Degradation of pyrimidine glycosides and L-DOPA in the faba bean by Rhizopus oligosporus

Faba bean is an excellent source of nutrients, however, it contains some undesired compounds which still remain a concern. The aim of this study was to investigate the possibility of reducing the content of L-DOPA and pyrimidine glycosides by applying fermentation using three strains of Rhizopus oligosporus namely ATCC 48012, ATCC 42222 and ATCC 22959. The formation of potentially harmful degradation products during fermentation in the model conditions was also monitored. Results show that all investigated strains caused a significant decrease in the content of these compounds. A complete L-DOPA degradation was achieved within 2 days. In the case of vicine and convicine, a significant reduction was observed after 6 days, by 91 and 98%, respectively. Moreover, the LC-MS analysis allowed to detect carboxysalsolinol, divicine, and isouramil, as degradation products created during fermentation. This is the first report, where fermentation by Rhizopus oligosporus was applied in order to improve faba beans' nutritional value, by decreasing L-DOPA and pyrimidine glycosides.