Screening of glucosinolate-degrading strains and its application in improving the quality of rapeseed meal

Two myrosinase-producing fungi, Lichtheimia sp. JN3C and Aspergillus terreus, were newly isolated from decayed rapeseed meal samples obtained in Anhui Province, China. After preliminary screening, re-screening and combination of two screened strains with a yeast, an optimal composite strain to ferment rapeseed meal was obtained. Results demonstrated that the glucosinolate content of products with two molds fermentation was overall lower than that with single strain fermentation. Fermentation with composite strains containing Candida tropicalis CICIM Y0079(T) had a similar glucosinolate content, whereas the protein content was remarkably increased compared to two molds fermentation. Under sterile conditions, a 96-h fermentation with the composite strains resulted in the degradation of 66.2% of crude fiber, 28.3% of phytic acid, and 98% of total glucosinolates, which are responsible for goiter, and an increase of the protein and tannins content by 27.4 and 15.8%, respectively. In addition, glucosinolates and protein content under the non-sterile condition were not significantly different compared to the sterile condition. The fermentation greatly improved the nutritional quality of rapeseed meal by both degrading undesired substances and increasing protein content.