Biochemical characterization of phytase and xylanase produced by Aspergillus japonicus using alternative carbon sources and in vitro hydrolysis of animal feed by the enzyme cocktail

Abstract

Grains are common sources of nutrients in diets for non-ruminant animals but contain antinutritional factors that limit digestibility. A widely used solution is the addition of bioactive enzymes to diets. Filamentous fungi synthesize numerous enzymes used in the animal feed industry. This study aimed to produce and characterize phytases (PhyAj) and xylanases (XynAj) from Aspergillus japonicus and assess their potential to improve the digestibility of animal feed as compared with commercial enzymes. Enzymes were produced by solid-state cultivation using alternative carbon sources. The highest production of both enzymes was achieved in 72 h, with the wheat bran and soybean bran substrate (1:1 w/w) yielding 10.23 ± 0.63 U/g for PhyAj and 31.83 ± 2.87 U/g for XynAj. PhyAj showed optimum activity at 55 °C and pH 4.5, whereas XynAj performed best at 55 °C and pH 5.5. PhyAj increased feed degradation by 90.15 % (A4), surpassing the effects of commercial enzymes. Similarly, XynAj enhanced feed degradation by 81.64 % (A6) and diet digestibility by 88.10 % (D7), surpassing the performance of commercial enzymes. A. japonicus enzyme cocktail significantly improved nutrient release, achieving a phosphorus release of 9.44 ± 0.44 mg/g from wheat bran (A7) and a reducing sugars release of 172.40 ± 2.71 mg/g from rice grits (A1) after 24h. These findings demonstrate that A. japonicus is a promising producer of commercially relevant enzymes, holding great potential to enhance nutrient bioavailability in animal diets.