Authors: Adarsh Kumar Puri, Johnson Zininga, Kugenthiren Permaul, Suren Singh
Abstract: The phosphorous present in phytic acid (inositol hexakisphosphate) cannot be digested by monogastric animals and it poses major environmental problems such as water pollution and algal blooms, which in turn has adverse effects on the diversity of fauna and flora. Phytase (myo-inositol-hexakisphosphate phosphohydrolase) is routinely used as food and feed additive that hydrolyses inositol hexakisphosphate into inositol and orthophosphates, and therefore minimizes the environmental phosphate load. The present study focuses on statistical optimization of culture variables affecting production of a robust phytase from a thermotolerant compost isolate in submerged fermentation. The isolate was identified as Bacillus ginsengihumi based on its microscopic and molecular characteristics. Plackett-Burmann (PB) methodology was employed to identify incubation time, pH, temperature and the concentration of vitamin cocktail as significant factors. Further optimisation by Response Surface Methodology (RSM) resulted in an overall 4.2-fold increase in phytase production, which was validated in shake flask and in a 5 l laboratory bioreactor. The enzyme is catalytically active over an expanded temperature (50 to 90°C) and pH (2.0 to 10.0) range, showing optimal activity at 70°C and pH 4.0. Additionally, the enzyme was fairly stable with pepsin under physiological conditions. Overall, this study shows that a new compost isolate Bacillus ginsengihumi has the potential to produce significant titres of a thermo- and pH-stable phytase, which could find applications in the animal feed industries.
Keywords: Thermo-acid-stable; Protease-resistant; Phytase; Bacillus ginsengihumi; Sugarcane bagasse