Biochemical composition, heavy metal content and their geographic variations of the form species Nostoc commune across China

Nostoc commune is a form species. It has been used as a food and herbal medicine for a long time. This study investigated the biochemical composition, heavy metal content and their geographic variations of the N. commune colonies, which were sampled from all the main production areas throughout the mainland China. N. commune from different areas in China had significant variations in biochemical composition and heavy metal contents. The dry mass of N.commune is mainly composed of carbonate rather than protein. Compared to Nostoc sphaeroides and wheat, N. commune contains low protein,but has higher dietary fibre content. Meanwhile, it has a higher content of Ca and Fe minerals.There were significant features in the biochemical composition and heavy metal content with latitude in China. With the increasing latitude, ash content and lead generally tended to increase, while carbohydrate content tended to decrease. All the samples are polluted by the heavy metals lead, chromium and arsenic, and now all of them are not safe enough for food unless these heavy metals are removed. If the heavy metals Pb, Cr and As are removed, N.commune can be good resources of carbonate and protein to human being and animals.