Estudo Bioquímico das Fitases e Xilanases produzidas por Aspergillus sp e Thermoascus sp usando fonte de carbono alternativas: aplicação das enzimas na ração animal

Abstract

Compounds of plant origin used in animal feed have anti-nutritional factors such as non-starch polysaccharides, oligosaccharides and phytates, which are present in the cell wall of cells of plant origin. These elements modify digestibility, residence time and viscosity in the digestive tract. Exogenous enzymes such as xylanases and phytases, produced by microorganisms, are used to promote the degradation of PNA and phytate. Thus, exogenous enzymes when added to the feed contribute to better digestibility, promoting growth and improving the productive performance of animals. Therefore, the objective of this study was to select and characterize the fungi with the best production of phytase and xylanase, from an alternative carbon source in solid medium (FMS), to later apply these enzymes in vitro in rations and perform the comparison with the enzymes commercials. Seven filamentous fungi of the genera Aspergillus sp. and Thermoascus sp. in solid fermentation and tested on different carbon sources. The best carbon source for phytase production was rice straw by Aspergillus sp. (M2) (2.73 ± 0.007 U/mg). For xylanase, it was rice straw by A. flavus (41.45 ± 13.07 U/mg). The best growth time for phytase production by A. niger was 96 hours (1.48 ± 0.07 U/mg). In the production of xylanase, the peak was observed with Aspergillus sp. (M2) in 48 hours (31.06 ± 1.50 U/mg). The optimal temperature of phytase with Aspergillus sp. (M2) and A. niger was 50 and 45 °C, respectively. The optimal temperature for Aspergillus sp. (M2) was 55°C. Whereas Aspergillus sp. (M2) was the best producer of the enzymes of interest, this fungus was defined for application in animal feed. For the in vitro enzymatic activity test, 0.05 U of crude enzymatic extract and commercial enzyme were used. Phytase from Aspergillus sp. (M2) had hydrolysis capacity in MI diet (3.38 ± 0.85 µmol/mL), while commercial phytase had greater hydrolysis capacity in MIFS (1.78 ± 0.11 µmol/mL). The xylanase enzymatic assays were performed at 4, 8 and 24 hours of incubation, using 100 µL of the enzymatic extract and the commercial enzyme. The xylanase from Aspergillus sp. (M2) obtained greater hydrolysis in the MIFS diet at 4 hours (12.67 ± 0.51 µmol/mL), 8 hours (34.36 ± 0.66 µmol/mL) and at 24 hours (38.12 ± 2, 27 µmol/ml). Commercial xylanase 2 had greater hydrolysis in the MI diet at 4 hours of incubation (8.06 ± 0.13 µmol/mL), and at 8 hours of incubation it had greater hydrolysis capacity in the MIFS diet (19.18 ± 2 .37 µmol/mL) and MI at 24 hours (26.32 ± 0.67 µmol/mL). Thus, the addition of phytase and xylanase from Aspergillus sp. (M2) in vitro diets showed an increase in sugars and inorganic phosphate released, being able to improve the absorption of nutrients, contributing to reducing production costs