Solid-state fermentation of rapeseed meal using Schizochytrium ATCC 20888 to improve docosahexaenoic acid and degradate toxin

Rapeseed meal (RM), as one of the common plant-derived feed ingredients, is regarded as high production but low utilization rate. To enhance the nutritional value of RM and reduce the shortage of feed ingredients, solidstate fermentation (SSF) of RM was employed using Schizochytrium ATCC 20888 in this study. A combination of single-factor experiments and orthogonal experiments were performed to explore the optimal substrate for SSF with Schizochytrium ATCC 20888 and its impact on the surface structure, nutrients, and toxin removal rate of RM. The results indicated that the optimal substrate for SSF of RM was achieved by adding 10% glucose, 5% cornmeal, 1.8% sea salt, and maintaining a material/water ratio of 1.4:1. Under this condition, the solid-fermented RM with Schizochytrium ATCC 20888 exhibited a notable adherence of microbial cells on its surface as well as a obvious roughened texture, the emergence of porous, and loose structures. The concentrations of polypeptide and total free amino acids increased by 47.0% and 71.63%, respectively. The alkanoic acid content decreased significantly while the content of long-chain unsaturated fatty acids increased notably, especially for oleic acid (48.45%) and docosahexaenoic acid (DHA) (1.85%). The removal rates of glucosinolates, oxazolidinethione (OZT), and isothiocyanates (ITC) reached up to a maximum of 61.36%, 43.68%, and 55.47%, respectively. Our finding clearly confirm that SSF of RM with Schizochytrium ATCC 20888 can effectively modify the structure of RM, and improve its nutritional value, and reduce toxin content, thereby providing new insight into the further development of RM as feed ingredients.