PCR screening of an African fermented pearl-millet porridge metagenome to investigate the nutritional potential of its microbiota

Cereal-based fermented foods as a source of folate and cobalamin: The role of endogenous microbiota

Folate (vitamin B9) and cobalamin (vitamin B12) deficiencies potentially affect millions of people worldwide, leading to different pathologies. In Ethiopia, the diet is characterized by high consumption of fermented cereal-based foods such as injera, a good source of folate but not of cobalamin, which is only found in foods of animal origin that are rarely consumed. Some of the bacteria responsible for the fermentation of cereals can synthesize cobalamin, but whether or not fermented cereal food products contain cobalamin remains underexplored. The objective of this study was to assess the folate and cobalamin content of injera collected from various households in Ethiopia at different stages of production. Global (16S rRNA gene sequencing) and specific (real-time PCR quantification of bacteria known for folate or cobalamin production) bacterial composition of these samples was assessed. UPLC-PDA was used to identify the cobalamin to see whether the active or inactive form was present. Surprisingly, teff flour contained 0.8 μg/100 g of cobalamin, most probably due to microbial contamination from the environment and the harvesting process. While fermentation increased the folate and cobalamin content in some households, their levels decreased in others. Conversely, cooking consistently reduced the level of the vitamins. Fresh injera contained, on average, 21.2 μg/100 g of folate and 2.1 μg/100 g of cobalamin, which is high, but with marked variation depending on the sample. However, the form of cobalamin was a corrinoid that is biologically inactive in humans. Injera fermentation was dominated by lactic acid bacteria, with significant correlations observed between certain bacterial species and folate and cobalamin levels. For example, a high proportion of Fructilactobacillus sanfranciscensis, a known folate consumer, was negatively correlated with the folate content of injera. On the contrary, Lactobacillus coryniformis, known for its cobalamin synthesis ability was present in high proportion in the cobalamin-rich samples. These findings highlight the complex interrelationship between microorganisms and suggest the involvement of specific bacteria in the production of folate and cobalamin during injera fermentation. Controlled fermentation using vitamin-producing bacteria is thus a promising tool to promote folate and cobalamin production in fermented food.

Selection of nitrite-degrading and biogenic amine-degrading strains and its involved genes

Objectives

Accumulation of nitrite and biogenic amines (BAs) in fermented meat products is a matter of public health concern. The study aimed to screen nitrite-degrading and BA-degrading strains from sour porridges and sausages and bacon products in China.

Materials and Methods

After screening out 12 strains, the degradation of nitrite, the degradation of BAs, the activities of nitrite-reducing enzymes, and the detection of genes involved in the BAs were assessed by spectrophotometry method with hydrochloric acid naphthalene ethylenediamine, high-performance liquid chromatography, GENMED kit, and polymerase chain reaction, respectively.

Results

Pediococcus pentosaceus labelled M SZ1 2 and M GC 2, Lactobacillus plantarum labelled M SZ2 2, and Staphylococcus xylosus labelled Y CC 3 were selected. The activity of nitrite-reducing enzyme in M SZ2 2 was 2.663 units/mg. The degradation rate of total BAs of M SZ2 2 was 93.24%. The degradation rates of nitrite and BAs of M SZ1 2 were 86.49% and 37.87%, respectively. The activity of nitrite-reducing enzyme in M SZ1 2 was up to 1.962 units/mg. M GC 2 showed higher degradation rates of nitrite (89.19%) and Y CC 3 showed higher degradation rates of BAs (36.16%). The genes encoding the multicopper oxidases (suf I/D2EK17) were detected in the four strains, which also did not contain BAs (histidine decarboxylase (hdc), tyrosine decarboxylase (tdc), ornithine decarboxylase (odc), lysine decarboxylase (ldc)) formation encoding genes.

Conclusion

These four strains (M SZ1 2, M GC 2, M SZ2 2, and Y CC 3) are promising candidates to use as starter cultures for nitrite and BAs in fermented sausages.

Influence of fermentation and other processing steps on the folate content of a traditional African cereal-based fermented food

Folate deficiency can cause a number of diseases including neural tube defects and megaloblastic anemia, and still occurs in both developed and developing countries. Cereal-based food products are staple foods in many countries, and may therefore be useful sources of folate. The production of folate by microorganisms has been demonstrated in some cereal-based fermented foods, but has never been studied in a traditional African cereal based food spontaneously fermented. The microbiota of ben-saalga, a pearl-millet based fermented porridge frequently consumed in Burkina Faso, has a good genetic potential for the synthesis of folate, but the folate content of ben-saalga is rather low, suggesting that folate is lost during the different processing steps. The aim of this study was therefore to monitor changes in folate content during the different steps of preparing ben-saalga, from pearl-millet grains to porridge. Traditional processing involves seven different steps: washing, soaking, grinding, kneading, sieving, (spontaneous) fermentation, and cooking. Two type of porridge were prepared, one using a process adapted from the traditional process, the other a modified process based on fermentation by backslopping. Dry matter and total folate contents were measured at each step, and a mass balance assessment was performed to follow folate losses and gains. Folate production was observed during the soaking of pearl-millet grains (+26% to +79%), but the folate content of sieved batters (2.5 to 3.4μg/100g fresh weight) was drastically lower than that of milled soaked grains (17.3 to 19.4μg/100g FW). The final folate content of the porridges was very low (1.5 to 2.4μg/100g FW). The fermentation had no significant impact on folate content, whatever the duration and the process used. This study led to a better understanding of the impact on folate of the different processing steps involved in the preparation of ben-saalga.

Should Research on the Nutritional Potential and Health Benefits of Fermented Cereals Focus More on the General Health Status of Populations in Developing Countries?

Cereal foods fermented by lactic acid bacteria are staples in many countries around the world particularly in developing countries, but some aspects of the nutritional and health benefits of traditional fermented foods in developing countries have not been sufficiently investigated compared to fermented foods in high-income countries. Today, malnutrition worldwide is characterized by a double burden, excess leading to non-communicable diseases like obesity or diabetes alongside micronutrient deficiencies. In addition, populations in developing countries suffer from infectious and parasitic diseases that can jeopardize the health benefits provided by their traditional fermented foods. Using examples, we argue that research on traditional fermented cereals in developing countries should focus more on their effect on inflammation and oxidative stress under conditions including infectious or non-infectious gut inflammation.