Abstract-

The study aimed at exploring the suitability of processing residues from selected root and vegetables for bioethanol production, which are otherwise environmental pollutants. The effect of lime pretreatment at high (HT), low (LT) or room (RT) temperatures on compositional and ultrastructural changes in peels of root crops (sweet potato, elephant foot yam and tannia) and vegetable processing residues (peels from ash gourd and mixed vegetable waste) was studied. Pretreatment resulted in the removal of very little polysaccharides, including starch from these biomasses. Hemicellulose was removed to a higher extent in 24 h RT pretreatment (11.6-12.3%) compared to 7.3-8.5% removal in HT pretreatment. Maximum lignin removal (ca. 33-38%) occurred in RT pretreated (24 h) samples. Approximately 22-25.7% lignin was removed during HT pretreatment (121 °C) for 30 min. which increased to 28-31% when prolonged to 60 min. Pretreatment Efficiency (PE) was low (4.2-14.7%) in HT pretreatment, while 5.7-13.5% and 5.2-14.2% PE was observed in LT and RT pretreatments respectively. Scanning electron micrographs of lime pretreated biomass indicated that starch being a major ingredient of the biomass under study, preferential saccharification of starch by amylases might be necessary to expose the cellulose and hemicellulose for their subsequent saccharification to release fermentable sugars.