Understanding of alkaline pretreatment parameters for corn stover enzymatic saccharification

Abstract

BackgroundPrevious 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 bio-refineries. 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.ResultsThe 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%.ConclusionsThe current work presents the impact of alkaline pretreatment parameters on the enzymatic hydrolysis of corn stover as well as the process operational and capital investment costs. The high chemical consumption for alkaline pretreatment technology indicates that the main challenge for commercialization is chemical recovery. However, repurposing or co-locating a biorefinery with a paper mill would be advantageous from an economic point of view.

Microbial inhibitors: formation and effects on acetone-butanol-ethanol fermentation of lignocellulosic biomass

“…A high SF led to substantial loss of hemicellulose, facilitated degradation of hexose and pentose sugars to weak acids and furan derivatives (Chen et al 2013b). Baral et al (2014) reviewed the effects of SF on sugar production and corresponding inhibitor formation for the most common pretreatment processes, specifically with corn stover as a substrate.…”

“…Therefore, determining the optimum particle size can yield more sugars and, subsequently, reduce inhibitors as well as preparation costs. Researchers have used 0.5-25 mm particle sizes for corn cobs and stover (Chen et al 2013b;Gao et al 2012;Liu et al 2013a;Mu et al 2011;Qin et al 2012;SU Donghai et al 2006;Um and van Walsum 2012;Yoo et al 2013; and are trying to identify optimum size for a particular substrate. Recently, Liu et al (2013b) reported variations in sugar production and process toxicity with respect to particle size during steam explosion pretreatment (200°C for 5 min) of corn stover.…”

Understanding physicochemical changes in pretreated and enzyme hydrolysed hemp (Cannabis sativa) biomass for biorefinery development

“…Previous studies conducted on different biomass have reported that lime pretreatment shows relatively high yield of reducing sugars after enzyme hydrolysis in comparison to other pretreatments [19,20]. Researchers have investigated high concentration of acid and alkaline at higher temperature and pressure condition to obtain better pretreatment efficiency of the biomass [21,22].…”

Microwave irradiation – A green and efficient way to pretreat biomass

“…In addition, biomass could release acid compounds such as acetic acid in high-temperature processing which could be employed as the catalyst for autohydrolysis (Garrote et al, 2007). The most commonly used base was NaOH (Chen et al, 2013).…”