Bioformulate to reduce the accumulation of aflatoxins in maize based on a biopolymer as a carrier and support for growth of the biocontrol agent

Abstract

Maize (Zea mays L.) is the cereal with the highest volume of production worldwide, and the second most important in Argentina. The presence of aflatoxins in the different stages of the maize agri-food chain is a current problem in food safety and it is caused by the contamination with species of Aspergillus section Flavi, mainly A. flavus. During many years the research group has focused on the development of a biological control strategy based on the competitive exclusion mechanism. Several studies have demonstrated the effectiveness of the non-toxicogenic A. flavus AFCHG2 strain developed by solid state fermentation on long grain rice. However, considering the United Nations sustainable development goal of zero hunger, it was proposed to replace this substrate and to develop a biopolymer that allows the growth and transport of the biological control agent to be applied to crops such as maize and peanuts. In this sense, different natural, economic and starch-rich substrates were analysed: cassava starch (10 and 15%), rice flour (10 and 15%) and maize starch (5, 10 and 15%). In addition, urea was added as a nitrogen source, and citric acid as promoter of greater crosslinking of starch chains. Also, the development of the biocontrol strain in polymers with the addition of glucose or sucrose was evaluated. The diameter of the pores of each polymer was determined and those with a pore diameter of 93-97 µm were selected assuming they allow a better use of the entire substrate by the biological control agent. In addition, the growth of the biological control strain in the different preparations was analysed. The synthesis of this biopolymer included stages of gelation, cooling, freezing, thawing, drying, sterilization and curing, hydration, pH regulation, inoculation, incubation and final drying. The effectiveness of the bioformulate evaluated under field showed a reduction of 81% in aflatoxin accumulation in maize kernels in comparison with the non-inoculated controls. The development of this biotechnological tool allowed us to present a process and product patent that is currently pending. In addition, it offers to producers an eco-friendly, economical and safe alternative that contributes to food quality and safety.