Abstract
ABSTRACT In the process of L-glutamic acid fermentation, there are proteins that cannot be decomposed and utilized by bacteria and that secreted by bacteria at the same time, which cause problems such as increased foam production in the fermentation broth that lowers the dissolved oxygen, which makes the total fermentation efficiency low. Therefore, these proteins can be decomposed by adding proteases in the fermentation broth, and it is found that the best results are obtained by adding 0.5 g/L of trypsin. Proteins can be used by bacteria after being decomposed as well. The final L-glutamic acid production in our research was 177.0 g/L, which is 14.9% more than the control fermentation (154.0 g/L). Similarly, the glucose conversion rate was 68.3%, which is an increase of 4.0% as compared to the control fermentation (65.6%).
Highlights
The production of L-glutamic acid has undergone substantial changes over time
Since corn syrup, soybean meal hydrolyzate were used and seed liquid contain more proteins, the fermentation broth contains a considerable amount of proteins at the time of initial fermentation
The fermentation conditions were not the optimal viability conditions for the protease, by adding trypsin, the hydrolysis of the total proteins in the fermentation broth was as high as about the 30.0%. These proteins were hydrolyzed into various amino acids, peptides and small molecular weight proteins that are used by the cells to promote the growth and metabolism of the cells
Summary
The production of L-glutamic acid has undergone substantial changes over time. A transformation from the hydrolysis and enzymatic hydrolysis methods to the fermentation, which has greatly improved the acid production, reduced the production cost, making the L-glutamic acid one of the widely used bulk amino acids [1; 2]. For L-glutamic acid production, the use of nutrient-rich and inexpensive fermentation media is one of the main strategies for reducing production costs [6]. The main sources of L-glutamic acid fermentation nutrients include corn syrup, soybean meal hydrolyzate. The corn syrup and the soybean meal hydrolyzate contain a variety of small molecular weight proteins, peptides, and a variety of amino acids. They contain a wide range of vitamins and trace elements, which are indispensable for the growth of the cells [7,8]. These substances are used as nitrogen sources and cofactors for
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