Protein enrichment of cassava pulp by solid-state fermentation using Aspergillus niger

This study aimed to assess protein enrichment of sterile and non-sterile cassava pulp using four strains of Aspergillus niger -AN1, AN2, AN3, AN4.First, studies were conducted to evaluate nutritional requirements of A. niger strains and their suitability for protein enrichment of cassava pulp.Second, sterile and non-sterile cassava pulps were inoculated with spores of A. niger strains and incubated under conditions of solid-state fermentation for 8 days using standard methods.Protein contents of sterile and non-sterile cassava pulps were determined by the Kjeldahl method.Initial nutritional requirements studies showed that A. niger strains grew at rates between 2.0 cm and 8.5 cm over 10 days on potato dextrose agar medium of different pH.The dry weight of mycelia of A. niger strains varied in liquid media separately supplemented with different concentrations of thiamine, ammonium nitrate and sodium chloride.A. niger strains also showed different levels of sporulation when cultured in growth media supplemented with different concentrations of sodium chloride.Increases in protein contents of sterile cassava pulp by AN1, AN2, AN3 and AN4 were 15.65%, 22.61%, 18.30% and 19.13%, respectively.On non-sterile cassava pulp, the increases in protein content by AN1, AN2, AN3 and AN4 were 15.40%, 21.54%, 10.80% and 3.85%, respectively.A. niger strain AN2 was the most suitable strain for the enrichment of protein content of cassava because it sparsely produced spores, it had the highest mycelial growth and resulted in the greatest increase in protein content of both sterile and non-sterile cassava pulp.