Development of a sensitive microbiological method for quantification of vitamin B12 in plant foods

Vitamin B12 has become a research topic of great interest in the face of several serious health consequences associated with VB12 deficiency, which is endemic among the rapidly increasing vegan population worldwide. VB12 is an integral cofactor in metabolism, and the deficiency of VB12 could lead to serious health conditions, including pernicious anaemia, cardiovascular disease and neurological disorders. Vegans have a high prevalence of VB12 deficiency as VB12 is found almost exclusively in animal-source foods. Several plant sources (including edible algae, tea and mushroom) have been reported to contain a relatively higher content of VB12 and could be the potential non-meat sources of VB12 for vegans. The microbiological assay based on the growth of a VB12 auxotroph bacteria, Lactobacillus leichmannii (ATCC®7830™), could be used to quantify VB12 as the bacterial growth is proportional to VB12 concentration under appropriate conditions. This study reports the optimization of a 96-well microtiter plate microbiological method capable of measuring trace levels of VB12 in different plant-based materials. The limit of detection (LOD) is 0.82pg/ml, and the limit of quantification (LOQ) is 2.58 pg/ml, both of which were superior to other methods reported in the literature. VB12 levels were found to be considerably higher in several red and green seaweed species (15.3 to 64.7 μg/100g DW) than in mushroom and tea samples (≤ 2.5μg/100g). Consumption of these seaweeds could provide a sufficient amount to meet the EU’s recommended dietary allowance of 2.4 μg/day for VB12. The developed method with demonstrated excellent performance can be used to quantify VB12 in various food commodities.