Onwuakor C.E.^1,, Ogbulie J.N.², Braide W.², Ogbulie T.E.³, Nwokafor C.V.¹, Uchendu C.E.⁴

Bacteriocins produced by various lactic acid bacteria (LAB) have found enormous use in the food industries as biopreservatives. This study evaluated the effect of varied culture conditions (temperature, pH, and NaCl concentration) on bacteriocin production by Lactococcus lactis MT186647 isolated from fermenting African oil bean seeds (Pentaclethra macrophylla Benth) using response surface methodology. A three-factor central composite design (CCD) was adopted with the interest of estimating the optimal conditions for its production using the response surface regression model, which evaluated the linear, squared, and interactive relationship between the response variables. The analysis of variance (ANOVA) using Minitab statistical software version 14.13 showed an R² = 0.869 variations in the response variable for culture conditions. It was accounted for by the predictors suggesting that the model was adequate. The optimal culture condition for bacteriocin production by L. lactis was estimated at 30.5C, pH 5.9, 1.94% NaCl concentration at Y = 12.31 mm where Y represents the response (zone of inhibition) against Staphylococcus aureus ATCC 19095 using the agar well diffusion assay method. Validation of optimal values according to the regression model, produced an inhibition zone at Y = 13.33 ± 0.29 mm. There was a 19.33% increase in bacteriocin activity compared to an OFAT optimized medium from a previous study.

Lactococcus lactis MT186647, Bacteriocin, optimization, central composite design, response surface methodology