Optimization of Bacterial Strains and Development of Fermented Seaweed

Sammanfattning: This study aimed to understand the exploitation of bacterial strains used in various combinations to assist in the fermentation of seaweeds. The topic stems from the need to consider the valorization of seaweeds due to their abundance in natural habitats as well as their use as an innovative and sustainable food. Fermentation is a traditional method that has been utilized for food preservation. It offers beneficial properties in addition to constituting a sustainable solution. Seaweed is an aquatic flora that is divided into three categories; brown, red, and green. In this study, the brown seaweed Alaria esculenta was considered. The starter cultures contained utilizing commercially procured lactic acid bacteria in their freeze-dried forms. The main species selected for this study were Lactobacillus strains; mainly involving L. plantarum, L. casei, L. paracasei, and L. rhamnosus. Given that glucose and mannitol form some of the main saccharides readily available in brown seaweeds, they were evaluated as substrates to be utilized for the growth of the combined lactobacilli strains. Subsequently, it was seen that all the combinations of the bacterial strains were able to use mannitol and glucose as substrates, by bringing about a pH drop in an industrially relevant timeframe. Analyzing the substrate consumption, it was found that mannitol consumption was over 50% in most of the combinatorial co-cultures. Estimating the short-chain fatty acids in mannitol samples, it was observed that lactic, propionic and butyric acid were the only significant acids detected. Consequently, the bacterial combinations were applied for the fermentation of seaweeds. Upon analysis of the results, the optimal combination of bacterial strains was not identified due to equal amounts of positive results involving the samples. The seaweed fermentation experiments lasted 6 days although the pH decreased to 4.5 after 1 day. The optical density was closely correlated to the growth of the bacterial strains, which was also increased after 1 day in all of the co-cultures. As a long-term goal, the fermentation process is aimed to be designed to not only help improve the seaweed’s nutritional and storage properties but also to create a commercial product empowered with a consumer-friendly taste and smell.