New potential application of kitchen refuse, succinic acid fermentation by Actinobacillus succinogenes ATCC 55618 to produce raw material of poly (butylene succinate) (PBS) was studied in this work. Preparation of kitchen refuse as media for succinic acid fermentation by A. succinogenes has been established. Succinic acid production and growth of A. succinogenes using kitchen refuse as substrate were significantly affected by additional nitrogen source and external gas composition The optimal kitchen refuse medium for maximal succinic acid production was 4% (w/v) glucose and 0.2% (w/v) yeast extract, biotin which support enzyme (Phosphoenolpyruvate carboxykinase) reaction in succinic acid fermentation was not essential. At optimal media and external CO2 supply, the highest succinic acid production was 68.3±0.7% (w/w) (based on glucose consumption) in flask reaction size with shaking rate of 65 rpm at 39°C, after 48 h. Succinic acid production with 68.5% (w/w) and 30.4 g/L of final concentration, resulted in productivity with 0.6 g/L/h were obtained when conducted in 1-L of bioreactor (Under controlled pH at 6.5 by 5 M NaOH, agitation speed of 100 rpm, a CO2 gas sparge rate of 1.0 vvm and at 39°C) . Kitchen refuse utilization for succinic acid by A. succinogenes suggested a promising practical way to produce substrate for biodegradable plastic synthesis.
A salting-out precipitation of sodium succinate was investigated by adding various predetermined amount of methanol or ethanol as an antisolvent to model solutions containing 5-25wt% of the sodium succinate and sodium succinate solutions (KRFBs) which are concentrated from kitchen-refuse fermentation broth. In case of KRFBs, the powder recovered was refined by sequential purifications with 1.5 and 2.0 mass ratio of ethanol/water (EtOH/H2O), respectively. Sodium succinate purity and impurities such as sodium salts of by-product organic acids, sugar, and protein in the powder derived from each step are evaluated. Ethanol as an antisolvent shows higher and more stable succinate recovery rate than methanol in both model solution and KRFBs. Over 95% of succinate recovery rate was obtained from each KRFB at more than 1.5 EtOH/H2O mass ratios. A protein, a major impurity after a recovery step, was dramatically removed by the first purification. Sodium salts of by-product organic acids almost remained in EtOH/H2O solution and were not detected in the powder after purification steps. More than 96wt% of sodium succinate purities were achieved from individual KRFB by salting-out precipitation using antisolvent, ethanol.
The discoloration of L-ascorbic acid (vitamin C) powders with a water content of 1 to 10% (w/w) during storage at a temperature of 60 to 90°C was investigated by monitoring the absorbance of L -ascorbic acid solutions at 360, 450 and 500 nm. The discoloration reaction of the L-ascorbic acid powders was expressed by the modified Weibull equation under any condition. The rate constant, the shape constant and the maximum absorbance were estimated based on the equation. The temperature dependence of the rate constant was expressed by the Arrhenius equation under every storage condition, and the values of the activation energy and frequency factor increased with the increase in the water content. Although the shape constant depended on the wavelength at which the discoloration was observed, it was independent of the temperature. The maximum absorbance at every wavelength was expressed as functions of the water content of L-ascorbic acid powders and the storage temperature. These results enable us to estimate the discoloration of L-ascorbic acid powders under any condition, while the water content and the temperature would be limited in the ranges of 0 to 10% (w/w) and 60 to 90°C, respectively.