Nutrient stress as a means to enhance the storage stability of spray dried microencapsulated Lactobacillus plantarum B21

Lactobacillus plantarum B21 is a bacteriocin producing strain of lactic acid bacteria. Bacteriocin is a natural antibiotic that has high potential as a biopreservative. The incorporation of L. plantarium B21 into food products has potential for extending the shelf-life of food. Producing stable cultures of this microbe that can survive industrial processing is therefore of great interest. In this study the effect of nutrient stress, in particular the omission of a major carbohydrate source from the growth medium, was investigated as a method to increase L. plantarum B21 stability over 8 weeks. This treatment was found to produce cells with significantly improved storage stability and survivability compared to unstressed cells. Critically, these cells also retained the capacity to produce functional bacteriocin, as assessed by the well diffusion assay and electron microscopy measurements. Stress induced via the omission of Tween 80 in the growth medium did not enhance cell survival during spray drying and during storage and led to a loss of functional bacteriocin production when the bacteria were stored at 22 °C and 30 °C respectively. The results from this study provide insights into the optimal growth conditions needed to produce robust and stable B21 microculture for food preservation purposes.