Statistical Optimization for the Development of a Culture Medium Based on the Juice of Waste-Dates for Growth of Lactococcus lactis LCL Strain by Using the Plackett–Burman and Response Surface Methodology

Abstract

The processing industries of dates in Algeria, as elsewhere in other countries, generate very considerable quantities of waste. The purpose of our approach to valorize this dates-waste by using them to achieve at the formulation of a new culture medium for Lactococcus lactis, which is the most widely, used bacteria in the world for most mesophilic dairy starters. A statistical approach was used to investigate the formulation and optimization of a culture medium containing dates juice for the growth of Lactococcus lactis LCL strain. The application of Plackett–Burman screening design was enabled reveals the most significant variables for the biomass production (dates juice, buffer and yeast extract), which were retained for second optimization using a central composite design methodology, leading to determine the optimal concentrations for a maximum growth of Lactococcus lactis LCL strain. The investigated optimal concentrations for a maximum growth were 7% dates juice, 2.6 g/l yeast extract and 250 mM phosphate buffer K2HPO4/NaH2PO4. For these parameters, the maximum cell density of the Lactococcus lactis LCL strain was obtained with a coefficient of determination (R2) of 0.924 for the proposed model, thus demonstrating its robustness. The obtained culture medium in this study containing dates juice represents a favorable medium for the growth of Lactococcus lactis LCL strain improving significantly its growth approximately 30% compared with the M17 medium and that showed a cost about 5 to 6 times lower, than that which is commonly used in the world.