Alternative methods for gibberellic acid production, recovery and formulation: A case study for product cost reduction.

The aim of this work was to develop a new production, recovery and formulation process of gibberellic acid (GA3). Low-cost byproducts - citrus pulp (CP) and soybean hulls (SH) - were employed as substrate for GA3 production by Gibberella fujikuroi in semisolid fermentation. A CP/SH mixture (70%/30%) promoted high productivities both in bubble column reactor (1.66 mg L/h), and in stirred tank reactor (2.13 mg L/h). GA3 production medium cost (US$ 6.70/m3) was reduced by 85% when compared to previously reported synthetic media (US$ 44.96/m3). It was described that GA3 fermented extract has low stability, and that liquid and powder formulation of the fermented extract maintained the biomolecule activity over 6 months. Alginate and alginate/kefiran beads containing GA3 showed encapsulation efficiency of 70% and 60%, respectively. This work supports good perspectives for GA3 production using cheap substrates and simple formulation of clarified extract to favour its use in agricultural countries.

Current advances in gibberellic acid (GA3) production, patented technologies and potential applications.

MAIN CONCLUSION: Gibberellic acid is a plant growth hormone that promotes cell expansion and division. Studies have aimed at optimizing and reducing production costs, which could make its application economically viable for different cultivars. Gibberellins consist of a large family of plant growth hormones discovered in the 1930s, which are synthesized via the terpenes route from the geranylgeranyl diphosphate and feature a basic structure formed by an ent-gibberellane tetracyclic skeleton. Among them, only four have biological activity, including gibberellic acid (GA3), which acts as a natural plant growth regulator, especially for stem elongation, seed germination, and increased fruit size. It can be obtained from plants, fungi, and bacteria. There are also some reports about microalgae GA3 producers. Fungi, especially Gibberella fujikuroi, are preferred for GA3 production via submerged fermentation or solid-state fermentation. Many factors may affect its production, some of which are related to the control and scale-up of fermentation parameters. Different GA3 products are available on the market. They can be found in liquid or solid formulations containing only GA3 or a mixture of other biological active gibberellins, which can be applied on a wide variety of cultivars, including crops and fruits. However, the product's cost still limits its large and continuous application. New low-cost and efficient GA3 production alternatives are surely welcome. This review deals with the latest scientific and technological advances on production, recovery, formulation, and applications of this important plant growth hormone.

Gibberellic Acid Production by Different Fermentation Systems Using Citric Pulp as Substrate/Support.

Gibberellic acid (GA3) is an important phytohormone, a member of gibberellins family, which acts as a promoter and regulator of plant growth. This study aimed to evaluate GA3 production by Fusarium moniliforme LPB03 and Gibberella fujikuroi LPB06 using different techniques of fermentation, solid state fermentation (SSF), submerged fermentation (SmF), and semisolid state fermentation (SSSF), and different types of bioreactors. In all techniques, citric pulp (CP), a subproduct obtained from the extraction of orange juice, was employed as the substrate/support. GA3 production by SSF reached 7.60 g kg-1 and 7.34 g kg-1 in Erlenmeyer flasks and column bioreactors, respectively. For SmF, the highest concentration of GA3 obtained was 236.00 mg L-1 in Erlenmeyer flasks, 273.00 mg L-1 in a 10 L stirred tank reactor (STR), and 203.00 mg L-1 in a 1.5 L bubble column reactor (BCR). SSSF was conducted with a CP suspension. In this case, GA3 concentration reached 331.00 mg L-1 in Erlenmeyer flasks and 208 mg L-1 in a BCR. The choice of the fermentation technique is undoubtedly linked to the characteristics and productivity of each process. The methods studied are inexpensive and were found to produce good proportions of GA3, making them suitable for several applications.