Biocontrol efficacy of atoxigenic Aspergillus flavus strains against aflatoxin contamination in peanut field in Guangdong province, South China

Response of broilers to dietary inclusion of atoxigenic Aspergillus flavus strain as a biocontrol strategy of aflatoxin

The objective of this trial was to evaluate how broilers responded to Aspergillus flavus strains that are toxigenic and atoxigenic. The study included four treatments in a 2 × 2 factorial design, with six replicates of 10 birds each. As a result of this study measuring feed intake (FI), weight gain (WG), feed conversion ratio (FCR), crude protein, ether extract, and crude fibre, the interaction was insignificant between the toxigenic and atoxigenic diets (P > 0.05). Consumption of toxigenic aflatoxin B1-500 ppb diet decreased FI and WG but increased FCR, and cost to produce live broiler weight (P < 0.05) compared to the control diets. The addition of atoxigenic strains to contaminated diets significantly offset (P < 0.05) the effects. Diets with or without 500 ppb toxigenic and atoxigenic A. flavus did not affect the relative weight g/100gBW of pancreas, gizzard and bursa of Fabricius. Dietary inclusion of 500 ppb toxigenic Aspergillus spp. increased the relative weight (P < 0.05) of the kidney, liver, spleen and thymus while atoxigenic dietary addition reduced the relative weight of the same organs (P < 0.05). Dietary inclusion of toxigenic and atoxigenic Aspergillus spp. did not significantly affect the haematological parameters measured (P < 0.05). Dietary inclusion of 500 ppb toxigenic Aspergillus elevated the urea, creatine, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) in the serum of the broilers (P < 0.05). A decrease was observed when atox igenic A. flavus was used in the intervention for urea, creatinine and AST (P < 0.05), whereas an insignificant reduction was observed for ALT and ALP (P ≤ 0.05). This study concluded that dietary atoxigenic strain improved broiler performance, digestibility, and blood parameters.

Creating large chromosomal segment deletions in Aspergillus flavus by a dual CRISPR/Cas9 system: Deletion of gene clusters for production of aflatoxin, cyclopiazonic acid, and ustiloxin B

Aspergillus flavus produces hepatocarcinogenic aflatoxin that adversely impacts human and animal health and international trade. A promising means to manage preharvest aflatoxin contamination of crops is biological control, which employs non-aflatoxigenic A. flavus isolates possessing defective aflatoxin gene clusters to outcompete field toxigenic populations. However, these isolates often produce other toxic metabolites. The CRISPR/Cas9 technology has greatly advanced genome editing and gene functional studies. Its use in deleting large chromosomal segments of filamentous fungi is rarely reported. A system of dual CRISPR/Cas9 combined with a 60-nucleotide donor DNA that allowed removal of A. flavus gene clusters involved in production of harmful specialized metabolites was established. It efficiently deleted a 102-kb segment containing both aflatoxin and cyclopiazonic acid gene clusters from toxigenic A. flavus morphotypes, L-type and S-type. It further deleted the 27-kb ustiloxin B gene cluster of a resulting L-type mutant. Overall efficiencies of deletion ranged from 66.6 % to 85.6 % and efficiencies of deletions repaired by a single copy of donor DNA ranged from 50.5 % to 72.7 %. To determine the capacity of this technique, a pigment-screening setup based on absence of aspergillic acid gene cluster was devised. Chromosomal segments of 201 kb and 301 kb were deleted with efficiencies of 57.7 % to 69.2 %, respectively. This system used natural A. flavus isolates as recipients, eliminated a forced-recycling step to produce recipients for next round deletion, and generated maker-free deletants with sequences predefined by donor DNA. The research provides a method for creating genuine atoxigenic biocontrol strains friendly for field trial release.

Aflatoxins Contamination in Feed Commodities: From Occurrence and Toxicity to Recent Advances in Analytical Methods and Detoxification

Synthesized by the secondary metabolic pathway in Aspergilli, aflatoxins (AFs) cause economic and health issues and are culpable for serious harmful health and economic matters affecting consumers and global farmers. Consequently, the detection and quantification of AFs in foods/feeds are paramount from food safety and security angles. Nowadays, incessant attempts to develop sensitive and rapid approaches for AFs identification and quantification have been investigated, worldwide regulations have been established, and the safety of degrading enzymes and reaction products formed in the AF degradation process has been explored. Here, occurrences in feed commodities, innovative methods advanced for AFs detection, regulations, preventive strategies, biological detoxification, removal, and degradation methods were deeply reviewed and presented. This paper showed a state-of-the-art and comprehensive review of the recent progress on AF contamination in feed matrices with the intention of inspiring interests in both academia and industry.