Abstract
The production of a predictive mathematical model for Lactobacillus plantarum batch culture was achieved through the development of a synthetic medium. Analysis of the medium during a liquid culture enabled the identification of components essential for growth. These were then introduced to the mathematical model and their effect on the viability and biomass concentration of L plantarum ascertained. Viability is the important factor, as it determines the amount of product produced from each culture and the monetary value of each culture. This had not been previously incorporated into a mathematical model so a novel approach was required. Once this was achieved, the effect of amino acids on viability was simulated. Promising amino acids were then used in a culture. The results were in agreement with the model's predictions. A working predictive model had therefore been produced. The study of the culture through the simulation produced a protocol designed to prevent the decrease in viable count observed at the end of the culture. This is currently being evaluated by Interprise Ltd. Interprise Ltd produce freeze-dried Lactobacillus plantarum for use as a silage starter culture. They experienced a decrease in culture viable count of 75% (8.00x109 CFU/ml. to 2.00x109 CFU/ml.) with no change in the process conditions. Operating the process at 30°C with filter sterilised medium improved the process. The final viable count attained 1.50x1010 CFU/ml, an 1000% increase on the current process production viable counts by Interprise Ltd. A further improvement was achieved by increasing the yeast extract concentration by 10%. The increased medium cost (7%) was offset by a 15% increase in culture yield. The reduced operating temperature also reduced running costs. Interprise Ltd have implemented these findings into their production process.