Production of bioethanol from biodegraded alkali pretreated rice straw

Abstract

NaOH (1%) treated paddy straw was neutralized for pH with 10% HCl. The result of pre-treatment on straw was examined by Fourier-transform infrared spectroscopy (FTIR) analysis. FTIR spectra revealed the degradation of straw cellulose and lignin. The broadband observation 3421 of untreated and 3411 cm−1 of pre-treated straw shows O–H stretching hydrogen bond, 2920 is C–H stretching showing changes during NaOH pre-treatment. Similarly peaks around 1600 cm−1 is assigned to lignin and this peak was reduced in pretreated straw. The pre-treated straw was further biodegraded by inoculation of Trichoderma reesei (treatments were; T1—pre-treated straw + T. reesei, T2—rice + T. reesei, T3—straw, T4—sterilized straw + T. reesei, T5—pre-treated sterilized straw + T. reesei). Results revealed that best treatment was T5 followed by T2 and T4. In case of treatment T5 i.e. pre-treated sterilized straw + T. reesei the FTIR graphs was approximately flat showing a complete degradation of paddy straw. Peaks from 2400 to 900 cm−1 were missing in treatment T5 whereas rest of the peaks for lignin (1600–1515 cm−1), Hemicelluluse (2400 cm−1) and cellulose (3400–3020 cm−1, 1215–1025 cm−1) were present in other treatments. To detect bioethanol production Saccharomyces cerevisiae was inoculated into treatment T4 and T5. The ethanol production was confirmed by GC–MS in treated and untreated straw after yeast inoculation.