Role of Microbial Phytases in Improving Fish Health

Fishmeal is the most preferred protein source in aquafeed industry due to its balanced amino acid and fatty acid profile, but its limited global supply and high price value, necessitates researchers to focus on sustainable alternative sources of protein and plant-based feed, to meet the growing demand of fish feed. Phytate is a reservoir of phosphorus present in the plants; however, its chelating ability makes it anti-nutritional. Phytate forms complexes with minerals, proteins, lipids and carbohydrates, confining their accessibility in fish feeds, hence, additional dietary nutrients are required in the fish feed to overcome nutritional deficiencies. The elimination of phytate-phosphorus through animal faeces and its pass on to aquatic bodies leads to enrichment of nutrients, eutrophication and algal blooms. Microbial phytase segregates phosphorus, minerals, proteins and lower inositol phosphates from phytate. The supplementation of fish feed with microbial phytase enhances the digestibility of minerals, due to which less nutrients are excreted in the faeces; therefore, minimizing pollution in water bodies. Monogastric and agastric animals inherently exhibit the deficiency of phytase; hence, supplementation of dietary material with phytase has been an emerging choice to make dietary nutrients available for fish. Moreover, microbial phytases have a broad pH range and are thermostable, which makes them an excellent choice for commercial fish feed production. Additionally, microbial phytase improves fish growth as these enzymes enhance nutrients bioavailability and their digestion. This review article presents the application of microbial phytases as a feed additive, and their role in enhancing fish growth.