Nutritional and toxicological aspects of Aspergillus niger fermented cassava (Manihot esculenta, Crantz) products-based diets

Abstract

This study sought to evaluate the nutritional and toxicological potential of Aspergillus niger fermented cassava products (flour and gari). Cassava mash was fermented with pure strain of A. niger for 72 days and subsequently processed to flour and gari (the forms in which it is popularly consumed in Nigeria). Three weeks old Wistar rats were assigned into 3 groups: 1-3 such that Group 1 was fed with the basal diet (control) while Groups 2 and 3 were fed with the A. niger fermented gari- and flour-based diets (40 % inclusion) and water ad libitum for 21days. Feed intake, weight gain and feaces were monitored while haematological indices, serum enzymes and metabolites were determined at the end of the feeding experiment. The results revealed that there was no significant change (P>0.05) in the average daily feed intake, daily weight gain, feed conversion ratio, apparent and dry matter digestibility, and nitrogen intake of the rats fed A. niger fermented cassava products diet. However, there was significant increase (P<0.05) in the serum glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) activities in rats fed A. niger fermented cassava products; while there was no significant (P>0.05) change in the total bilirubin and albumin in rats fed cassava flour. Furthermore there were no significant (P>0.05) changes in the Packed Cell Volume (PCV) and White Blood Cell (WBC), while there was significant increase (P<0.05) in the Red Blood Cell (RBC). However, the A. niger fermented cassava products (flour and gari) could not be considered safe due to the elevated serum GPT and GOT which is an indication of possible damage to the liver and heart, despite the good nutritional and haematological attributes of the A. niger fermented cassava products.