Ultrasound pretreated rice bran for Rhizopus sp. phytase production as a feed

Abstract

Phytasae enzymes have a major role in animal feed applications as they help in the bioavailability of phosphorus present in phytic acid, an anti-nutritional compound associated with higher plant proteins. However, achieving higher levels of phytase production and phytic acid degradation is still difficult in solid state fermentation (SSF). This study involved a comparison of ultrasonication treated and untreated rice bran (RB) to improve the phytase production using Rhizopus sp. Ultrasound treatment of rice bran has been optimized with different parameters such as ultrasound time, ultrasound cycle (UC), ultrasound amplitude and liquid to solid ratio (LSR). With optimal conditions of treated RB (40 min ultrasound time, 100% ultrasound cycle (no intervals during ultrasound), 40:10 (mL/g) LSR and 80% ultrasound amplitude), a 9.3-fold increase in phytase production was observed. Different analytical methods were used to study the characteristics of treated and untreated RB such as scanning electron microscope (SEM) for morphological changes, functional group modifications using Fourier transform infrared spectroscopy (FTIR), elemental composition using energy dispersive analysis of X-rays and the crystalline nature using X-ray diffraction (XRD). With optimized conditions, phytase production was carried out and its potential activity with simulated gastric fluids were studied at pH 2.0–5.0. The thermostability of the phytase enzyme was further improved by the addition of polyvinylpyrrolidone (PVP). Thus, the ultrasound treated RB can be a potential substrate for the efficient production of phytase and as a source for a nutritive supplement that might be used in the food and feed industries.