Spray drying of starter cultures: Diverse solutions within Lactococcus lactis to improve robustness

This thesis describes the assessment and the possible exploitation of the natural diversity within Lactococcus lactis strains with respect to robustness. Special focus was on survival during heat and oxidative stress, which are both important parameters for optimal performance and survival during spray drying of commercial dairy starter cultures. Moreover, the dynamic range that can be achieved for this industrially relevant phenotype within one strain by either varying fermentation parameters or employment of adaptive selection techniques was determined. Subsequently, various "omics"- approaches were performed, aiming to increase the understanding of the molecular mechanisms involved in spray drying robustness and to develop strategies to increase robustness of L. lactis starter cultures.