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Wheat Straw Bio-refining Part II: Optimization of Alkali Pre-treatment Method with Microwave Radiation for Fermentable Sugars Separation

[ Vol. 4 , Issue. 4 ]

Author(s):

Onome Festus , Vasiliki K. Skoulou and Sharif H. Zein *   Pages 306 - 316 ( 11 )

Abstract:


Background: The potential of microwave-assisted heating for enhancing the alkaline pretreatment of lignocellulosic waste is highlighted in this work.

Objective: To maximize separation of fermentable sugars from wheat straw.

Methods: Wheat straw hydrolysis assisted by microwave was carried out by setting up a statistical experimental design method and further investigating the main process parameters, namely: temperature (°C), microwave power (W), NaOH concentration (M) and wheat straw pre-treatment time (min) towards maximization of fermentable sugars extraction from wheat straw. The reducing sugars yield (response) of the alkaline pre-treated and microwaved wheat straw in lab scale provided data for building a predictive model which reflected interactions, significance and impact of the process parameters (factors) on the wheat straw hydrolysis yield.

Results: SEM and FTIR images of untreated and alkaline pre-treated wheat straw were studied for investigating the morphological changes of wheat straw surface quality and structure resulting from the microwave and/or alkaline pre-treatment. In addition reducing sugars yield of 87%wt. from wheat straw pre-treated at 180°C, 550W microwave power, 0.65M of NaOH for 25min was achieved. This result was significantly higher compared to the one from the straw which was only hydrolysed enzymatically (30 %wt).

Conclusion: It was found that shorter pre-treatment times were obtained at higher temperatures, alkali concentration and moderate microwave power levels. The results obtained were further optimized and indicated that the microwave-assisted alkaline pre-treatment of wheat straw technique is an attractive pre-treatment method which reduces the wheat straw pre-treatment time and enhances the hydrolysis yield.

Keywords:

Bioethanol, enzymatic hydrolysis, experimental design, fermentable sugars, lignocellulose, microwave-assisted pre-treatment, wheat straw.

Affiliation:

Chemical Engineering, Faculty of Science and Engineering, School of Engineering and Computer Science, University of Hull (UoH), Kingston Upon Hull, HU6 7RX, Chemical Engineering, Faculty of Science and Engineering, School of Engineering and Computer Science, University of Hull (UoH), Kingston Upon Hull, HU6 7RX, Chemical Engineering, Faculty of Science and Engineering, School of Engineering and Computer Science, University of Hull (UoH), Kingston Upon Hull, HU6 7RX

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