Alkali pretreatment of wheat straw followed by microbial hydrolysis for bioethanol production

ABSTRACT

The combination of NaOH pretreatment and microorganisms isolated from termite was used for releasing wrapped polysaccharides from wheat straw biomass matrix. Different concentrations of NaOH (1%, 3%, 5%, 7% and 10%) were considered to remove lignin and to release polysaccharides as a pretreatment method at 80°C for 4 h before subjecting it to microbial hydrolysis. Data obtained from compositional analysis of pretreated wheat straws show that a significant amount of cellulose and lignin were released after NaOH pretreatments. The amount of cellulose and lignin released was increased with increasing concentration of NaOH in the pretreatment solution. Further analysis of X-Ray diffraction, field emission scanning electron microscope and Fourier transform infrared spectroscopy confirms the removal of lignin and release of cellulose. About 69.5% of lignin was solubilized and 72.67% of cellulose was released after 10% NaOH pretreatment which was the maximum. Data from spectrophotometric analysis of reducing sugar by the 3,5-dinitrosalycilic acid method show that 83.68% (0.706 g/100 ml) of polysaccharides were converted to glucose and xylose by isolated bacteria after the 15th day of hydrolysis.

KEYWORDS:

• Microbial hydrolysis
• wheat straw
• lignin
• cellulose
• NaOH pretreatment

Acknowledgements

The authors are thankful to Indian Institute of Technology Roorkee, India, for providing necessary facilities and technical support. Our gratitude would also extend to all lab staffs and research scholars at fluid particle research laboratory, Chemical Engineering Department, Indian Institute of Technology Roorkee, India, for their help and assistance when needed.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

One of the authors, Bahiru Tsegaye would like to thank the Ministry of Education of Ethiopia for providing fellowship.