The development of the feed industry in sustainable aquaculture activities largely relies on plant-based proteins, which are widely available and relatively inexpensive, to address the global fishmeal shortage. However, these plant-derived protein sources contain various anti-nutritional factors, such as non-starch polysaccharides, phytates, protease inhibitors, tannins, and saponins, which are less utilizable by fish, thereby limiting nutrient utilization and disrupting mineral bioavailability in aquatic species. Phytate in feed forms complexes by binding to proteins and minerals in the digestive tract of animals. These phytate-protein complexes cause problems in protein digestibility, leading to decreased digestibility, protein utilization, and growth. In addition, phytate cannot be digested by proteolytic enzymes, and the activities of enzymes such as pepsin, amylopsin, and amylase are inhibited by phytate. Feed supplementation with phytase hydrolyzes phytate, thereby releasing phosphorus from the phytate complex. As a result, phosphorus becomes freely available in the feed, playing an important role in improving the overall performance of fish and increasing the bioavailability of minerals to fish, thereby making it cost-effective and environmentally friendly. Phytase in feed promotes increased fish growth rates due to improved protein digestibility and nutrient absorption as a result of optimal function in the pyloric ceca of the intestine. The addition of phytase to feed can enhance the conversion of trypsinogen to trypsin, which breaks down proteins into amino acids, thereby increasing digestive enzyme activity and improving the digestibility of proteins and amino acids in feed that uses plant-based ingredients as protein sources.
