Investigation of effects of different cassava cultivars with respect to hydrogen cyanide content on their starch hydrolysis

The effects of Hydrogen Cyanide (HCN) contents of different cultivars of cassava on the kinetic and extent of hydrolysis were studied. The results obtained showed that between 75 and 80% of HCN content had been lost during processing. Starches from cultivars with different HCN contents, Iditeru White-leaves 70.2 mg/kg, Iditeru Red-leaves 46.4 mg/kg and 920057 34.6 mg/kg, representing bitter, intermediate and sweet cultivars, respectively, were enzymatically hydrolyzed into reducing sugars. Conversion of starch to reducing sugars reached 246.2 g/L for Iditeru white-leaves, 267.9 g/L for Iditeru red-leaves and 262.2 g/L for 920057 with corresponding Dextrose Equivalent (DE) of 82.1, 89.3 and 87.4%, respectively. Statistical analysis showed that there was no significant difference (p > 0.05) in the amount of reducing sugars released in the cassava starch hydrolysates (CSH) and the % DE obtained. After 24 hr of cultivation of Saccharomyces cerevisiae on the CSH as the sole carbon source for the production of baker’s yeast on a bench scale bioreactor, the microorganism was able to utilize 80 and 81% of the sugars present in the CSH of Iditeru-white leaves and 920057 cultivars, respectively. Maximum baker’s yeast production of 8.8 and 9.1 g/L were obtained for Iditeru-white leaves and 920057 cultivars, respectively. Statistical analysis showed that there was no significant difference (p > 0.05) in the amount of reducing sugars consumed in the CSH as well as the baker’s yeast produced. Hence, HCN contents of different cultivars of cassava had no significant effect on both the rate and extent of hydrolysis. Also, the HCN contents did not affect the performance of the microorganism employed in this work.Keywords: Cassava, starch, cultivars, hydrogen cyanide, hydrolysi

Production of biodiesel from crude neem oil feedstock and its emissions from internal combustion engines

This study investigates biodiesel production using crude neem oil having high acid value, as a feedstock. The effects of some operating variables were ascertained and its combustion performance was assessed in an internal combustion engine. Due to its high acid value, the neem oil was processed via two step acid – base transesterification process. The first step reduced the acid level to <2 mgKOH/g while the second step involved direct conversion to fatty acid methyl ester using 1% NaOH as catalyst. The lowest viscosity value was used as a proxy measure to determine the extent of the reaction. The results reveal the optimum conditions for biodiesel production to be ratio 1:6 of oil to methanol and 1.5 h reaction time. The viscosity at this condition was 5.53 cSt. The same procedure was repeated for NaOCH3 catalyst concentrations of 0.5, 0.75, 1 and 1.25%. The lowest viscosity of 6.79 cSt was recorded at both 1 and 1.25% catalyst concentrations. The fuel properties of the biodiesel compared favorably with the recommendation by the American Standard Testing Method. The emissions of different blends showed that neem biodiesel has lower emissions of CO and NO than petrol diesel but higher NOX. Thus, neem oil as non-edible oil can be a good renewable raw material for biodiesel production.Key words: Neem, biodiesel, internal combustion, transesterification, free fatty acid

Optimization of Process Variables for the Production of Oxalic Acid from Sweet Potato Starch Hydrolyzate.

In this study optimization of oxalic acid production from Sweet Potato Starch Hydrolyzate (SPSH) using Aspergillus niger was investigated. The effects of three independent variables (concentrations of SPSH, fermentation time and pH) on the response (oxalic acid yield) and their reciprocal interactions were established using Response Surface Methodology (RSM). The box behnken design (BBD) was used to generate a total of 17 fermentation runs, which were subsequently conducted. A second-order mathematical model was obtained to predict the oxalic acid yield. A statistical model predicted the highest conversion yield of oxalic acid to be 103.274 g/l, at the optimal condition of SPSH of 149.97 g /l, time of 9 days, and pH of 6. The optimized condition was validated with the actual oxalic acid yield of 103.26 g/l. This work revealed that sweet potato starch could serve as alternative carbon source for oxalic acid production and the results could be scaled up to industrial production. Keywords: Sweet potato, Response Surface Methodology, Oxalic acid, Optimization, Aspergillus niger

Production of Recombinant Glucosyltransferase S in Escherichia coli with and without coproduction of molecular chaperones

No Abstract.Nigerian Journal of Genetics Vol. 20 2006: pp. 26-3

Production of biodiesel by transesterification of refined soybean oil

This study focused on the production of biodiesel via transesterification of refined soybean oil obtained locally. Sodium hydroxide was used as the alkali catalyst and methanol (as alcohol) was used in the transesterification process due to its low cost. The methanol-to-oil molar ratio was maintained at 6:1. The effect of reaction temperature with time and the catalyst loading were studied. The reaction temperature and the catalyst loading were varied at 30, 40, 50, 60 and 70 oC; and at 0.5 and 1.0% weight of oil, respectively. After transesterification of the soybean oil, the fatty acid methyl esters [FAMEs (biodiesel)] conversion was found to rise with an increase in the catalyst loading and also with the reaction temperature but no significant difference (P > 0.05) was found between the temperatures of 60 oC and 70 oC. The optimum methyl esters conversion of 97.89% was achieved at 60 oC for 3 h with 1% (w/w) catalyst. The viscosity (at 40 oC), density, cloud point, pour point, flash point and acid number were 3.40 cSt, 0.86 g/ml, -1 oC, -7 oC, 175 oC and 0.19, respectively. This optimum methyl esters conversion obtained met ASTM standard of D-6751. Therefore, soybean oil has been shown in this study as a good candidate for biodiesel production and the data acquired can be scaled up for large scale production. © 2010 International Formulae Group. All rights reserved. Keywords: Renewable energy, fatty acid methyl esters, diesel, catalyst