Modeling conditions for producing bacteriocin using supplemented whey permeate.

Various types of growth conditions have been associated with the production of bacteriocins. The commercial application of bacteriocins depends on optimizing their production, either by modifying genetic determinants or environmental growth parameters.

You can reduce the cost of bacteriocin production by determining the optimum production parameters and using alternative growth media. This can be achieved by establishing the significance of factorial interactions between variables. The objective is to reach the optimal conditions by incorporating factorial designs and response surface methodology.

The objective of scientists in Mexico was to model conditions that lead to high bacteriocin activity by L. lactis using supplemented whey permeate as an alternative medium. The researchers also wanted to study the antagonistic activity of bacteriocins against L. monocytogenes. A 26-2 fractional factorial design was used to screen for factors that affect bacteriocin production in a shake culture. Significant factors were used for further optimization in a central composite design. The investigators tested the most suitable growth conditions to maximize bacteriocin production using a 3-L bioreactor.

A second order model yielded good agreement with experimental data. The conditions leading to maximum activity in a shake culture included: whey permeate at 71 g per L; yeast extract at 30 g per L; MgSO4 at 0.35 g per L; and MnSO4 at 0.07 g per L.

Under these conditions, bacteriocin activity increased by four times the initial value--1,600 AU per mL. After scaling up, the activity increased by 16 times to 25,600 AU per mL. The minimum inhibitory concentrations for L. monocytogenes were 6,400 AU per mL and 15,000 AU per mL in culture medium and in skimmed milk, respectively. A mixed culture of this pathogen with L. lactis UQ2 gave a 10-log population reduction, and an 8-log decrease using the cell free extract (6,400 AU per mL).

Bacteriocin activity greatly increased using this low-cost alternative medium and scaleable production method. L. monocytogenes was significantly inhibited by the bacteriocin and the producing strain.

Further information. B. E. Garcia-Almendarez, Investigacion y Posgrado en Alimentos, Biotechnology Group, Propac, Facultad de Quimica, Universidad Autonoma de Queretaro, C.U., Cerro de las Campanas S/N, Queretaro, Qro., 76010, Mexico; phone: [phone]; fax: [phone]; URL: www.uaq.mx.