Dilute Acid Pretreatment, Enzymatic Saccharification, and Fermentation of Rice Hulls to Ethanol

Abstract

Rice hulls, a complex lignocellulosic material with high lignin (15.38 +/- 0.2%) and ash (18.71 +/- 0.01%) content, contain 35.62 +/- 0.12% cellulose and 11.96 +/- 0.73% hemicellulose and has the potential to serve as a low-cost feedstock for production of ethanol. Dilute H2SO4 pretreatments at varied temperature (120-190 degrees C) and enzymatic saccharification (45 degrees C, pH 5.0) were evaluated for conversion of rice hull cellulose and hemicellulose to monomeric sugars. The maximum yield of monomeric sugars from rice hulls (15%, w/v) by dilute H2SO4 (1.0%, v/v) pretreatment and enzymatic saccharification (45 degrees C, pH 5.0, 72 h) using cellulase, beta-glucosidase, xylanase, esterase, and Tween 20 was 287 +/- 3 mg/g (60% yield based on total carbohydrate content). Under this condition, no furfural and hydroxymethyl furfural were produced. The yield of ethanol per L by the mixed sugar utilizing recombinant Escherichia colistrain FBR 5 from rice hull hydrolyzate containing 43.6 +/- 3.0 g fermentable sugars (glucose, 18.2 +/- 1.4 g; xylose, 21.4 +/- 1.1 g; arabinose, 2.4 +/- 0.3 g; galactose, 1.6 +/- 0.2 g) was 18.7 +/- 0.6 g (0.43 +/- 0.02 g/g sugars obtained; 0.13 +/- 0.01 g/g rice hulls) at pH 6.5 and 35 degrees C. Detoxification of the acid- and enzyme-treated rice hull hydrolyzate by overliming (pH 10.5, 90 degrees C, 30 min) reduced the time required for maximum ethanol production (17 +/- 0.2 g from 42.0 +/- 0.7 g sugars per L) by the E. coli strain from 64 to 39 h in the case of separate hydrolysis and fermentation and increased the maximum ethanol yield (per L) from 7.1 +/- 2.3 g in 140 h to 9.1 +/- 0.7 g in 112 h in the case of simultaneous saccharification and fermentation.

Optimization of Saccharification of Biological Pre-Treated Rice Straw by Response Surface Methodology

“…The mechanism underlying the enhancement of enzymatic cellulose hydrolysis is the increase of effective cellulosic surface area as well as increase in enzyme stability by reducing thermal denaturation (Kaar and Holtzapple, 1998;Erickson et al, 2002]. For the saccharification of dilute acid pretreated rice hulls, addition of Tween 20 at 2.5g/L concentration enhanced the rice hulls saccharification by 3.5% (Saha et al, 2005). In another study, addition of Tween 80 resulted in increase in hydrolysis yield from 69 to 91% after 48 h for pretreated Lodgepole pine (Tu et al, 2009).…”

Obtención De Azúcares Fermentables a Partir De Aserrín De Pino Pretratado Secuencialmente Con Ácido-Base

“…Sin embargo, lo anterior puede ocasionar un aumento en la concentración de subproductos inhibidores del proceso fermentativo como furfural y 5-hidroximetilfurfural (Saha et al 2005, Camesasca et al 2015, Martínez et al 2015. El contenido de lignina soluble se midió en el licor resultante del PT2 debido a que la lignina se solubiliza en solución alcalina acuosa (Jagtap et al 2013).…”

Pengaruh Perlakuan Delignifikasi Terhadap Hidrolisis Selulosa Dan Produksi Etanol Dari Limbah Berlignoselulosa

“…Hal ini menjadi indikasi bahwa perlakuan delignifikasi pada dasarnya menyebabkan selulosa, yang merupakan target utama proses hidrolisis menjadi lebih mudah diakses (Harmsen 2010). Adapun penurunan kadar hemiselulosa setelah perlakuan delignifikasi mengindikasikan bahwa perlakuan delignifikasi yang diterapkan pada biomasa sengon dan pelepah sawit ini, tidak hanya menyebabkan deg radasi lignin, tetapi depolimerisasi hemiselulosa juga (Saha ., 2005 (Prentti, 2006). Perlakuan delignifikasi biomasa sengon, jika dihubungkan dengan proses hidrolisis, secara umum menyebabkan peningkatan kadar gula tereduksi dibandingkan dengan kontrol (Gambar 3).…”