New advances in the formulation of the biopreservative strain CPA-7 of Pseudomonas graminis

Abstract: The biopreservative strain CPA-7 of Pseudomonas graminis has shown its potential for inhibiting growth of foodborne pathogens such as Salmonella, Listeria monocytogenes and Escherichia coli O157:H7 in fresh-cut fruit. However, little success rate of biocontrol agents based products are available in the market mainly due to the maintenance of product shelf-life and efficacy. Therefore, the aim of this study was to obtain a P. graminis CPA-7-based product that maintained the viability over time. To achieve this objective, CPA-7 fresh cells grown on an optimized soy protein based medium were harvested by centrifugation, concentrated and formulated using two different techniques: a) liquid formulation (CPA-7 cells suspended in liquid solutions with different protective substances) and b) freeze-drying formulation (CPA-7 fresh cells amended with different protective substances and then freeze-dried). All CPA-7-based products were maintained under refrigeration conditions (4 °C) and the effect of protectants on cell viability and storage stability was determined. According to results obtained, liquid formulation could not be considered suitable because some shortcomings as limited shelf-life but freeze-drying has allowed to improve the formulation of CPA-7. The stable freeze-dried products obtained combined with disinfectant methods could be an additional hurdle to ensure the microbiological safety of minimally processed fruit as well as a promising tool to cover consumer demand for additive-free products.