Isolation, characterisation and efficacy of the bacterial strain Lysinibacillus sphaericus YMM in biodegradation of malathion insecticide in liquid media

ABSTRACT

A new isolate of bacterium Lysinibacillus sphaericus YMM capable of degrading malathion insecticide in liquid media was isolated and characterised. Biodegradation factors were investigated using Plackett–Burman factorial design, and the rest of the insecticide was monitored by high-performance liquid chromatography analysis. The near optimum conditions for degradation of 200 mg malathion/L were 30 mL medium, 2% of L. sphaericus suspension (0.70 OD_600nm), pH 5,10 g/L glucose, 1.0 g/L NaCl, 0.3 g/L MgSO₄, 1.0 g/L NH₄Cl and incubation for 24 h without yeast extract and peptone or beef extract. In addition, the significant variables including the medium volume, inoculum and incubation time were further optimised using Box–Behnken response surface design. These conditions were found to be 30.10% medium and inoculum of 0.706 (OD_600nm) for 23.636 h of incubation to achieve 98.974% degradation. Therefore, L. sphaericus YMM showed a potential degradation of malathion. Further studies should be conducted to understand the mechanism of biodegradation in liquid media.

KEYWORDS:

• Malathion
• biodegradation
• Plackett–Burman
• Box–Behnken
• HPLC
• Lysinibacillus sphaericus

Disclosure statement

No potential conflict of interest was reported by the authors.