[Objectives] The fermentation conditions of Candida tropicalis 1798-pxa1 were optimized to further improve its yield of long-chain dibasic acids. [Methods] The strains used in the study were C. tropicalis 1798, C. tro...[Objectives] The fermentation conditions of Candida tropicalis 1798-pxa1 were optimized to further improve its yield of long-chain dibasic acids. [Methods] The strains used in the study were C. tropicalis 1798, C. tropicalis 1798-pxa1 and C. tropicalis 1798-pxa1 p2. First, through single factor experiments, the activated three fungi were cultured in different carbon sources, and the absorbance was measured every 2 h. The growth curve was drawn by software, and finally the most suitable substance for the substrate was selected, i.e., dodecane. Then, the composition of the fermentation medium and the fermentation process parameters were determined through the PB experiment of the single-deletion C. tropicalis 1798-pxa1. [Results] The experiment determined the important components affecting the synthesis of long-chain dibasic acids, namely(NH_4)_2SO_4, NaCl and dodecane. After optimization of the culture conditions, the yield of long-chain dibasic acids of C. tropicalis 1798-pxa1 increased from 5.6 to 10.1 g/L. [Conclusions] The scheme has been verified to be capable of greatly increasing the yield of the corresponding long-chain dibasic acids of the C. tropicalis engineering strain.展开更多
The new theoretical method for the accurate determination of acidity of dilute solutions of weak multibasic organic acids (which are widely used in medicine, pharmacology, various branches of industry and participate ...The new theoretical method for the accurate determination of acidity of dilute solutions of weak multibasic organic acids (which are widely used in medicine, pharmacology, various branches of industry and participate in important biological processes in living organisms) is suggested. The concepts of the contributions of the separate dissociation steps to the [H+] value, xm, are used for an analysis of complex equilibria of the processes of dissociation of these acids. The cases of weak dibasic and tribasic organic acids with the “overlapping” dissociation equilibria and a general case of weak multibasic acids, HnA, are considered. From the conditions of equality of the concentrations of various ionized and non-ionized forms in the dilute solutions of weak multibasic organic acids the areas of dominance of these forms in connection with the corresponding xm values are formulated.展开更多
文摘[Objectives] The fermentation conditions of Candida tropicalis 1798-pxa1 were optimized to further improve its yield of long-chain dibasic acids. [Methods] The strains used in the study were C. tropicalis 1798, C. tropicalis 1798-pxa1 and C. tropicalis 1798-pxa1 p2. First, through single factor experiments, the activated three fungi were cultured in different carbon sources, and the absorbance was measured every 2 h. The growth curve was drawn by software, and finally the most suitable substance for the substrate was selected, i.e., dodecane. Then, the composition of the fermentation medium and the fermentation process parameters were determined through the PB experiment of the single-deletion C. tropicalis 1798-pxa1. [Results] The experiment determined the important components affecting the synthesis of long-chain dibasic acids, namely(NH_4)_2SO_4, NaCl and dodecane. After optimization of the culture conditions, the yield of long-chain dibasic acids of C. tropicalis 1798-pxa1 increased from 5.6 to 10.1 g/L. [Conclusions] The scheme has been verified to be capable of greatly increasing the yield of the corresponding long-chain dibasic acids of the C. tropicalis engineering strain.
文摘The new theoretical method for the accurate determination of acidity of dilute solutions of weak multibasic organic acids (which are widely used in medicine, pharmacology, various branches of industry and participate in important biological processes in living organisms) is suggested. The concepts of the contributions of the separate dissociation steps to the [H+] value, xm, are used for an analysis of complex equilibria of the processes of dissociation of these acids. The cases of weak dibasic and tribasic organic acids with the “overlapping” dissociation equilibria and a general case of weak multibasic acids, HnA, are considered. From the conditions of equality of the concentrations of various ionized and non-ionized forms in the dilute solutions of weak multibasic organic acids the areas of dominance of these forms in connection with the corresponding xm values are formulated.
