Reference Number: 174
Insect frass samples were collected from Drosophila melanogaster, Plodia interpunctella,Rhyzopertha dominica, Sitophilus granarius, Sitophilus oryzae, Sitophilus zeamais, Tribolium confusum and Tribolium castaneum to elucidate if they can be the origin of Type I sourdough micro?organisms (Lactobacillus sanfranciscensis and Candida milleri).
Methods and Results
Selective enrichments were carried out to isolate lactic acid bacteria (LBA) and yeast. A metagenetic analysis, targeted on bacterial 16S rRNA gene and fungal ITS region, was performed by using Illumina MiSeq protocol. In cultivation conditions, Lactococcus garvieae and Rhodotorula mucilaginosa were the most frequently species among LAB and yeasts respectively. The Next Generation Sequencing approach revealed that Enterobacteriaceae, Pseudomonadacae and Bacillaceae were the dominating taxa, accounting for 61% of the bacterial community. Lactobacillus genus showed a relative abundance of only 0·36%, but L. sanfranciscensis proved to be the species most frequent between lactobacilli and predominant in faecal samples of T. castaneum and T. confusumlarvae. The core fungal microbiota was constituted by Saccharomycetales, Pleosporaceae and Nectriaceae that attained the 51% of recognized OTUs. While the most abundant yeast genus was Candida (17·1%), sequences belonging to C. milleri were not found.
Frass released by the insects of stored cereal products can be the natural reservoir of L. sanfranciscensis.
SIGNIFICANCE OF THIS STUDY
There have been a number of sources suggested for the yeasts and bacteria found in a sourdough starter, including the flour, air, and the baker’s hands. This study shows that insects associated with cereal grains may potentially be a source of some sourdough microbes.
HOW DO WE INTERPRET AND USE THIS INFORMATION?
This places even more importance on using organic flour. Spraying the grain with pesticides is working against the microbes that we are trying to encourage. If you want to start or are maintaining a sourdough starter, it is important to use organic flour.