Bioaccumulation of Heavy Metals and Optimization of Lipase Production by Lysinibacillus sphaericus Strain ODE16_EKITI Isolated from Domestic Oil-Rich Wastewater

In a bid to remediate the menace caused by the presence of lipids in many biological wastewater treatment systems, various researchers have focused on a way to explore lipase production by different microorganisms for this purpose. Some cultural parameters were hence optimized while their influences on the production of lipase by Lysinibacillus sphaericus strain ODE16_EKITI in an oil-rich wastewater were enumerated using standard laboratory techniques. Inorganic content of the sample and lipase production were estimated using atomic absorption spectrophotometry and lipase colorimetry respectively. Magnesium (Mg) constituted the highest metal concentration of 54.5mg/L while least concentration of calcium (Ca) (13.4mg/L) in the wastewater sample and iron (Fe) as the only heavy metal detected in high concentration (31.6mg/mL). No significant difference in the accumulation potential of the consortium that took up 77.85% of phosphate and that of the organism, which accumulated 77.38% of phosphates in the sample. The maximum lipase activity (5.111mMol) was recorded after 5 days’ incubation, with the production rate of 0.78mM/min daily and the microbial growth rate of 0.292 mg/day. The organism had the highest growth (OD 0.298) and lipase production (6.667mMol) with oil concentration of 2.5ml/L at optimum temperature of 30oC. L. sphaericus also showed the highest growth (with OD 0.301) and lipase production of 6.67mMol in the presence of magnesium ion (Mg2+). The present work has offered us the chance to explore a lipolytic bacterium, Lysinibacillus sphaericus strain ODE16_EKITI that can produce lipase ranging between 5.1mMol to 6mMol at 30oC and 2.5% palm oil concentration after 5 days. This organism also showed potentials for bioaccumulation of some heavy metals. L. sphaericus strain ODE16_EKITI is thereby presented as a promising tool for biotechnological exploitation in remediation of domestic oil-rich wastewater.