The use of starter lactic acid bacteria in fermented foods, such as dairy products, affects the safety and quality of the final product. The acidification of milk by the starter cultures not only promotes the safety of the product, but also the coagulation of proteins and the formation of the gel matrix. Published research has shown that pre-treatment of mixed starter cultures of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus with mild pulsed electric fields has an effect on the rate of fermentation, the degree of proteolysis, and the firmness of the yogurt. The mechanism behind these phenotypic changes in product characteristics is thought to be due to a transient response of the starter culture to oxidative stress. In this work, the underlying mechanism will be determined by transcriptome analyses.

The production of high-quality edible vegetable oils and fats is currently based on the collection of oleaginous fruits and extraction by mechanical pressing. However, the production of oils and fats from plants requires intensive use of resources such as arable land, water and fertilizers. To meet global demand, vast areas of rainforest are cleared and converted to agricultural land, destroying ecosystems. Biotechnological production of oils and fats by oleaginous microorganisms has gained focus in the last decade and is emerging as a cost-effective alternative for environmentally friendly and socially fair production of oils and fats for human consumption. In this thesis, microorganisms with the potential to produce oils and fats are going to be isolated from agro-industrial waste in Lower Saxony, identified and characterized with respect to their yield.