Improved enzymatic hydrolysis and ethanol production by combined alkaline peroxide and ionic liquid‐water mixtures pretreatment of rice straw

Abstract

BACKGROUND Rice straw (RS), one of the most plentiful lignocellulosic wastes worldwide, has been considered a potential candidate to produce bioethanol. The object of this work was to develop an efficient and feasible pretreatment process for RS with alkaline peroxide combined with ionic liquid (IL)–water mixtures, reveal the mechanism, and achieve biomass valorization. RESULTS Alkaline peroxide pretreatment under mild conditions combined with IL–water mixtures pretreatment at a water content of 30 wt% was established, leading to a maximum lignin removal of 63.8% with an enzymolysis efficiency of 92.1% and a simultaneous saccharification and co‐fermentation efficiency of 91.0%. Furthermore, the recycled IL also showed good performance with the established pretreatment process, resulting in 251.6 g L−1 of reducing sugar and 91.9 g L−1 ethanol at high solid loading. The alkaline peroxide pretreatment enhanced lignin extraction and disrupted the RS structure to facilitate the dissolution of amorphous components by the IL–water mixtures. CONCLUSION A simple and efficient pretreatment was successfully established. The IL was successfully recycled for further pretreatments, and high concentrations of reducing sugars and ethanol were achieved using the pretreated RS. The effectiveness of the pretreatment process suggested potential application in future biorefineries. © 2018 Society of Chemical Industry

Box-Behnken design for the optimization of bioethanol production from rice straw and sugarcane bagasse by newly isolatedPichia occidentalisstrain AS.2

“…Sun et al 64 used a novel method combining Na 2 SiO 3 and a cheaper ionic liquid for the treatment of willow to obtain 39.5 g/100 g waste after enzymatic hydrolysis. Hong et al 65 used combined alkaline peroxide and ionic liquid-water mixture pretreatment of RS to obtain 251.6 g/l reducing sugar. Kaur and Kuhad 1 used combined 3% H 2 SO 4 and 4% NaOH pretreatment of RS to obtain 787 mg/g reducing sugar.…”

Pretreatment of rice straw with recycled ionic liquids by phase‐separation process for low‐cost biorefinery

“…Combinative pretreatment using alkaline peroxide and IL–water mixtures (AHP–ILW) was performed as previously described by Hong et al. [18]. In brief, the original RS was firstly soaked in 3% (w/w) H 2 O 2 solution with 15% (w/v) solid loading, and then the pH value was regulated to 11.5 by utilizing 5 mol L −1 NaOH solution.…”

“…Ethanol fermentation was conducted using Saccharomyces cerevisiae SHY07‐1, which was capable of simultaneously converting both glucose and xylose into ethanol [20]. The preparation of seed inoculum and fermentation medium was consistent with our previously described [18]. First, the pretreated RS and fermentation medium were mixed into serum bottles.…”

Combined water extraction and sodium chlorite pretreated spent mushroom compost for protease production by separate hydrolysis and fermentation and simultaneous saccharification and co-fermentation

“…The previous formula was applied to determine the crystallinity index (Lin et al 2017). Fourier transformed infrared spectroscopy (FTIR) was conducted using a spectrometer (CCR-1; Thermo Nicolet, Shanghai, China) within the wavelength range of 400 cm -1 to 4000 cm -1 , as previously described (Hong et al 2019). The protein content in water extract was determined as 6.25 multiplied by total nitrogen, which was measured by the Kjeldahl method (Elsamadony and Tawfik 2018).…”

“…The enzymatic hydrolysis was performed at 55 °C and 150 rpm for 72 h with an enzyme loading of 20 FPU/g unless otherwise specified. The released reducing sugar concentration was determined using 3,5-dinitrosalicylic acid (DNS) for the enzymolysis efficiency calculation (Hong et al 2019).…”