Characteristics of Corn Stover Pretreated with Liquid Hot Water and Fed-Batch Semi-Simultaneous Saccharifi cation and Fermentation for Bioethanol Production

Abstract

Background: Previous research on alkaline pretreatment has mainly focused on optimization of the process parameters to improve substrate digestibility. To achieve satisfactory sugar yield, extremely high chemical loading and enzyme dosages were typically used. Relatively little attention has been paid to reduction of chemical consumption and process waste management, which has proven to be an indispensable component of the biorefineries. To indicate alkali strength, both alkali concentration in pretreatment solution (g alkali/g pretreatment liquor or g alkali/L pretreatment liquor) and alkali loading based on biomass solids (g alkali/g dry biomass) have been widely used. The dual approaches make it difficult to compare the chemical consumption in different process scenarios while evaluating the cost effectiveness of this pretreatment technology. The current work addresses these issues through pretreatment of corn stover at various combinations of pretreatment conditions. Enzymatic hydrolysis with different enzyme blends was subsequently performed to identify the effects of pretreatment parameters on substrate digestibility as well as process operational and capital costs. Results: The results showed that sodium hydroxide loading is the most dominant variable for enzymatic digestibility. To reach 70% glucan conversion while avoiding extensive degradation of hemicellulose, approximately 0.08 g NaOH/g corn stover was required. It was also concluded that alkali loading based on total solids (g NaOH/g dry biomass) governs the pretreatment efficiency. Supplementing cellulase with accessory enzymes such as α-arabinofuranosidase and β-xylosidase significantly improved the conversion of the hemicellulose by 6-17%.

Pre-treatment of sugarcane bagasse with a combination of sodium hydroxide and lime for improving the ruminal degradability: optimization of process parameters using response surface methodology

“…hemicellulose, cellulose and lignin), the cellulosic fraction was not significantly affected by pre-treatment with alkali, whereas hemicellulose was significantly solubilized. In a recent study, where corn stover was pretreated with NaOH to increase its enzymatic hydrolysis, more than 95% of the cellulosic fraction was preserved (Chen et al 2013); it was also shown that when NaOH loading increased from 0.04 to 0.1 g/g corn stover, degradation of hemicellulose (xylan) was increased by 20%. Rezende et al (2011) pre-treated SCB with various loadings of NaOH to enhance its enzymatic digestibility; in general, compositional analysis of SCB pre-treated by various loading of NaOH showed that alkaline pretreatment resulted in a significant increase in hemicellulose and lignin solubilization, whereas cellulosic fraction was well preserved and its concentration increased in retained solids.…”

“…Alkaline pre-treatment (using either lime or sodium hydroxide, or combination of them) for enhancing either ruminal digestibility or enzymatic digestibility in cellulosic-ethanol production process has been widely attempted (Haddad et al 1998;Xu & Cheng 2011;Ahmadi et al 2013;Chen et al 2013). For example, combination of sodium hydroxide and lime to enhance the enzymatic hydrolysis in lignocellulosic-ethanol production process was reported by Xu and Cheng (2011) in which, at the recommended conditions [6 h, 21°C, 1.0% (w/w) NaOH, and 0.2% (w/w) Ca(OH) 2 ], the glucose and xylose yields of switchgrass reached 59.4% and 57.3% of their theoretical yields, respectively.…”

Düşük Sicaklik Düşük Zaman Alkali̇ Ön İşlemleri̇ni̇n Findik Kabuğunun Bi̇leşi̇mi̇ Ve Enzi̇mati̇k Hi̇droli̇zi̇ Üzeri̇ne Etki̇si̇ni̇n İncelenmesi̇

“…Kang ve arkadaşları kolza atıkları ile yapmış oldukları çalışmada 55ºC gibi düşük sıcaklıklarda alkali derişiminin ve ön işlem süresinin etkisi olmadığını, ancak ön işlem süresinin yüksek alkali derişiminde etkili olduğunu ve düşük ön işlem süresinin enzimatik hidroliz üzerine etkin olmadığını bildirmişlerdir [33]. Alkali derişiminin lignin giderimi kadar hemiselüloz giderimi (çözünmesi/hidroliz olması) üzerine de etkili olduğu bilinmektedir [34]. Bu çalışmada, NaOH derişiminin %0,5 olduğu durumda çok düşük olan hemiselüloz gideriminin, alkali derişiminin %2,25'e yükseltilmesiyle anlamlı bir şekilde arttığı görülmektedir (Şekil 4).…”

Combined sodium hydroxide and ammonium hydroxide pretreatment of post-biogas digestion dairy manure fiber for cost effective cellulosic bioethanol production

“…We studied the effects of different pretreatment parameters, including alkali loading, temperature, and residence time, on the recovery and subsequent enzymatic digestion of PBD manure fiber ( Table 2). We used low-severity protocols to evaluate pretreatment under conditions that minimized the cost of chemicals and the energy needed to heat the samples: 100°C for 5 min at concentrations of 2 − 10% (by dry fiber weight) of NaOH and NH 3 [41,58]. These pretreatment protocols led to substantial decreases in fiber residual lignin (16 − 40% delignification) and improved carbohydrate recovery (80-67%) and higher carbohydrate concentration (2-10%).…”

“…Alkaline biomass pretreatment methods using either sodium hydroxide [40,41] or aqueous ammonia [42] have been studied in recent years and shown to have high efficiency and low cost [14,38]. Sodium hydroxide treatment effectively depolymerizes and removes the most labile biomass components, such as hemicelluloses and lignin, causes swelling that increases enzyme accessible surface area (for solvation and saponification reactions) and reduces the degree of polymerization and crystallinity of cellulose [40]. Aqueous ammonia reacts selectively with lignin by cleaving C-O-C bonds in lignin and ether and ester bonds in lignincarbohydrate complexes, but carbohydrate removal and/ or degradation is limited.…”