Division of Biology, Faculty of Science, University of Zagreb
Abstract
Betanin belongs to a large family of betacyanin pigments, betalains, and in the food industry it is established as a powerful antioxidant and natural colorant. The main source of betanin is a red beet (Beta vulgaris L.), the yield depending on abiotic and biotic factors in the field. Sugar beet cells, transformed by a wild strain B6S3 of Agrobacterium tumefaciens, strongly produce betanin and could be a stable production source.With the aim of enhancing the yield, cell suspensions were initiated from friable calli. Biomass accumulation, betanin content and yield were monitored over 21 days in relation to changes of sucrose concentration, modifications of minerals in nutrient medium, and the usage of elicitors. Results showed that elevating sucrose levels from 3%to 4%, 5%, or 6%(w/v) in the original medium strongly induced biomass accumulation followed by an increase in betanin yield of up to 250%. Modification of minerals in the medium additionally increased betanin yield up to 20% in a few instances: 40 mg L–1 was recorded at day 10 with 5% and 6% of sucrose. The highest yield at 53 mg L–1 was reached at day 21 on 4% Suc, again with the modified medium. High sucrose concentrations positively affected betanin accumulation only during lag phase of the cell suspension, but afterwards the trend reversed. Calcium and yeast extract were used as abiotic and biotic elicitor, respectively, in the early exponential phase of subculture (day 7). Calcium ions (at 10 fold higher concentration than in the control) failed to increase betanin yield as well as yeast extract at 0.25% (w/v). Yeast extract at 1.25% provoked excretion of betanin at day 4, and cell necrosis at day 7 after elicitation. Taken together, in our system, sucrose affected betanin yield more strongly than medium modifications or elicitors. Yeast extract could be used for reverse- sequestration of betanin where the cells can be used over an extended period
