Abstract

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Production of bioethanol from pineapple waste was investigated using the solid state fermentation method. Aspergillus niger was co-cultured with Saccharomyces cerevisiae on the substrate to produce saccharification and fermentation activities respectively. The microorganisms were isolated from natural sources; soil and palm-wine respectively. Two highest cellulose-hydrolyzing strains of A. niger were selected for the study. Two strains of Saccharomyces cerevisiae were isolated from the palm-wine and identified using both colonial morphological studies and various biochemical tests. The strain that showed tolerance to 15 % ethanol concentration was selected for the bio-ethanol production study by co-culturing it with each of the two A. niger strains selected. Results of the bioethanol production showed that the fermentation process terminated at 120hr with the highest bioethanol concentration of 11.3 % (v/v) in one combination (FB6 + SC) and 7.0 % (v/v) in the second combination (SW3 + SC). The pH of the substrate dropped from 4.1 to 3.3, and the initial total soluble solids of 9.4 mg/g decreased to 3.9 mg/g at the end of fermentation. In addition, production of reducing sugars peaked at 24 hr of fermentation with 57.8 mg/g, after which it declined steadily to 16.0 mg/g at the end of fermentation. The potential shown by solid state fermentation of pineapple waste for bioethanol production indicated that it can favourably compete with submerged fermentation method commonly used for bio-ethanol fermentation. The use of A. niger isolated from natural sources produced good saccharification results, favourably competitive with that observed in commercially sold enzymes used by several workers. This may present a cheaper alternative to the commercially sold enzymes. In commercial production of bioethanol from cellulosic/lignocellulosic materials, solid state fermentation method may require smaller area of space compared to submerged fermentation method.

Keywords: Bioethanol, fermentation, pineapple waste, saccharification, solid state.