A study of possibility of expression of an alternasucrase gene in sugar beet to produce alternan biopolymer

Lactic acid bacteria (LAB) synthesize valuable industrial and pharmaceutical important biopolymers, such as Alternan, by expressing glycosyltransferase enzymes by utilizing extracellular sucrose. In this study, due to the importance of such versatile biopolymers in the industry and medicine, a gene encoding an Altranansucrase (Asr) was introduced to sugar beet plants.
 

A gene encoding the Asr gene was isolated from Leuconostoc mesenteroides bacterium and introduced to sugar beet plants by using Agrobacterium-mediated transformation. Molecular techniques were used to analyse transgenic plants and sugar content of sugar beet lines.
 

Out of 131 transformed explants, only three transgenic plants were produced, showing a transformation efficiency of 2.3%. The Asr gene integration in transgenic plants genome and expression were confirmed by specific PCR and semi-quantitative RT-PCR analysis, respectively. Sugar analysis of sugar beet transgenic plants showed that control plants with a 19.6% brix value (Sucrose) had more sucrose than transgenic plants with an average brix value of 14.4%. Brix in transgenic plants was lower than that of control plants. The amount of sugar (sucrose) in the transgenic asr-expressing plants reduced by 36.1% relative to the untransformed control plants.
 

The results of this study showed that Altrenansucrase can convert substantial amount of sugar beet sucrose into Alternan biopolymer, producing 36.6 mg/g FW alternan biopolymer with pharmaceutical and industrial applications.