Fig. 2.

Four phenotypes of FucOS were produced by Se and Le genes [41, 44]. Se and Le genes play an important role in determining the composition of FucOS [34]. FUT2 is encoded by the first gene whereas FUT3 is encoded by the second one [40–43]. According to the activation state of genes, mothers can be classified as either positive (+) or negative (−) for both genes, where 70% are Se(+)Le(+), 20% Se(−)Le(+), 9% Se(+)Le(−), and 1% Se(−)Le(−) [36, 45–47], and phenotypes to production of FucOS and main FucOS synthesized are showed