Light-Dependent Betanin Production by Transformed Cells of Sugar Beet

Abstract

The objective of this work is to transform sugar beet (Beta vulgaris L. var. altissima) cells using Agrobacterium tumefaciens, a wild octopine strain B6S3, and to study metabolic changes associated with the transformation. From the primary tumours on leaf fragments, two tumour lines were established: one pale green and the other red-violet in colour. The red-violet pigment was identified by means of high-performance liquid chromatography as betanin. Betanin production is strongly light-dependent. To enhance the betanin yield, nutrient media with different carbohydrates like sucrose, a combination of glucose and fructose, or only glucose or only fructose were tested. The selection of carbohydrate affected betanin production and yield. It was observed that the production of betanin per g of dry mass was 20–40 % higher on simple carbohydrates, especially fructose, than on sucrose or the combination of glucose and fructose. However, due to higher biomass production on the medium with sucrose, the highest total yield of betanin was obtained in the presence of sucrose. The most suitable time for possible betanin extraction was between days 7 and 14 for tissue grown on sucrose. The tumour line seems to be promising as an alternative source of betanin as well as a model to study sugar-regulated genes involved in tissue morphology control.

Keywords

• Agrobacterium tumefaciens
• betacyanins
• carbohydrates
• in vitro tissue culture
• pigment
• secondary metabolites