In situ fortification of vitamin B12 in grain materials by fermentation with Propionibacterium freudenreichii
Year: 2020
Type: dissertation
Abstract: Vitamin B12 is a micronutrient that is predominantly present in food of animal origin. Therefore, developing plant-origin food with a nutritionally relevant content of vitamin B12 can increase the dietary intake of this vitamin among people with limited consumption of animal products. Since its chemical synthesis is overly complicated and expensive, the commercial vitamin B12 used for food fortification is exclusively produced via a biotechnological process. As compared to fortification with this commercial form of vitamin B12, in situ fortification via fermentation can be a more cost-effective alternative. As a commonly consumed staple food, grains are excellent vehicles for enrichment with micronutrients. Propionibacterium freudenreichii is the only food-grade microorganism with the ability to produce vitamin B12. Because P. freudenreichii has a low growth rate and is sensitive to acidic conditions, sterilized grain materials have mostly been used so far to produce a high vitamin B12 content. The sterilization process, however, alters the technological properties of grain-based raw materials and decreases the feasibility of the process. The present thesis focuses on in situ fortification of vitamin B12 in native grain materials by fermentation with P. freudenreichii. This study has demonstrated that fermentation of wheat flour, whole-wheat flour and wheat bran with P. freudenreichii resulted in a physiologically significant level of vitamin B12 (up to 155 ng/g dw) after 7 days. Whole-grain wheat flour and wheat bran had a higher content of vitamin B12 than refined wheat flour. However, the propagation of Enterobacteriaceae indicated that monoculture fermentation with P. freudenreichii cannot dominate the microflora, to guarantee microbial safety and control endogenous microbiota present in grain materials. Thus, an effective co-culture of Lactobacillus brevis ATCC 14869 and P. freudenreichii was established through a pre-screening to ensure microbial safety. During co-fermentation in wheat bran, P. freudenreichii produced a high level of vitamin B12 (ca. 183 ng/g dw on day 3). Moreover, controlling pH during fermentation could greatly enhance the vitamin B12 production (up to 332 ng/g dw on day 3). Meanwhile, L. brevis showed a strong inhibition on the propagation of Enterobacteriaceae during fermentation, as expected. The wider applicability of the established co-culture was demonstrated by fermenting 11 types of grain materials, including cereals, pseudocereals and legumes, with P. freudenreichii and L. brevis. P. freudenreichii produced a nutritionally significant level of vitamin B12 in most of the grain materials. The highest production was found in the rice bran (ca. 742 ng/g dw), followed by the buckwheat bran (ca. 631 ng/g dw), after fermentation. Meanwhile, the addition of L. brevis was able to dominate indigenous microbes during fermentation and thus greatly improve microbial safety during the fermentation of different grain materials. Overall, this thesis demonstrates that the fermentation of grain materials with P. freudenreichii and an appropriate co-culture, such as L. brevis, is a promising way to provide vitamin B12 in non-sterilized grain-based materials, without compromising microbial safety. Meanwhile, selecting raw materials that provide optimal conditions for P. freudenreichii can significantly improve the efficacy of vitamin B12 synthesis.
Source: Työväentutkimus Vuosikirja
Author: Chong Xie
Language: English
Subfield: Food Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W3048675168