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Sökning: WAKA:kon > Högskolan i Borås > Jeihanipour Azam

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  • Jeihanipour, Azam, et al. (författare)
  • Acid Hydrolysis of Cellulose-based Waste Textiles
  • 2011
  • Konferensbidrag (refereegranskat)abstract
    • The present study focused on conversion of cellulosic part of waste textiles into biogas and its challenges. The annual global fiber consumption exceeded 70 Mt with a cellulosic fraction of around 40%. This huge amount of fiber is further processed into apparel, home textiles and industrial products and after a certain time delay end up in waste streams. This amount of cellulose has the potential of production of approximately 20 billion liters of ethanol. Assuming a good collection and waste management system, however, there are still challenges facing the process of conversion. For instance, high crystallinity of cotton cellulose makes it hard to achieve enzymatic or bacterial hydrolysis. In addition, waste textiles are composed of different materials including natural and synthetic fibers, and the cellulosic fibers should be separated from the other materials. Furthermore, presence of dyes and reagents in the fibers can also be challenging in the bioprocessing of textile waste. In the present work, we examined the process of dilute acid hydrolysis of viscose and cotton (i.e. jeans) textiles. Hydrolyses were performed at different lengths of time (8 and 15 min), temperatures (180 and 200 °C), and acid concentrations (0.5, 1.5, and 3% w/w). Hydrolysis of viscose and jeans under identical conditions resulted in significantly different yields of glucose. This may be due to differences in the structure, i.e. high crystalline cellulose in jeans and low crystalline cellulose in viscose.
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  • Jeihanipour, Azam, et al. (författare)
  • Efficient ethanol production from spruce by N-methylmorpholine-N-oxide (NMMO) pretreatment
  • 2011
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Pretreatment of lignocelluloses with cellulose dissolution reagents is efficient and can be applied under relatively mild conditions. NMMO is an industrial cellulose solvent that can dissolve cellulose by breaking intramolecular bonds. The solvent can be recycled with over 99% recovery and does not produce toxic waste pollutants. After dissolution, the cellulose can be regenerated by fast precipitation with an anti-solvent that is usually water. The dissolution can severely modify the structure of cellulose and reduce its crystallinity, which is very important in hydrolysis of softwoods. Native species of spruce was debarked, cut, milled, and screened to achieve a size of less than 1 mm. The treatment was performed using 85%w/w NMMO solution at 120ºC for 1, 3, and 15 h. The pretreated wood species were then regenerated by addition of boiling distilled water, followed by vacuum filtration and washing. The pretreated and untreated wood species were enzymatically hydrolyzed by commercial cellulase (15 FPU/g) and β-glucosidase (30 IU/g) at 45°C for 96 h. Then, the hydrolyzates were fermented by a flocculation strain of Saccharomyces cerevisiae (CCUG 53310) at 30°C for 24 h. The results showed that the pretreatment, in general, did not significantly affect the composition of the wood, while increased the yield of hydrolysis and fermentation. The cellulose hydrolysis was increased from 11% for native spruce to more than 98% for the wood treated with NMMO for 15 h, and, correspondingly, the yield of ethanol production was increased from 8.1% to over 86.1%.
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  • Khodaverdi, Mahdi, et al. (författare)
  • Cellulase adsorption capacity and substrate reactivity of NMMO-regenerated cellulose
  • 2011
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The changes of the reactivity of cellulose during enzymatic hydrolysis and the adsorption capacity of cellulase into insoluble cellulose are two central features of several mechanistic models presented for enzymatic hydrolysis of cellulose. In the present study, these parameters were investigated for regenerated cellulose, i.e. amorphous cellulose. The regenerated pure cellulose was obtained by dissolution cotton linter in N-Methylmorpholine-N-oxide (NMMO) at 120 °C, and then regeneration by adding water. The data of adsorption of cellulase into cellulose was examined with the Langmuir isothermal model. The maximum adsorption capacity was obtained as 212, 35, and 5 mg protein/g substrate for regenerated cellulose, Avicel, and cotton, respectively. The substrate reactivity (SR) was measured while the effect of end product inhibition and also enzyme inactivation during enzymatic hydrolysis was eliminated. The SR of regenerated cellulose was declined from 1 to 0.43 after conversion of 30% of substrate in 15 min. Then, there was no significant change in the SR until conversion of 92% of cellulose which was achieved by 6 h hydrolysis. This study shows that by regeneration of cellulose its capacity of cellulase adsorption is dramatically increased. However, the effect of reactivity of cellulose on the rate of hydrolysis is eliminated and SR may be deleted from its hydrolysis kinetic model.
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