Biotechnological potential of agro-industrial wastes for protein enrichment by solid-state fermentation using Aspergillus niger

This study is to assess the biotechnological potential of agro-industrial wastes of pineapple (Ananas comosus), sweet potato (Ipomoea batatas) and watermelon (Citrullus lanatus) for protein enrichment by solid-state fermentation using Aspergillus niger. Spore suspensions of A. niger were prepared with potato dextrose broth that had been supplemented with sodium chloride, ammonium nitrate and thiamine, and adjusted to pH of 5. Initial protein contents of sterile and non-sterile wastes of the pineapple, sweet potato, and watermelon were determined by the Kjeldahl method. The remaining sterile and non-sterile wastes was inoculated with spore suspensions of A. niger and incubated at temperature of 24C under conditions of solid-state fermentation for 14 days. Protein contents of the inoculated sterile and non-sterile wastes were determined after 7 and 14 days. The sterile wastes of pineapple, sweet potato and watermelon recorded initial percentage protein contents of 4.37, 4.39, and 10.89, respectively, whereas their corresponding non-sterile wastes recorded initial percentage protein contents of 3.76, 4.00, and 10.16, respectively. The results further show that percentage increase in protein content of sterile wastes after 14 days of fermentation were pineapple, 35.01%; sweet potato, 27.60%; and watermelon, 64.40%. Percentage increase in protein content of non-sterile wastes after 14 days of fermentation were pineapple, 72.34%; sweet potato, 85.25%; and watermelon, 80.51%. These findings affirm the biotechnological potential of pineapple, sweet potato and watermelon wastes and the importance of fungi as agents for protein enrichment of agro-industrial wastes.