Current knowledge on the dual species interaction and biofilm between Aspergillus and Bacillus : exploiting molecular understanding toward applications

The complex interaction between Aspergillus and Bacillus has been gaining attention with the evolution of their co-culture applications. Information reported on this interaction from different points of view including both synergistic and antagonistic mechanisms necessitates a review for better understanding. This review focuses on the interaction, biofilm formation, and the diverse biotechnological applications of Aspergillus and Bacillus, giving special attention to Aspergillus niger and Bacillus subtilis. The review demonstrates that co-cultivation of Aspergillus and Bacillus exhibits significant transcriptional changes, impacting metabolism and secondary metabolite production in both organisms. Signaling from living fungal hyphae, EPS production, TasA fibrils, and regulators like Spo0A are essential in forming biofilm communities. Nutrient availability and pH levels, species type, and mutations in EPS-producing genes may also influence whether Bacillus will act antagonistically or synergistically with Aspergillus. This dual-nature complex interaction activates silent genes synthesizing novel compounds mainly with antifungal and medicinal properties, showcasing its potential for diverse applications in various fields such as agriculture and crop protection, bioremediation, environmental biotechnology, food science and fermentation, industrial biotechnology, and medical biotechnology and health. The use of Aspergillus and Bacillus species has evolved from simple monoculture applications to more sophisticated co-cultures and has been trending toward their synergy and metabolic optimization.