when comparing the three natto groups, inferior quality lines had the highest average calcium
content followed by the moderate and superior lines, confirming that low seed calcium is preferred for good-quality natto.
The association between natto quality and manganese has not been thoroughly studied previously. Comparison of three natto quality lines showed large differences in the manganese means
among the three groups. Superior natto lines had significantly lower manganese content than the moderate or inferior natto quality lines. However, Mitsuboshi et al. reported that
adding Mn2+ helped B. subtilis (natto) form more spores during fermentation but current research results differ. The functionality of Mn2+ in fermentation and natto quality needs to be further
investigated.