Is it possible to identify the source of beta glucan using the Mixed Linkage β-Glucan Assay Kit (K-BGLU) kit?

Unfortunately it is impossible to differentiate between Oat, Barley and other cereal β-glucans as all of these are 1,3:1,4-β-D-glucans.

However as the structures of mushroom and fungal β-glucans are different from the cereal β-glucans it is possible to identify which type of beta glucan is present in a sample. Fungal and yeast cell walls are composed of ≤ 50% 1,3:1,6-β-glucan, whereas cereal glucans (present in oats, barley, wheat) are 1,3:1,4-β-D-glucans. 

K-YBGL (yeast and mushroom) kit measures 1,3:1,6, as well as 1,3:1,4-β-D-glucans. Cereal β-glucans can be measured using the Mixed Linkage β-Glucan Assay Kit (K-BGLU) and this value can be subtracted from the β-glucan value received with K-YBGL. 

Please note that K-BGLU measures 1,3:1,4 β-glucan and some 1,3:1,6-β-glucan as beta-glucosidase will act on the (1,3) chain until it reaches branching. We can estimate that 5-10% of 1,3:1,6 can be measured depending on the structure of beta-glucan. The yeast and mushroom samples usually do not contain 1,3:1,4 β-glucan.