancement of citrate synthase (CS) activity. However, citric acid only promotes 0.5% of P released from Fe-P. Meanwhile, although oxalic acid still dominates the release of P from Fe-P, its abundance was significantly declined. In contrast, oxalic acid also shows a higher P release ratio in Ca-P than citric acid, i.e., 36% vs. 22%. This study points to the future usage of A. niger to dissolve IPs in soil required to enhance oxalic acid secretion.