Characteristics and Mechanisms of Biosolubilization of Rock Phosphate by Aspergillus japonicus

Abstract

Rock phosphate (RP) is traditionally solubilized by chemical process causing high cost and environmental pollution. To reduce process cost and protect environment, RP solubilization by Aspergillus japonicus was studied and its mechanisms were discussed. Results show that A. japonicus could effectively solubilize RP in NBRIP medium. RP solubilization by A. japonicus included direct and indirect actions of the strain on RP. Cells of A. japonicus attached rapidly to RP surface and the RP surface was seriously corroded by the strain. A. japonicus excreted multiple organic acids, and followed by a significant increase of titratable acidity and decrease of pH in the culture. A positive correlation between content of soluble phosphate and quantity of titratable acidity but a negative correlation between content of soluble phosphate and pH were observed. Results of abiotic solubilization of RP using organic and inorganic acids indicated that the release of soluble phosphate was significantly lower than that of inoculated with A. japonicus. Higher release of soluble phosphate and pH reduction achieved when using ammonium nitrogen rather than nitrate nitrogen.

A sustainable and effective bioprocessing approach for improvement of acid phosphatase production and rock phosphate solubilization by Bacillus haynesii strain ACP1

“…These documented findings have emphasized the predominance of lactic acid production among different species of microorganisms. It was shown that A. japonicas ' solubilization of RP resulted in the highest amount of gluconic acid production among other organic acids, as reported by Xiao et al 20 , which contradicts the present findings.…”

“…Researchers have a common assumption that the best medium chosen from shake flask data will be the best medium in a large-scale stirred tank 20 . In the current investigation, the production of extracellular ACP was monitored throughout the growth of B. haynesii strain ACP1 on an optimized medium in a shake-flask under standard cultivation conditions to find out what relationship there is between the culture's specific growth rate and the rate of ACP production using a cell growth kinetics strategies.…”

Screening of high-efficiency potassium-dissolving strains and optimization of the potassium-dissolving process

“…In the S3 SEM image, the mineral surface was covered with a film and pits following eight days of microbial erosion. It was speculated that the film may be metabolites of the microorganisms, with the mineral surface then destroyed by the metabolites, resulting in pits of different sizes on the surface (Xiao et al, 2018). After 10 days, this phenomenon was more obvious, and there were even potholes on the mineral surface.…”

“…Potassium in plants mainly exists in the cell fluid as free k+, which promotes the growth metabolism of the plant. At the same time, it is an essential element in many chemical reactions in plants, not only activating various enzymes to accelerate the metabolic rate, but also promoting the absorption and balance of other elements (Xiao et al, 2018). It can enhance the drought resistance, cold resistance, and stress resistance of plants by regulating the water content of cells.…”