Modelling of ergosterol production by S. cerevisiae in presence of n-dodecane as oxygen-vector

The previous studies on ergosterol production by Saccharomyces cerevisiae in presence of n-dodecane as oxygen-vector have been continued by mathematical modelling the fermentation process. In this purpose, the most efficient fermentation regime has been considered, namely fed-batch fermentation, and was based on the influences of hydrocarbon volumetric fraction, biomass concentration, and aeration rate on the ergosterol content inside the yeast cells. The model describing the fermentation process has been established by means of the statistical analysis, using a factorial experiment of second order. The considered variables control the ergosterol production in a 94.4% extent, the biomass concentration exhibiting the most important influence.

Enhancement of L-amino Acid Oxidase Production by Bacillus Subtilis HLZ-68 With Oxygen-vector and Asymmetric Degradation of DL Arginine to D-arginine

The Bacillus subtilis HLZ-68 independently screened by our laboratory can produce L-amino acid oxidase (L-AAO), and DL-arginine can be degraded asymmetrically by suspending the wet bacteria in the degradation liquid. By adding oxygen-vectors to the fermentation medium, the collected amount of wet bacteria can be increased. Taking n-dodecane, n-hexadecane, oleic acid, paraffin, and n-hexane as oxygen-vectors, the optimal oxygen-vector oleic acid was 1.2% (v/v). The weight of wet cells increased by 66.83% compared with before, and the activity of L-AAO in fermentation broth increased by 38.88% compared with before. The standard sample DL-arginine was derivatized by phenyl isothiocyanate, and then subjected to high performance liquid chromatography(HPLC), and the obtained peak area and arginine content were used as standard curves to measure the DL-arginine. The content of D-arginine and L-arginine in the initial degradation solution was 50% each, and the bacterial cells are added to the initial degradation solution of DL-arginine. After 21 hours of reaction, L-arginine was completely Degraded, remaining 47% of D-arginine.D-alanine was easily extracted from the reaction solution using cation-exchange resin,after centrifugation, decolorization, concentration and vacuum drying, and the chemical and optical purity of the extracted d-alanine was 92.68 and 97.46%, respectively.

Enhancement of L-amino Acid Oxidase Production by Bacillus Subtilis H-8 With Oxygen-vector and Asymmetric Degradation of DL Arginine to D-arginine

The Bacillus subtilis H-8 independently screened by our laboratory can produce L-amino acid oxidase (L-AAO), and DL-arginine can be degraded asymmetrically by suspending the wet bacteria in the degradation liquid. By adding oxygen-vectors to the fermentation medium, the collected amount of wet bacteria can be increased. Taking n-dodecane, n-hexadecane, oleic acid, paraffin, and n-hexane as oxygen-vectors, the optimal oxygen-vector oleic acid was 1.2% (v/v). The weight of wet cells increased by 66.83% compared with before, and the activity of L-AAO in fermentation broth increased by 38.88% compared with before. The standard sample DL-arginine was derivatized by phenyl isothiocyanate, and then subjected to high performance liquid chromatography(HPLC), and the obtained peak area and arginine content were used as standard curves to measure the DL-arginine. The content of D-arginine and L-arginine in the initial degradation solution was 50% each, and the bacterial cells are added to the initial degradation solution of DL-arginine. After 21 hours of reaction, L-arginine was completely Degraded, remaining 47% of D-arginine.D-alanine was easily extracted from the reaction solution using cation-exchange resin,after centrifugation, decolorization, concentration and vacuum drying, and the chemical and optical purity of the extracted d-alanine was 92.68 and 97.46%, respectively.