an official journal of: published by:
Editor in Chief: RAFFAELLO COSSU


  • Karamjeet Kaur - The Ohio State University, United States
  • Urmila Gupta Phutela - Punjab Agricultural University, India


Released under CC BY-NC-ND

Copyright: © 2018 Cisa Publisher


Paddy straw is a lignocellulosic waste rich in holocellulose (cellulose+hemicellulose) content. It can be used as a good substrate for biogas, bioethanol and biodiesel production. However, the recalcitrant cell wall components i.e. lignin and silica are the main deterrent to efficient utilization of paddy straw. This stringent sheath of lignin and silica does not allow fermenting microbes to access holocellulose. Pretreatment of paddy straw is, therefore, crucial to get rid of lignin and silica. In this context, paddy straw was pretreated with various alkalis viz. NH3, Na2SO3, Na2CO3 and NaOH in the current study. All the alkali pretreatments were supplemented with microwave irradiations (720 W, 18°C) for 30 minutes. Paddy straw was also pretreated microbially with Pleurotus florida for 15 days via spawning. Morphological and structural changes in the pretreated paddy straw were visualized via Scanning Electron Microscopy (SEM). The straw turned remarkably fragile with enhanced bulk density and surface wettability after 4% NaOH-30 min microwave pretreatment. The pretreated straw was also found to lack silicified cuticle layer and lignin sheath which exposes straw sugars (cellulose and hemicellulose) to fermenting microbes.


Editorial History

  • Received: 08 Mar 2018
  • Revised: 13 Jun 2018
  • Accepted: 11 Jun 2018
  • Available online: 06 Aug 2018


Alizadeh H., Teymouri F., Gilbert T.I. and Dale B.E. (2005). Pretreatment of switchgrass by ammonia fiber explosion (AFEX). Appl Biochem Biotechnol 121(1-3): 1133-1141.

Bae H.D., McAllister T.A., Kokko E.G., Leggett F.L., Yanke L.J., Jakober K.D., Ha J.K., Shin H.T. and Cheng K.J. (1997). Effect of silica on colonization of rice straw by ruminal bacteria. Anim Feed Sci Technol 85: 165-181.

Chesson A. (1981). Effects of sodium hydroxide on cereal straws in relation to the enhanced degradation of structural polysaccharides by rumen microorganisms. J Sci Food Agric 32: 745-758.

Chundawat S.P.S., Venkatesh B. and Dale B.E. (2007). Effect of particle size based separation of milled corn stover on AFEX pretreatment and enzymatic digestibility. Biotechnol Bioeng 96: 219-231.

Cianchetta S., Maggio B.D., Burzi P.L. and Galletti S. (2014). Evaluation of selected white-rot fungal isolates for improving the sugar yield from wheat straw. Appl Biochem Biotechnol 173: 609-623.

Delgenes J.P., Penaud V. and Moletta R. (2002). Pretreatments for the enhancement of anaerobic digestion of solid wastes In: Biomethanization of the organic fraction of municipal solid wastes. pp. 201-28, IWA Publishing.

Fan L.T., Lee Y.H. and Gharpuray M.M. (1982). The nature of lignocellulosics and their pretreatments for enzymatic hydrolysis. Adv Biochem Eng 23: 157-187.

Fengel D. and Wegener G. (1984). Wood: chemistry, ultrastructure, reactions. De Gruyter, Berlin, New York.

Gadde B., Menke C. and Wassmann R. (2009). Rice straw as a renewable energy source in India, Thailand and Philippines: Overall potential and limitations for energy contribution and green-house gas mitigation. Biomass Bioener 33(2): 1532-1546.

Gregg D and Saddler JN (1996) A techno-economic assessment of the pretreatment and fractionation steps of a biomass to ethanol process. Appl Biochem Biotechnol 57-58: 711-727.

Harbers L.H., Kretner G.L. and Davis G.V. (1982). Ruminal digestion of ammonium hydroxide treated wheat straw observed by scanning electron microscopy. J Anim Sci 54:1309-1319.

Hendriks A.T.W.M. and Zeeman G. (2009). Pretreatments to enhance the digestibility of lignocellulosic biomass. Bioresour Technol 100: 10-18.

Jan P. and Alexandra P. (2006). Process of removing silica from cellulosic material. U.S. Patent, 20060225852.

Karunanandaa K., Varga G.A., Akin D.E., Rigsby L.L. and Royse D.J. (1995). Botanical fractions of rice straw colonized by white-rot fungi: Changes in chemical composition and structure. Anim Feed Sci Technol 55:179–99.

Kaur K. and Phutela U.G. (2014). Improving paddy straw digestibility and biogas production through chemical-microwave pretreatments. Agric Sci Digest 34 (1): 8-14.

Kaur K. and Phutela U.G. (2016). Sodium carbonate pretreatment: An approach towards desilication of paddy straw and enhancement in biogas production. Paddy Water Environ. 14 (1): 113-121.

Kaur K. and Phutela U.G. (2016a). Enhancement of paddy straw digestibility and biogas production by sodium hydroxide-microwave pretreatment. Ren. Energy 92: 178-184.

Kirk T.K. (1984). In: Nicholas DD (Ed.) Wood determination and its prevention by preservative treatments, University Press, New York Syracuse, pp. 149-181.

Lam T.B.T., Iiyama K. and Stone B.A. (1992). Cinnamic acid bridges between cell wall polymers in wheat and phalaris internodes. Phytochem 31: 1179-1183.

Liu C. and Wyman C.E. (2003). The effect of flow rate of compressed hot water on xylan, lignin and total mass removal from corn stover. Ind Eng Chem Res 42: 5409-5416.

Liu C.G. and Wyman C.E. (2005). Partial flow of compressed hot water through corn stover to enhance hemicellulose sugar recovery and enzymatic digestibility of cellulose. Bioresour Technol 96(18): 1978-1985.

Newnham R.E., Jang S.J., Xu M. and Jones F. (1991). Fundamental interaction mechanisms between microwaves and matter. In: Clark DE, Gac FD and Sutton WH (Eds.) Microwaves: Theory and Application in Materials Processing (Ceramic Transactions), vol. 21, America Ceramic Society, Westerville, Ohio, USA.

Park S.Y., Keiichi K., Yuji M., Gyosuke M. and Kenji I. (1999). Kinetic comparison between delignification and silica removal during alkaline pulping of rice straw. Jpn TAPPI J 53(11): 1492-1499.

Park S.Y., Koda K., Matsumoto Y., Meshitsuka G. and Iiyama K. (2000). Oxygen weak base pulping of rice straw with minimum silica removal. Jpn TAPPI J 54(9): 1245-1251.

Pavlostathis S.G. and Gossett J.M. (1985). Alkaline treatment of wheat straw for increasing anaerobic biodegradability. Biotechnol Bioeng 27: 334-344.

Pettersen R.C. (1984). The chemical composition of wood. In: Rowell R M (ed) The chemistry of solid wood, Advances in Chemistry Series, Vol. 207, pp.984, American Chemical Society, Washington, DC.

Phutela U.G., Kaur K., Gangwar M. and Khullar N.K. (2012). Effect of Pleurotus florida on paddy straw digestibility and biogas production. Int J Life Sci 6 (1): 14-19.

Ramos L.P. (2003). The chemistry involved in the steam treatment of lignocellulosic materials. Quim Nova 26(6): 863-871.

Sarkar N. and Aikat K. (2012). Alkali pretreatment of rice straw and enhanced cellulose production by locally isolated fungus Aspergillus fumigatus NITDGPKA3. J Microbiol Biotechnol Res 2(5): 717-726.

Shevchenko S.M., Beatson R.P. and Saddler J.N. (1999). The nature of lignin from steam explosion/enzymatic hydrolysis of soft wood. Appl Biochem Biotechnol 77-79: 867-876.

Sun R.C. (2010). Cereal straw as a resource for sustainable biomaterials and biofuels, Elsevier, Amsterdam, The Netherlands.

Taha M., Shahsavari E., Al-Hothaly K., Mouradov A., Smith A.T., Ball A.S. and Adetutu E.M. (2015). Enhanced biological straw saccharification through co-culturing of lignocellulose degrading microorganisms. Appl Biochem Biotechnol 175: 3709–3728.

Teymouri F., Laureano-Perez L., Alizadeh H. and Dale B.E. (2005). Optimization of the ammonia fiber explosion (AFEX) treatment parameters for the enzymatic hydrolysis of corn stover. Bioresour Technol 96: 2014-2018.

Thiex N.J.W. (2000). Animal feed. In: Official methods of analysis, 17th edn. Association of Official Analytical Chemists (AOAC), Gaithersburg.

Van Soest P.J. (2006). Rice straw, the role of silica and treatments to improve quality. Anim Feed Sci Technol 130(3-4): 137-171.

Van Soest P.J. (1963). Use of detergents in the analysis of fibrous feeds. II. A rapid method for the determination of fiber and lignin. J Assoc Official Anal Chemists. 46: 829-835.

Wang J.K., Liu J.X., Li J.Y., Wu Y.M. and Ye J.A. (2007). Histological and rumen degradation changes of rice straw stem epidermis as influenced by chemical pretreatment. Anim Feed Sci Technol 136(1-2): 51-62.

Ward G., Hadar Y. and Dosoretz C.G. (2004). The biodegradation of lignocellulose by white-rot fungi. In: Arora DK and Dekker M (Eds.) Fungal Biotechnology in Agricultural, Food and Environmental Applications, New York, pp. 393-407.

Zhu S.D., Huang W.J., Huang W.X., Wang K., Chen Q.M. and Wu Y.X. (2015). Pretreatment of rice straw for ethanol production by a two-step process using dilute sulfuric acid and sulfomethylation reagent. Appl. Energy 154: 190–196.