Biofilm Mode of Cultivation Leads to an Improvement of the Entomotoxic Patterns of Two Aspergillus Species

Abstract

Two fungi, i.e., Aspergillus flavus Link and Aspergillus oryzae (Ahlb.) E. Cohn, were cultivated according to two methodologies, namely submerged and biofilm cultures with the primary aim to use their secondary metabolites the supernatant CL50, and CL90 varied between 1.3% (v/v) to 12.7% (v/v) for incubation times from 24 to 72 h. While the A. flavus supernatant entomotoxicity was higher than this of A. oryzae, the biofilm culture application increased the efficiency of the former. Proteomic analysis of the supernatants revealed discrepancies among the two species and modes of cultivation. Furthermore, the secondary metabolite profiles of both Aspergillus cultures were verified. Aspergillic acid, beta-cyclopiazonic acid, cyclopiazonic acid, ferrineospergillin, flavacol, and spermadin A were most predominant. Generally, these secondary metabolites were present in higher concentrations in the supernatants of A. flavus and biofilm cultures. These molecular identifications correlated positively with entomotoxic activity. Noteworthy, the absence of carcinogenic aflatoxins was remarkable, and it will allow further valorization to produce A. flavus to develop potential biopesticides.

From Diverse Origins to Specific Targets: Role of Microorganisms in Indirect Pest Biological Control

“…One important challenge is the up-scaling of microbial production based on adapted technologies to improve production efficiency to be easier and less expensive. Efforts are being made to optimize microbial growth on grain residues (such as for Metarhizium, Beauveria, and Aspergillus fungi) associated to innovative biofilm techniques or in bioreactors with best adapted media and conditions (such as for Bacillus, Pseudomonas and other bacteria) [110]. New strategies for pest biocontrol may come from the microorganisms from the insects themselves (associated to endosymbionts or gut microbes).…”

Optimization of fungicidal and acaricidal metabolite production by endophytic fungus Aspergillus sp. SPH2

“…Considering that the morphology of the fungus in submerged media affects its productivity, semi-solid-state fermentation (Semi-SSF), in which the fungus grows in a biofilm, allows the production of secondary metabolites in high quantities (Barrios-González 2012 ; Francis et al 2020 ). This method involves the use of techniques that impede the formation of fungal agglomerates, resulting in smaller, less dense pellets or even dispersion of the mycelium throughout the growth medium (Kowalska et al 2018 ), leading to more efficient substrate consumption, much greater oxygen transfer, and increased productivity of the fungus.…”

Optimization of Fungicidal and Acaricidal Metabolite Production by Aspergillus sp. SPH2

“…Considering that the morphology of the fungus in submerged media affects its productivity, semi-solid-state fermentation, in which the fungus grows in a biofilm, allows the production of secondary metabolites in high quantities [13,14]. One optimization approach includes techniques that interfere with the formation of fungal conglomerates, causing the pellets to be smaller, less dense, or even the mycelium to be dispersed in the culture medium [15], leading to more efficient substrate consumption, much greater oxygen transfer, and increased productivity of the fungus.…”