Dilute mixed-acid pretreatment of sugarcane bagasse for ethanol production (original) (raw)
Related papers
Physical and Chemical Pretreatment of Sugarcane Bagasse for Enhanced Acid Hydrolysis
Cellulose Chemistry and Technology, 2020
The second-generation ethanol production process proceeds in several stages. One of them is the pretreatment of lignocellulosic materials, which consists in the disruption of vegetal fibers, promoting partial removal of lignin and hemicelluloses. Pretreatment methods are of great importance to the effectiveness of the hydrolysis stage due to the increase in accessibility of hydrolysis reagents to the interior of the fibers, improving the conversion of lignocellulosic materials. In this study, a pretreatment of sugarcane bagasse was performed, involving milling and ultrasound treatment in alkaline or acidic medium. After the pretreatments, the materials were submitted to acid hydrolysis reactions. To evaluate the efficiency of the pretreatments, the amount of total reducing sugars (% TRS) of the hydrolysis products were assessed. The best results were obtained for the alkaline pretreatment of sugarcane bagasse, with almost 20% of TRS.
tLignocellulosic ethanol is a promising alternative to gasoline that can be produced by fermentation ofsugars present in lignocellulosic biomass. Improved properties of energy crops and reduction of ligno-cellulose recalcitrance to biological conversion have the potential to reduce production costs. This study evaluated bagasse from 115 varieties of sugarcane for fermentable sugar yield. The purpose was to selectthe preferred varieties with fiber of high processability without compromising juice ethanol and cane yield. Dilute acid pretreatment was employed to improve the sugars yield from the bagasse. The results showed wide variations in structural carbohydrates (as monosaccharide) content (66.6–77.6% dry matter (DM)) and lignin content (14.4–23.1% DM) between varieties. Combined sugar yield obtained after pretreatment and enzymatic hydrolysis also varied significantly (27.3–55.2 g/100 g DM). Further, it was demonstrated that some of the varieties had combined characteristics of high cane productivity and combined sugar yield after pretreatment-hydrolysis of the bagasse. These results suggest the incorporation of selection of varieties, given its contribution for developing a cost-efficient pretreatment and saccharification process.
Glucose production from sugarcane bagasse was investigated. Sugarcane bagasse was pretreated by four different methods: combined acid and alkaline, combined hydrothermal and alkaline, alkaline, and peroxide pretreatment. The raw material and the solid fraction of the pretreated bagasse were characterized according to the composition, SEM, X-ray and FTIR analysis. Glucose production after enzymatic hydrolysis of the pretreated bagasse was also evaluated. All these results were used to develop relationships between these parameters to understand better and improve this process. The results showed that the alkaline pretreatment, using sodium hydroxide, was able to reduce the amount of lignin in the sugarcane bagasse, leading to a better performance in glucose production after the pretreatment process and enzymatic hydrolysis. A good xylose production was also observed.
Thermal and Morphological Evaluation of Chemically Pretreated Sugarcane Bagasse
—Enzymatic hydrolysis is one of the major steps involved in the conversion from sugarcane bagasse to yield ethanol. This process offers potential for yields and selectivity higher, lower energy costs and milder operating conditions than chemical processes. However, the presence of some factors such as lignin content, crystallinity degree of the cellulose, and particle sizes, limits the digestibility of the cellulose present in the lignocellulosic biomasses. Pretreatment aims to improve the access of the enzyme to the substrate. In this study sugarcane bagasse was submitted chemical pretreatment that consisted of two consecutive steps, the first with dilute sulfuric acid (1 % (v/v) H 2 SO 4), and the second with alkaline solutions with different concentrations of NaOH (1, 2, 3 and 4 % (w/v)). Thermal Analysis (TG/ DTG and DTA) was used to evaluate hemicellulose, cellulose and lignin contents in the samples. Scanning Electron Microscopy (SEM) was used to evaluate the morphological structures of the in natura and chemically treated samples. Results showed that pretreatments were effective in chemical degradation of lignocellulosic materials of the samples, and also was possible to observe the morphological changes occurring in the biomasses after pretreatments.
Detritus
Sugarcane bagasse (SB) is made up of cellulose (32-43%), hemicellulose (19-34%) and lignin (14-30%). Due to high recalcitrant nature of SB, pretreatment is required to deconstruct its structure and enrich the cellulosic fraction. A two-stage NaOH and maleic acid pretreatment was applied to SB to enrich its cellulosic fraction. SB used in the present study is composed of cellulose (40.4 wt%), hemicellulose (20.9 wt%), lignin (22.5 wt%) and ash (4.0 wt%). After one-stage NaOH pretreatment, its cellulosic fraction increased to 61.8 wt% and later increased to 80.1 wt% after the second-stage acid pretreatment. Lignin fraction decreased to 3.0 wt% after one-stage NaOH pretreatment and remained unaffected after the acid pretreatment step. Hemicellulose fraction decreased substantially after the second-stage pretreatment with maleic acid. Pretreated SB displayed high crystallinity index and improved enzymatic digestibility. Hydrolysates of pretreated SB contained very low amount of xylose a...
Investigation into the physical–chemical properties of chemically pretreated sugarcane bagasse
Enzymatic hydrolysis is one of the major steps involved in the conversion of sugarcane bagasse into ethanol. Pretreatments break down macrostructures in order to improve the enzyme access to the targeted glycosidic bonds. This study reports on the use of thermoanalytic techniques together with other different techniques for the verification of the structural and morphological changes occurred in sugarcane bagasse subjected to acid and alkaline pretreatments. The techniques evaluated differences in the BET and BJH surface areas, diameter and pore volume investigated by porosimetry, scanning electron microscopy and wettability. Thermal analysis (TG/DTG and DTA) was also used to evaluate the thermal degradation of hemicelluloses, cellulose and lignin contents that remained in the samples after pretreatments. The results show that chemical pretreatments were effective in the degradation of lignocellulosic samples and significant morphological changes occurred after the pretreatments. Acid and alkaline pretreatments caused an increase in the surface area, diameter and volume of pores. Wettability also revealed important effects regarding surface changes of the biomasses. In summary, all tested pretreatments were effective to chemically degrade the macrostructures of sugarcane bagasse that hinder enzymatic hydrolysis in, for instance, the second-generation ethanol production. Graphical Abstract & Glauber Cruz().,-volV) (0123456789().,-volV)
Enzymatic Saccharification of Acid/Alkali Pre-treated, Mill-run, and Depithed Sugarcane Bagasse
Bioresources, 2016
approximately 3 × 10 6 tons of sugarcane bagasse is produced annually by 14 factories located on the north coast of KwaZulu-Natal. It is one of the most readily available lignocellulosic materials for ethanol production through enzymatic saccharification and hydrolysis. Pre-treatment enables disruption of the naturally resistant structure of lignocellulosic biomass to make the cellulose accessible to hydrolysis for conversion to biofuels. In this study, pre-treatment of depithed bagasse and mill-run bagasse was done using acid (3% H2SO4 v/v) followed by alkali (4% NaOH w/v), and the pre-treated solid was subjected to enzymatic hydrolysis. The effects of different conditions for enzymatic saccharification such as enzyme dose, reaction time, and amount of surfactant were studied in detail. The pre-treated substrate (10% w/v) when hydrolysed using 30 FPU/gds/40 FPU/g dry substrate (gds) with 0.4% (v/v) Tween® 80 for 20 h resulted in 608 mg/gds (depithed bagasse) and 604 mg/gds (mill-run bagasse) total reducing sugars.
Sugar Tech
The production potential of cellulosic ethanol from sugarcane bagasse was studied. Chemical pretreatments were carried out by shaking bagasse with 1, 2 and 3% H2O2 (pH 10, 11.5 and 13) for 24, 48 and 72 h with subsequent saccharification of pretreated bagasse with H2SO4 (0.8 and 1.0 M) for 50 min for optimization of process. Acid hydrolysates were fermented with Saccharomyces cerevisiae var ellipsoideus for ethanol production. Maximum weight loss in alkaline pretreatment (52.30%), amount of reducing sugars (520.84 mg/g) and ethanol produced (27.94 ml/100 g pretreated bagasse) were found in 2% H2O2 (pH 11.5, 48 h) pretreated bagasse saccharified with 0.8 M H2SO4 after fermentation for 72 h. Pretreatment followed by acid saccharification decreased the time interval for ethanol fermentation.
Dilute-acid Hydrolysis of Cellulose to Glucose from Sugarcane Bagasse
Chemical Engineering Transactions, 2014
As the main component of lignocelluloses materials, cellulose is a biopolymer consisting of many glucose units connected through ß-1,4-glycosidic bonds. The breakage of the ß-1,4-glycosidic bonds by acids leads to the hydrolysis of cellulose polymers, resulting in the sugar molecule glucose or oligosaccharides. Mineral acids, such as HCl and H2SO4, have been used in the hydrolysis of cellulose. The lignocellulosic materials usually require a first step of pretreatment due to the association between the three major components of plant cell wall (cellulose and hemicelluloses fractions and lignin) in order to make available the monomeric sugars found in these fractions, for fermentation to ethanol. Different procedures have been employed, for example, acid hydrolysis, alkali hydrolysis, steam explosion, among others. The pretreatment using dilute sulfuric acid (acid hydrolysis) is the most widely used for having high efficiency in the separating process of cell wall components resultin...
The structural changes, lignin content and enzymatic hydrolysis of dilute acid pretreated bagasse from 19 varieties of sugarcane were investigated. Chemical compositions varied significantly between the materials. Glucose yield after enzymatic hydrolysis also differed significantly among the samples. The differences in glucose yields were not eliminated by increasing the pretreatment severity. Glucose yield showed a positive correlation with total dye and orange dye adsorption, whereas with blue dye adsorption it showed a weak correlation. The crystallinity index increased with the increasing pretreatment severity as a result of the removal of the amorphous components of the biomass. The degree of polymerization decreased with the increase in pretreatment severity. However, the change in either crystallinity index or degree of polymerization did not correlate with glucose yield. The results suggest that the lignin modification/real-location is a key factor for improving cellulose accessibility of sugarcane bagasse.