Plant-based polymer as a thermoresistant carrier of phytase in Nile tilapia (Oreochromis niloticus) diets

A biodegradable soybean oil-based polymer produced following the Green Chemistry principles, was assessed as a thermoresistant vehicle of phytase aiming to improve the enzyme stability during fish diet processing. Juvenile Nile tilapia (70 +/- 4.3 g) were submitted to a digestibility assay designed in a factorial model (3 x2) to assess the polymer efficiency. The treatments comprised the combination of three phytase inclusion methods with two feed processing methods. The inclusion methods of phytase were: CPP- coating post processing, in which the enzyme was spread on top of pellets after processing, PAE- polymer associated to enzyme, which was adsorbed by the polymer and included in the ingredients mash prior feed processing and NE- no enzyme inclusion, playing a control role as phytase was not included. The feed processing methods were extrusion (120 degrees C) or pelleting (40 degrees C), exposing the polymer to different temperatures. Phytase was supplemented at 1500 units kg-1 using the CPP or PAE methods. There was a significant interaction for the apparent digestibility coefficient (ADC) values of phosphorus (P), calcium (Ca) and Ash (P < 0.05). CPP resulted in higher ADC values for P and Ca, compared to PAE and NE in extruded diets (P < 0.05). The PAE method resulted in higher ADC values of P, Ca, and Ash than NE in extruded diets (P < 0.05). In pelleted diets, PAE resulted in higher ADC values for P and Ca, and a similar ADCAsh in comparison to CPP (P < 0.05). As verified in extruded diets data, the polymer partially protected phytase from heat denaturation, resulting in higher ADC values in comparison to NE (P < 0.05). The polymer improved phytase effects in pelleted diets probably by reducing degradation in fish stomach. These results suggest that the polymer may be a potential protective carrier of phytase and other thermolabile additives in extruded and pelleted diets.

Automated summary

A biodegradable soybean oil-based polymer was evaluated as a thermoresistant vehicle for phytase in fish diet processing. The polymer showed potential in protecting the enzyme from heat denaturation and improving digestibility. It may serve as a protective carrier for phytase and other thermolabile additives in fish feed.