Phytase is an enzyme of great importance because it is added as a biofertilizer to soil and added in animal feed to increase the uptake of inorganic phosphorous. Phytase production is the property of plant growth promoting rhizobacteria (PGPR) that harbor in rhizosphere part of the soil. These phytase producing bacteria can be utilized as biofertilizers as and can increase the soil fertility and crop production.
Soil samples were collected and screened for the production of phytase (an extracellular) enzyme on phytase screening media (PSM). Six bacterial isolates (PHY02, PHY03, PHY06, PHY07, PHY12, and PHY30) showed distinguished clear zones (> 6mm) on PSM. Isolates were identified as Lactobacillus casei PHY02, Enterobactor intermedius PHY03, Bacillus badius PHY06, Escherichia coli PHY07, Shigella sonnei PHY12, and Klebsiella pneumonia PHY30.
Effect of physical parameters (temperatures, pH and osmotic pressure) on growth and enzyme production by selected isolates was determined. Optimum growth and production of phytae by PHY02, PHY03, PHY06, PHY07, PHY12, and PHY30 (27, 9, 19, 40, 32, and 19 IU, respectively) was at 37°C. PHY07 showed highest enzyme production, followed by PHY30 and PHY02. Isolate PHY06 showed similar growth and enzyme activity at 37°C and 42°C but it was significantly reduced at low temperature. Effect of pH on phytase production on selected isolates indicates that all isolates produces maximum amount of phytase at pH 6.5. At pH 6.5 enzyme units released by PHY02, PHY03, PHY06, PHY07,
PHY12, and PHY30, were 26, 15, 19, 41, 19, and 32 IU, respectively. Production of enzyme decreased with the increase in osmotic pressure. PHY02, PHY03, PHY06, PHY07, PHY12, and PHY30 showed optimum enzyme production (27, 15, 17, 41, 18, and 32 IU, respectively) at 1 % NaCl in PSM (Figure 1C).
Effects of carbon source on both growth and phytase production of isolates showed that PHY03, PHY06, PHY07, PHY12 had significantly higher (P<0.05) cell densities and enzyme production in glucose, while PHY02 and PHY30 had higher enzyme activity at 0.3% lactose.
Nitrogen source in growing media also effects the growth and production of enzyme. PHY02 and PHY12 had better growth and production at 0.1% peptone, while PHY07 and PHY30 had significantly higher phytase level in media modified with peptone but at higher concentration (0.3%). Addition of tryptone in growth medium significantly enhanced the growth and enzyme production by PHY03, and PHY06.