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The kinetics of gluconic acid production by Aspergillus niger (A. niger) using breadfruit hydrolysate was studied in a batch bioreactor. A simple model of Luedeking-Piret, logistic, and Luedeking-Piret-like equations were proposed for gluconic acid production, cell growth, and breadfruit hydrolysate consumption respectively. The maximum gluconic acid concentration (Pt) of 109.95 g/L with 0.967 g/g process yield (88.70%) was obtained for the medium containing 120 g/l breadfruit hydrolysate at 2 vvm aeration rate. For the same conditions, the biomass concentration and maximum specific growth were obtained as 24.3 g/L and 0.018 hr 21 respectively. The models proposed for the gluconic acid production was sufficiently satisfactory, since the theoretical values of Pt (100.94 g/L) and biomass concentration (23.43 g/L) obtained from the models were almost the same with the experimental values. The model for the breadfruit hydrolysate utilization gave R 2 and Adj. R 2 of above 0.840 and 0.660 respectively; an indication that the model is suitable for the production of gluconic acid. Therefore, the concentration of initial breadfruit hydrolysate as substrate and aeration rate have shown significant effect on gluconic acid production and A. niger accumulation. The evaluation of the models showed that the gluconic acid production was growth-associated. Practical applicationsBreadfruits, a perishable fruit has been abundantly found in Ile-Ife, Nigeria where 50% of it perishes due to its short shelf-life. This study therefore provides alternative use for breadfruit, in order to reduce its wastage. Furthermore, the growing demand of gluconic acid can be met through the use of this cheap and available breadfruit. The findings in this study can be employed to develop a bioreactor for fermentation of breadfruit hydrolysate to produce gluconic acid. K E Y W O R D SAspergillus niger, breadfruit, fermentation, gluconic acid, hydrolysis

Indexing p. 1  Editorial Bord p. 1  Guide for Authors p. 3  Manuscript preparation p. 5

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This study investigates physical and chemical properties two seeds namely Ugba (Telfairia pedata) and Ugwu (Telfairia occidentalis) using soaking soxhlet methods of extraction. The physical properties examined are moisture content, ash content, crude protein, fat and oil, crude fibre and carbohydrates. The chemical properties examined are Acid value (mgKOH/g), saponification value, iodine value, free fatty acid, peroxide and refractive index. Higher mean values of moisture content, ash content, crude fibre and carbohydrates were noticed in Ugwu than in Ugba under soaking method. However, the trend was reversed for crude protein and free fatty acid, in whose case they appear to be higher in Ugba than in Ugwu. For soxhlet method, moisture content, ash content, crude fibre and carbohydrates seems to have higher mean values in Ugwu seed compared to when Ugba seed was used. However, crude protein and fat and oil content were higher using Ugba seed than Ugwu seed oil. For soaking method, Ugba seed seem to produce higher mean values of sap value, iodine value, and refractive index when compared with Ugwu seed. On the other Ugwu, seems to produce acid value, free fatty acid and peroxide value when compared with ugba for soaking method. Using soxhlet apparatus however, Ugba seed produces higher mean values for acid value, sap value, iodine value, and free fatty acid compared to Ugwu. The reverse was the case with peroxide and refractive index, still with soxhlet apparatus.Kathmandu University Journal of Science, Engineering and TechnologyVol. 13, No. 2, 2017, page: 48-60