Influence of nitrogen source NH4 Cl concentration on curdlan production in Alcaligenes faecalis / 生物工程学报

The effect of initial ammonium chloride level on production of curdlan in Alcaligenesfaecalis was investigated. It was found that ammonium chloride was the limiting substrate for cell growth during the batch fermentation process. However, the cell growth and curdlan production could not be enhanced by solely increasing the initial ammonium chloride level. The pH drop in the broth due to the consumption of ammonium chloride also effected the cell growth and curdlan production. By simultaneously increasing the initial ammonium chloride concentration and implementing an optimal pH control strategy, which is to control pH at 7.0 in the growth phase, and then shift to 5.6 in the production phase, the biomass and curdlan production in batch fermentation were increased markedly. If the initial ammonium chloride concentration was increased from 1.1 g/L to 3.6 g/L, biomass concentration of 7.2 g/L was obtained, and the final curdlan concentration reached 30.5 g/L, which was 51.7% higher than that of the former case. As the cell growth was improved due to the increase of the initial ammonium chloride concentration, the agitation speed and aeration rates must be enhanced to suit the higher oxygen uptake requirement. However, as curdlan molecules is subject to the structural breakage due to the high shear stress at higher agitation speed, an overall optimal condition for both productivity and quality of curdlan should be considered comprehensively.

Influence of pH control on the production of curdlan by Alcaligenes faecalis strain / 生物工程学报

A two-stage pH control method was employed in batch fermentation of curdlan by Alcaligenes faecalis WX-C12 where cell-growth stage was constantly controlled at pH 7.0 and stationary stage was controlled at a constant pH as well. The influence of pH control on the curdlan production was investigated. The optimal pH control of batch process for curdlan production was obtained when cell-growth stage was controlled at pH 7.0 and stationary stage was constantly controlled at pH 5.6. Production and productivity of curdlan, QP and YP/S reached 28.19 g/L, 291 mg/(L.h), 132.27 mg/(L.h.g) and 0.659, an improvement of 20.4%, 38.1%, 38.1% and 29.5% compared to a pH uncontrolled operation respectively.

A rapid Screening Procedure for Identification of Succinate Producing Anaerobic Strains / 微生物学通报

In order to obtain an efficient screening procedure for identification of succinate producing anaerobic strains,a semi-quantitative paper chromatography method was developed. Lactic acid and acetic acid were identified as the main byproducts in the process of succinate production by the high performance liquid chromatography (HPLC).Succinic acid was completely separated from the byproducts of lactic acid and acetic acid in the same broth developed by paper chromatography.The content of succinic acid was calculated by a semi-quantitative method.The results showed that paper chromatography was a simple and cost effective method that could be utilized to screen anaerobic strains producing succinic acid.