Screening Identification And Fermentation Characteristics Of A Strain For Producing Succinic Acid

Succinic acid is valued as one of the key platform chemicals as a raw material in broad applications. Succinic acid produced by various microorganisms can be used as a precursor of many industrially important chemicals in food, chemical and pharmaceutical industries. Till date, succinic acid is being commercially manufactured by chemical synthesis which is not only tedious and expensive but is also hazardous to environment which limits the use of succinic acid for the wide range of applications. Compared to traditional chemical synthesis, succinic acid production by fermentation has some benefits. Fermentation organism is the key part of the fermentation method. At present, many different microorganisms have been screened and studied for succinic acid production, that focusing on the use of several promising succinic acid producers including Actinobacillus succinogenes, Anaerobiospirillum succiniciproducens, Mannheimia succiniciproducens and recombinant Escherichia coli.In high selectivity enrichment culturing process and rapid screening procedure, succinic acid producers were isolated from soil. Morphology analysis, physiological and biochemical properties and phylogenetic analysis sequence indicated that the strain belonged to Enterobacter. Preliminary studies of growth and fermentation characteristics were carried. The main results were as following:1. This paper focused on the study of screening procedure for identification of Succinate producing strains. About 80 strains were gained from soil with the bromocresol green medium as the selective mark. Then 5 strains were selected at the following period with the TLC method by the appearance of the succinic acid spot in the plate. Five high yield strains were gained with the HPLC analysis method. The potential strain was the strain JLT9 and its yield of succinic acid was 6.01 g/L.2. The individual cell and clonies morphologic characteristics of the strain JLT9 were studied.According to the traditional morphological characters, physiological and biochemical properties,as well as chemical characteristics, they were preliminary identified to Enterobacter.To further the strain of JLT9,the genes of 16S rDNA were amplified in vitro and sequenced.Then a phylogenetic was constructed by comparing the sequenced with other 16S rDNA/RNAsequences in GenBank.The results indicated that the homology of JLT9 with AF395913.1 was 99%,and AF395913.1 is Enterobacter aerogenes,combined with analysis of the phyolgenetic tree and partial sequences of 16S rDNA, JLT9 was classified as AF395913.1.belonged to Enterobacter aerogenes.The result was as same as that of traditional classification before.3. The growing rule was confirmed by According to this growing curve,the results it was found that the logarithmic phase of JLT9 was 2-12 hours after it was cultured, then the strain of metabolic function active and cell concentration increased significantly; and stabilization phase after 12 hours later, as cell concentrations increases, the value-added rate gradually decreased, the cell has stopped increasing.As the same way to culture the strains by measuring the growth curve of JLT9, every 2 hours measured the pH of fermentation and the fermentation measured the volume of consumption NaOH standard solution were cosumed, drawing curves, we can see changes in pH value of the logarithmic growth phase in the cell is more significant, indicating Acid is produced mainly in the logarithmic growth phase; consumption of volume of NaOH standard solution in the early stage of fermentation, which produced more acid in the logarithmic growth phase. Fermentation broth by measuring the pH value and the volume of NaOH standard solution can be reached, the production of succinic acid is done in the logarithmic growth phase.