Inductive effect produced by a mixture of carbon source in the production of gibberellic acid by Gibberella fujikuroi

Abstract

Gibberellic acid has been known since 1954 but its effect on rice still remains very important in the agricultural world. Gibberellic acid (GA₃) is the main secondary metabolite produced by the Gibberella fujikuroi fungus. This hormone is of great importance in agriculture and the brewing industry, due to its fast and strong effects at low concentrations (μg) on the processes of growth stimulation, flowering, stem elongation, and germination of seeds, among others. Plant promoters of growth production such as the gibberellins, especially the GA₃ are a priority in obtaining better harvests in the agricultural area and by extension, improving the food industry. Three routes to obtaining GA₃ have been reported: extraction from plants, chemical synthesis and microbial fermentation. The latter being the most common method used to produce GA₃. In this investigation, glucose-corn oil mixture was used as a carbon source on the basis of 40 g of carbon in a 7 L stirred tank bioreactor. A pH of 3.5, 29°C, 600 min⁻¹ agitation and 1 vvm aeration were maintained and controlled with a biocontroller connected to the bioreactor, throughout the entire culture time. The carbon source mixture affected the fermentation time as well as the production of the GAs. The production of 380 mg GA₃L⁻¹ after 288 h of fermentation was obtained when the glucose-corn oil mixture was employed contrasting the 136 mg GA₃L⁻¹ at 264 h of culture when only glucose was used.