Assembly of a synthetic microbial community to ferment rice (Oryza sativa) bran for aquaculture feedstuff

Raw materials of plant origin, such as rice bran (Oryza sativa; RB), are promising alternatives to fishmeal in aquaculture feeds, offering a low-cost solution. However, due to antinutritional factors and reduced digestibility, direct use of RB is limited. Fermentation is an effective, cost-effective, and environmentally friendly technique that improves the nutritional quality of RB, enhancing nutrient availability and digestibility and reducing harmful compounds. Fermented RB improved growth, feed utilization, immune competence, and gut health, contributing to more sustainable aquaculture practices. The study aimed to evaluate the solid-state fermentation influence of a synthetic microbial community (SynCom) on RB (RBMC). The fermentation by the microbial consortium showed significant changes in RB physical-chemical composition and crude fiber and protein. Significant reductions were observed for ether extract, mineral matter, phosphate, phosphorus, and potassium compared with the naturally fermented RB (RBNF). Sodium, calcium, and iron contents increased by 43.03, 60.77, and 74.58%, respectively, compared to RBNF. A significant increase was observed in the fermented RBMC for essential and non-essential amino acids. Scanning electron microscopy revealed changes in the microstructure of the RB, in addition to the presence of microbial aggregates morphologically similar to the individuals used as inoculum. The RB fermentation using SynCom significantly improved the quality of the RB by-product feedstuff. The use of fermented RB in diet formulations for aquatic organisms is desirable because it enables the reuse of this industrial co-product, which is rich in nutrients and biological value.