Efficiency in Aflatoxin B1 Reduction in a Solid-Based Medium by Endophytes from Stipa tenacissima L. and Their In Vitro Biocontrol and Plant Growth-Promoting Properties

The goal of the present work was to investigate the interaction between endophytic bacterial isolates and Aspergillus flavus, with a specific focus on determining the occurrence of mutual antagonism upon contact. Aflatoxin B1 (AFB1) is a highly potent hepatic carcinogen produced by filamentous fungi. To decrease the amount of AFB1 in food products, nine strains of endophytic bacteria were evaluated for their efficacy in reducing AFB1 production; all of these strains were obtained from the roots of Stipa tenacissima L., an indigenous plant to the Algerian steppe. These endophytic bacterial isolates were selected as potential candidates due to their rapid growth. After a co-incubation period of 10 days in vitro, AFB1 analysis indicated that those nine isolates caused a decrease in AFB1 residual concentration by 10.04 to 98.44%, depending on the isolate. The two most efficient strains were ST01 and ST07, which showed 89.96 and 73.46% reduction of AFB1, respectively. The results of 16S rRNA gene sequencing revealed a strong genetic relationship between the two isolates and the species Acinetobacter calcoaceticus and Bacillus velezensis, respectively. These two isolates were subjected to characterization for their in vitro plant growth promotion (PGP) activity, including ACC-deaminase activity, IAA production, inorganic phosphate solubilization, and the production of siderophores and hydrogen cyanide. Based on the obtained findings, it is postulated that the aforementioned isolates hold potential as biofertilizers and biocontrol agents in combating AFB1 while posing a minimal danger to the ecological balance of microbial communities.