Browsing by Author "Mrema, Godwill"

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    Comparison of Escherichia Coli KO11 and Saccharomyces Cerevisiae ATCC 96581 in Fermenting Pinus Patula Hydrolysate Pretreated at Different Steam Explosion Severity
    (2012) Chacha, Nyangi; Dyrset, Nils; Mtui, Godliving; Katima, Jamidu H. Y.; Mrema, Godwill
    Bioconversion of wood residues to biofuels such as ethanol is one of the feasible initiatives towards production of renewable energy. This work compares the effectiveness of Escherichia coli KO11 and Saccharomyces cerevisiae ATCC 96581 in fermenting Pinus patula (pine) hydrolysate pretreated by acid-catalyzed steam explosion. The results show no significant difference in terms of the ethanol yield when E. coli KO11 and S. cerevisiae ATCC 96581 were used. The maximum ethanol concentration obtained in test tubes fermentation were 18.30 and 19.41 g/l for E. coli KO11 and S. cerevisiae ATCC 96581, respectively, from samples pretreated at 225°C/5 min. The ethanol yields obtained using bioreactors for samples pretreated at 225°C, 0.5% SO2, and 5 min, were 21.30 and 19.63 g/l for E. coli and S. cerevisiae, respectively. Overall, ethanol yields were higher in bioreactors than in test tubes for both strains. In comparison, S. cerevisiae consumed the substrate faster than E. coli, thus making S. cerevisiae the most preferred strain in fermentation of hydrolysates from steam pretreated P. patula.
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    Steam Pretreatment of Pine (Pinus Patula) Wood Residue for the Production of Reducing Sugars
    (2011) Chacha, Nyangi; Toven, Kai; Mtui, Godliving; Katima, Jamidu H. Y; Mrema, Godwill
    The study explores the production of reducing sugars from Pinus patula wood residual chips based on steam pretreatment technology. The severity of the steam pretreatment was altered by using two levels of temperature and time and three levels of sulphur dioxide impregnation. The results show that the efficiency of enzymatic hydrolysis depends on the severity of steam pretreatment. On a given cellulose content, the reducing sugar yield increased from 29% (15.6 g/L) under the mildest steam pretreatment conditions (180 °C, 1.5% SO2) to 91% (42.3 g/L) under the most severe steam pretreatment conditions (225 °C, 3% SO2). In all cases, the enzymatic hydrolysis yield is dependent on enzyme accessibility to the cellulose chains, as the steam pretreatment severity strongly affects biomass fragmentation.