Discussion on Sixty years journey of the Indian Parliament

Bioresource technology, 2016

Cotton stalk, a widely available and cheap agricultural residue lacking economic alternatives, was subjected to steam explosion in the range 170-200°C for 5min. Steam explosion at 200°C and 5min led to significant hemicellulose solubilization (71.90±0.10%). Alkaline extraction of steam exploded cotton stalk (SECOH) using 3% NaOH at room temperature for 6h led to 85.07±1.43% lignin removal with complete hemicellulose solubilization. Besides, this combined pretreatment allowed a high recovery of the cellulosic fraction from the biomass. Enzymatic saccharification was studied between steam exploded cotton stalk (SECS) and SECOH using different cellulase loadings. SECOH gave a maximum of 785.30±8.28mg/g reducing sugars with saccharification efficiency of 82.13±0.72%. Subsequently, fermentation of SECOH hydrolysate containing sugars (68.20±1.16g/L) with Saccharomyces cerevisiae produced 23.17±0.84g/L ethanol with 0.44g/g yield.

Biotechnology and Bioengineering, 1983

Pretreatment of bagasse by autohydrolysis at 200OC for 4 min and explosive defibration resulted in the solubilization of 90% of the hemicellulose (a heteroxylan) and in the production of a pulp that was highly susceptible to hydrolysis by cellulases from Trichoderma reesei C-30 and QM 9414, and by a commercial preparation, Meicelase. Saccharification yields of 50% resulted after 24 h at 50°C (pH 5.0) in enzymic digests containing 10% (w/v) bagasse pulps and 20 filter paper cellulase units (FPU). Saccharifications could be increased to more than 80% at 24 h by the addition of exogenous 6-glucosidase from Aspergillus niger. The crystallinity of cellulose in bagasse remained unchanged following autohydrolysis-explosion and did not appear to hinder the rate or extent of hydrolysis of cellulose. Autohydrolysis-exploded pulps extracted with alkali or ethanol to remove lignin resulted in lower conversions of cellulose (28-3670 after 25 h) than unextracted pulps. Alkali extracted pulps arising from autohydrolysis times of more than 10 min at 200°C were less susceptible to enzymic hydrolysis than unextracted pulps and alkali-extracted pulps arising from short autohydrolysis times (e.g., 2 min at 200°C). Autohydrolysis-explosion was as effective a pretreatment method as 0.25M NaOH (7OoC/2 h); both yielded pulps that resulted in high cellulose conversions with T. reesei cellulase preparations and Meicelase. Supplementation of T. reesei C-30 cellulase preparations with A . niger P-glucosidases was effective in promoting the conversion of cellulose into glucose. A ratio of FPU to 0-glucosidase of 1:1.25 was the minimum requirement to achieve more than 80% conversion of cellulose into glucose within 24 h. Other factors which influenced the extent of saccharification of autohydrolysisexploded bagasse pulps were the enzyme-substrate ratio, the substrate concentration, and the saccharification mode.

Bioresource Technology, 2018

The aim of this study was to investigate a pretreatment by combined H 2 SO 4 acid-catalyst and thermomechanical process to improve hemicelluloses solubilization of hemp hurds and subsequently enzymatic hydrolysis extent of potentially fermentable sugars. It was found that the sugars released were gradually increased with treatment severity. Soluble sugars generated before enzymatic hydrolysis (R 1) increased up to 2.23 g/L indicating that autohydrolysis reaction occurred during pretreatment. Consequently, the solubilization of hemicelluloses was correlated with combined severity factor (CS). As a result, increase of overall reducing sugars (ORS) from 23.4% (untreated) to 81.4% was observed at optimized conditions of steaming temperature of 165 °C for 30 min and acid loading of 62.9 g/kg DM (dry material) corresponding to CS=1.2, with limited production of identified by-products: 0.035 g/L and 0.46 g/L (per 100 g DM) for furfural and HMF, respectively. Structural and physicochemical modifications of biomass were observed by FTIR, A BET and SEM.

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...

2010

This work studies the influence of dry solids load, enzymes ratio and reaction time in sugars concentration and yield of enzymatic hydrolysis of different steam exploded grain straw. Enzymatic hydrolysis was performed using a mixture of cellulase, glucosidade and xylanase, enzymes kindly donated by Novozymes, in test flasks shaken in a rotary incubator at 300 rpm, 50 ºC and pH of 4.8. After 24 h of reaction time, the higher sugars concentration in the hydrolizates was obtained when a 10 % DS was tested (24 g/L for rye straw and 28.1 g/L for wheat straw). When a 10 % DS was tested, maximum glucose and xylose relase after 24 h (84.9 and 19.1 % respectively) were obtained for 1.5:0.5:1.5 enzyme ratio for rye straw, whereas for wheat straw, maximum yield for glucose and xylose (78 % and 29.5 % respectively) were obtained for 1.5:1:1.5, after 24 h of hydrolysis.

Journal of Chemical …, 2006

Sugarcane bagasse was pretreated by wet oxidation (WO) at 195 C for 15 min under either alkaline, neutral or acidic conditions, and by steam explosion (STEX) at 205 C for 10 min. Alkaline WO was more favourable than neutral and acidic WO for the following enzymatic ...

Brazilian Journal of Chemical Engineering, 2014

To change the recalcitrant nature of the lignocellulosic material for maximum hydrolysis yield, a comprehensive study was done by using sulphuric acid as an exclusive catalyst for the pretreatment process. The enzymatic digestibility of the biomass [Water Hyacinth: Eichhornia crassipes] after pretreatment was determined by measuring the hydrolysis yield of the pretreated material obtained from twenty four different pretreatment conditions. These included different concentrations of sulphuric acid (0.0, 1.0, 2.0 and 3.0%), at two different temperatures (108 and 121 °C) for different residence times (1.0, 2.0 and 3.0h).The highest reducing sugar yield (36.65 g/L) from enzymatic hydrolysis was obtained when plant material was pretreated at 121 °C for 1.0 h residence time using 3.0% (v/v) sulphuric acid and at 1:10 (w/v) solid to liquid ratio. The total reducing sugars obtained from the two-stage process (pretreatment + enzymatic hydrolysis) was 69.6g/L. The resulting sugars were fermented into ethanol by using Saccharomyces cerevisiae. The ethanol yield from the enzymatic hydrolyzate was 95.2% of the theoretical yield (0.51g/g glucose), as determined by GS-MS, and nearly 100% since no reducing sugars were detected in the fermenting media by TLC and DNS analysis.

2010

Steam pretreatment is one of the most efficient pretreatment technologies employed prior to enzymatic hydrolysis of lignocellulosics to obtain high polysaccharide conversion. In this study, steam pretreatment of non-impregnated hemp hurds was investigated at two reactor scales (2 and 10 L) by varying the temperature from 200-230°C. Glucan recoveries were relatively high (> 82 % of original content), while xylan recoveries ranged from 18-66 % of original. Conversions of glucan and xylan in enzymatic hydrolysis varied between X = 62-83 % and 46-96 %, respectively, based on glucan and xylan contents of the substrate. Ethanol yields in simultaneous saccharification and fermentation ranged from Y = 38-70 %, based on glucan and mannan contents of the substrate. The highest overall glucose yield was 336 g kg-1 dry hurds obtained at 210°C, whereas the maximum sugar yield (glucose + xylose), 414 g kg-1 dry hurds, was achieved at 200°C. The highest ethanol yield, 141 g kg-1 dry hurds, was obtained at 210°C.

Renewable Energy, 2009

The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately. This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.