Optimization of alkali, big bluestem particle size, and extruder parameters for maxium enzymatic sugar recovery using response surface methodology

Abstract

Extrusion can be a viable continuous biomass pretreatment that industry can adopt readily due to its uniqueness (including pretreatment time less than 90 s) over other pretreatment methods. The current study was undertaken to evaluate the combined effect of alkali soaking and extrusion of big bluestem to improve the sugar recovery to nearly quantitative. In order to evaluate the combined effect of alkali soaking and extrusion on the performance of enzymatic saccharification, big bluestem (2-10 mm) was soaked in different alkali concentrations (0.5-2.5 % w/v NaOH) for 30 min at room temperature and then extruded using a lab scale single screw extruder at various barrel temperatures (45-225°C) and screw speeds (20-200 rpm). Statistical analyses confirmed that all the independent variables considered had a significant effect on sugar recovery. A proposed quadratic model to predict sugar recovery had high F and R2 values with a low p value, and adequately represented the relationship among the independent variables on sugar recovery. The optimum pretreatment condition found was the following: 90°C barrel temperature, 155 rpm screw speed, 2.0% alkali concentration, and 4 mm particle size resulted the maximum glucose, xylose, and combined sugar recovery of 90.1, 91.5, and 89.9%, respectively.

An Experimental and Modeling Study on the Pretreatment and Alkaline Hydrolysis of Blue Agave Bagasse in Twin-Screw Extruders

“…According to the literature, − traces of cellulose and hemicellulose can be hydrolyzed under alkaline conditions, when no other pretreatment sources (e.g., mechanical action of a screw in an extruder) are available. Therefore, the extracted polysaccharides were considered in our model.…”

Modeling of Pretreatment and Combined Alkaline and Enzymatic Hydrolyses of Blue Agave Bagasse in Corotating Twin‐Screw Extruders

“…Alkaline hydrolysis of BAB was carried out as follows: BAB was added to the extruder at the first module; 5, 10, and 15 a) Obtained from Kadam et al; [64] b) Perez-Guerra et al; [94] and c) Pratto et al [58] NaOH/water (w/v %) solutions were fed at the second module of the TSE and neutralized at the sixth zone by using H 3 PO 4 to get a pH of 5.5, at different L S −1 ratios, temperatures, speeds of agitation (rpm), and screw configurations.…”

“…[43] It is reported in the literature that traces of glucose (G) and xylose (X) can be obtained from H and C hydrolyses under alkaline conditions. [92][93][94] We also consider extracted polysaccharides in our model by using the expressions proposed by Sartori et al [73] and Fuertez et al [76] for H, and by Pavars et al [77] and Van Loon et al [78] for C.…”

“…There are several studies focused on the degradation of pure C by microorganisms, such as enzymes and bacteria. [94][95][96][98][99][100][101] In these contributions, amorphous C is degraded much faster, approximately 10 times faster than crystalline C. [55] Thus, we assumed that only amorphous regions are involved in enzymatic hydrolysis, and that the crystalline region is adsorbed onto the substrate. This assumption simplifies cellulase adsorption in the model.…”

“…Higher temperatures were avoided since they could promote enzyme deactivation. [92][93][94][95][96][97][98] Finally, extruded BAB was recovered and analyzed, as reported in section 2.4. The experimental plan shown in Table 9 corresponded to the preliminary exploratory stages of our research program on pretreatment of BAB by bioextrusion or the CES process.…”