Abstract
Thick juice (also regarded as syrup) is an intermediate product of sugar processing. It is cheaper than processed sugar and is mainly composed of sucrose. Sucrose is a preferred carbon source of Corynebacterium glutamicum, a workhorse of biotechnology used for million-ton-scale amino acid production. Here, it is shown for C. glutamicum that sugar beet thick juice led to higher growth rates and faster carbon source consumption than pure sucrose. Comparative DNA microarray analysis revealed differential expression of genes for butyrate and citrate catabolism and of NAD and biotin biosynthesis suggesting provision of these compounds by the thick juice. Thick juice was also shown to be superior to sucrose in production of the amino acids L-lysine, L-glutamate and L-arginine as well as of the diamine putrescine since higher volumetric productivities than with pure sucrose could be achieved. Taken together, sugar beet thick juice was shown to be a carbon source for growth and amino acid and diamine production of C. glutamicum superior to pure sucrose.
Highlights
With resources of fossil oil becoming limiting, biotechnological production is getting more and more attractive [1,2]
C. glutamicum WT which is able to utilize sucrose as sole carbon source via PTSS was used for growth experiments with thick juice
The sucrose concentration in the thick juice used was determined by HPLC as 642 g l-1
Summary
With resources of fossil oil becoming limiting, biotechnological production is getting more and more attractive [1,2]. One prospect is the use of thick juice, an intermediate product from sugar industry. While production of table sugar involves many steps starting with e.g. sugar beet or sugar cane and ending in white crystalline sugar. First sugar beet is washed thoroughly and cut into chips. Out of these chips a crude juice is extracted by hot water treatment. This crude juice contains about 150g l-1 sugar as well as several contaminants. These contaminants are removed by filtration resulting in light yellow colored thin juice. In order to get white crystalline sugar further concentration and cleaning steps like crystallization and centrifugation are required [3]. By using thick juice instead of fully processed sugar these steps are saved and thereby the associated costs
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