Total utilization of different parts of wild cocoyam in production of sugar feedstock for bioethanol production; An integrated approach

This study investigated production of bioethanol from wastes of different parts of wild cocoyam plant. Cocoyam peels, leaves and stalks were hydrolysed using amylase and cellulase from Aspergillus niger isolated from cocoyam compost. Proximate analysis of substrates was evaluated. Culture pH, inoculum concentration and nitrogen sources were optimized. Total carbohydrate contents (%) were: peel (85.94 ± 0.014), leaves (64.80 ± 0.012) and stalks (73.88 ± 0.014). Reducing sugar concentration (mg/mL) of 11.99, 7.89 and 4.46 were observed for tuber peels, stalks and leaves, respectively. Optimum culture conditions were obtained at pH 5, carbon concentration of 5% (peel, stalk) and 4% (leaf). Soya bean meal was the best nitrogen source for peel and stalk, whilst yeast extract best for leaf. Inoculum concentrations of 2% and 5% were best for the peel and the stalk respectively. Cocoyam leaves gave highest ethanol yield of 0.38%, the peels, 0.21%, and combined substrates, 0.28%. [Display omitted] •Aspergillus niger secreted enzymes able to utilize parts of the wild cocoyam plant.•Hydrolysis of cocoyam peels, stalks and leaves did not require pre-treatment.•Time, pH, inoculum, carbon and nitrogen sources influenced reducing sugar yield.•Highest bioethanol yield was from cocoyam leaves.•Multiple ethanol yield was obtained from a mixture of the substrate.