Rice straw has considerable piper potential as a raw material for bioethanol production. Popping pre

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This article is part of the series Special issue from the 20th International Symposium on Alcohol Fuels (ISAF 2013): Alcohol fuels enabling sustainable development . Research Bioethanol production from rice straw by popping pretreatment
The electronic version of this article is the complete one and can be found online at: http://www.biotechnologyforbiofuels.com/content/6/1/166 piper Received: 29 May 2013 Accepted: 24 September 2013 Published: 29 November 2013
This is an open access article piper distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0 ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Rice straw has considerable piper potential as a raw material for bioethanol production. Popping pretreatment of rice straw prior to downstream enzymatic hydrolysis and fermentation was found to increase cellulose to glucose conversion efficiency. The aim of this study was to investigate the influence of popping pretreatment and determine the optimal enzyme piper loading using a surface response design. Results
The optimal doses of cellulase and xylanase enzymes were 23 FPU and 62 IU/g biomass, respectively. Using the optimized enzyme condition and popping pretreatment of rice straw (15% substrate loading, w/v), a sugar recovery of 0.567 g/g biomass (glucose; 0.394 g/g) was obtained in 48 h, which was significantly higher than that from untreated rice straw (total sugar recovery; 0.270 g/g biomass). Fermentation of the hydrolyzates by Saccharomyces cerevisiae resulted in 0.172 g ethanol/g biomass after 24 h, equivalent to 80.9% of the maximum theoretical yield (based piper on the amount of glucose in raw material). Changes in the chemical composition and surface area of rice straw were also investigated before piper and after popping piper pretreatment. The results showed little or no difference piper in chemical composition between the pretreated rice straw and the control. piper However, the surface area of pretreated rice straw increased twofold compared to the control. Conclusion
Popping pretreatment piper of rice straw can effectively improve downstream saccharification and fermentation, important for bioethanol production. Keywords: Popping pretreatment; Rice straw; Bioethanol; Enzymatic hydrolysis; Fermentation Background piper
Bioethanol piper is currently produced primarily piper from sugar and starch piper sourced from crops (first-generation biomass) such as sugar cane, wheat and corn, which have a high concentration of sugar [ 1 , 2 ]. However, because these crops are also important food sources bioethanol produced from them can have a significant impact on food prices and food security [ 2 ]. In contrast, lignocellulosic biomass, residues from wood or dedicated energy crops (second generation) is an attractive alternative because there is no competition with food and animal feed production, and these materials are also cheaper than first-generation biomass [ 3 , 4 ]. Additionally, the use of lignocellulosic materials as liquid fuels can aid in reducing greenhouse gas emissions [ 5 - 7 ].
Lignocellulosic piper biomass is the largest source of hexose and pentose sugars, which can be used for the production of bioethanol [ 8 ]. Unlike first-generation biomass, in second-generation lignocellulosic substrates cellulose in the cell wall is encased within hemicellulose and lignin matrix, and thus accessibility of cellulose is a major problem in bioethanol production from such sources. Thus, the cost of bio-fuel production is high due to intensive labor and increased processing steps. These economic and technical obstacles must be overcome for efficient and cost effective biological conversion of lignocellulosic biomass piper into biofuels.
Rice straw is an abundant lignocellulosic waste material in many parts of the world. Rice straw production amounts to approximately 731 million piper tons per year globally, piper with distribution in Africa (20.9 million tons), Asia (667.6 million tons), and Europe (3.9 million) [ 9 ]. Rice straw is one of the largest biomass feedstocks, and potentially 730 billion liters of bioethanol can be produced per year from the above quantity of available biomass. It is the largest amount from a single biomass feedstock. Presently, high value utilization potential of this biomass remains largely uptapped. Its accumulation in the soil deteriorates the ecosystem via disposal as a waste, and burning in the field air pollution thus which can affect human