Bacterial community succession during traditional fermentation processes of Greenland shark (Somniosus microcephalus)

• Main Author: Snorri Páll Ólason 1997-
• Other Authors: Háskóli Íslands
• Format: Master Thesis
• Language: English
• Published: 2023
• Subjects: Líffræði; Greenland; Iceland; Somniosus microcephalus
• Online Access: http://hdl.handle.net/1946/44522

Fermented shark is a traditional delicacy from Iceland and is produced through fermentation and drying of Greenland shark. The fermentation process is a crucial step before its consumption as unprocessed shark is highly toxic. Although fermented shark has been an important source of nutrition for Icelanders for centuries, very little is known about what is behind the process of the bacterial community succession which takes place during the fermentation. For this study, experiments were conducted to evaluate if freezing/thawing of the shark would affect the bacterial community succession during the fermentation process. In addition, evaluating what effect added aeration processes would have on the succession during the fermentation period. Samples were taken throughout the process to get overall coverage of the succession by using both conventional culturing and molecular methods (16S rRNA amplicon sequencing), to quantify and identify bacteria that are responsible for the fermentation process. The conventional culturing analysis showed that the growth pattern between the same bacterial group was very similar between fresh and frozen shark cut. The 16S rRNA sequencing revealed that the fermentation process is divided into three separate phases (initial, intermediate and final phase), which are characterized by the assembly and activity of the microbial community. During the initial phase both Photobacterium and Pseudoalteromonas were dominant. The intermediate phase was characterized by the replacement of bacterial genera occupying the shark during the initial phase. During the final phase Atopostipes, Pseudomonas, Sporosarcina and Tissierella dominated the shark for the rest of the fermentation and into the drying. The freezing/thawing treatment influenced the initial bacterial community composition but as the fermentation progressed the community began to stabilize and resemble the bacterial community observed in the shark cuts of fresh fermented shark. Increased aeration did not have a significant effect on ...