Effect of dilute sulfuric acid pretreatment on the physicochemical properties and enzymatic hydrolysis of coffee cut-stems

Abstract

Coffee-cut stems are a potential fermentable sugars source, which can be upgraded in different valueadded products and energy vectors. Nevertheless, there are few reports focused on the acid pretreatment and saccharification processes. Thus, this paper evaluates the effect of the acid pretreatment and saccharification conditions of coffee cut-stems to find the highest sugar yield. Thereafter, the influence of the residence time in the acid pretreatment and the b-glucosidase supplementation in the saccharification process were analyzed. The combined severity factor and crystallinity index were used as metrics to evaluate both processes. In all assays, an increase in the crystallinity index was observed. Furthermore, a nonlinear trend of the combined severity factor respect to the residence time in the acid pretreatment was evidenced. The highest sugar yield was 66.75% with a combined severity factor of 1.84. The better saccharification process was achieved at combined severity factor of 2.01 with a digestibility of 43%. The addition of b-glucosidase in the enzymatic hydrolysis allows increasing the value to 69.07%. Hence, low temperatures, acid concentrations, and the b-glucosidase supplementation allows obtaining a high sugar yield from coffee cut stems.

Preparation of reducing sugars from corncob by solid acid catalytic pretreatment combined with in situ enzymatic hydrolysis

“…Meanwhile, some representative studies in the literature were compared and listed in Table 2. Compared with the enzymatic hydrolysis results of the literature [5,[51][52][53] that were achieved in 72 h (Table 2, entries 1-4), a comparable enzymatic digestibility was obtained by the traditional enzymatic hydrolysis process in this work (Table 2, entry 5). It appears that the hemicellulose and cellulose in the corncob pretreated with MMCSA have achieved almost a complete saccharification by both methods, but the in situ enzymatic hydrolysis method presents obvious advantages over the traditional one.…”

Generation of Reducing Sugars from Corncob by Magnetic Carbon-Based Solid Acid Pretreatment Combined with In Situ Enzymatic Hydrolysis

“…Meanwhile, some representative studies in the literature were compared and listed in Table 2. Compared with the enzymatic hydrolysis results of the literature (Ge et al 2020;Solarte-Toro et al 2020;Wang et al 2019;Yuan et al 2019) that were achieved in 72 h (Table 2, entries 1-4), a comparable enzymatic digestibility was obtained by the traditional enzymatic hydrolysis process in this work (Table 2, entry 5). It appears that the hemicellulose and cellulose in the corncob pretreated with MMCSA has achieved almost a complete sacchari cation by both methods, but the in situ enzymatic hydrolysis method presents obvious advantages over the traditional one.…”

Dilute acid pretreatment for enhancing the enzymatic saccharification of agroresidues using a Botrytis ricini endoglucanase

“…The highest levels of RS were observed in sugarcane bagasse treated with 1.5% acid (911 mg⋅g −1 ), in rice husk with 1% acid (764 mg⋅g −1 ), and wheat bran with 0.5% acid (406.5 mg⋅g −1 ). The use of diluted sulfuric acid caused 89.5% of hemicellulose solubilization and 82% of monomeric sugars production of sugarcane bagasse 22 About 30% of lignin removal was obtained after pretreatment of Napier grass with 3% sulfuric acid 23 The maximum glucose yield (54.5%) was obtained with 0.05% sulfuric acid in acacia wood 24 The highest sugar yield was 66.75% after treatment of coffee‐cut stems with acid pretreatment 25 The lignocellulosic degradation with the use of imidazole was dependent on temperature, and the best result for the recovery of cellulose (62.4% w/w) was obtained at 170°C for 2 h 26 Thus, the lignocellulosic degradation and release of reducing sugar depend on the pretreatments, contents of bases and acid, and biomass.…”