Maximum Total Reducing Sugar Yield Research Articles

Synthesis of gold nanoparticles using bacterial cellulase and its role in saccharification and bioethanol production from aquatic weeds

In this investigation, gold nanoparticles (AuNPs) were synthesized using cellulase (partially purified from Glutamicibacter arilaitensis strain ALA4) as reducing agent. The biosynthesis of AuNPs was confirmed by observing the appearance of purple colour solution with surface plasmon resonance absorption peak (λmax) at 574 nm. The SEM analysis showed the synthesis of gold nanocrystals with an average size of 5–7 nm. Cellulase was partially purified from strain ALA4 using standard protocols, and further immobilized on AuNPs for assessing its role in the saccharification of alkali (4% w/v NaOH) pre-treated aquatic weeds (Alternanthera philoxeroides and Brachiaria mutica) biomass. The pre-treated biomass of A. philoxeroides exhibited maximum total reducing sugar (TRS) yield of 18.95 ± 0.18 mg/g at 72 h. The pre-treated biomass exhibited increased saccharification degree of 38.25 ± 0.8, 49.05 ± 0.7, 67.05 ± 0.7, 85.27 ± 0.8, and 67.99 ± 0.8% from 12 to 96 h. Likewise, the pre-treated biomass of B. mutica exhibited maximum TRS yield of 20.98 ± 0.17 mg/g at 72 h. The pre-treated biomass exhibited increased saccharification degree of 44.46 ± 0.7, 55.53 ± 0.8, 73.26 ± 0.7, 94.41 ± 0.8, and 73.3 ± 0.7% from 12 to 96 h. Bioethanol production from pre-treated aquatic weeds were estimated by simultaneous saccharification and fermentation process using yeast cells immobilized on sodium alginate. Ethanol content was estimated using Gas Chromatography. The yeast cells immobilized in calcium alginate beads showed ethanol production of 45.09 and 50.1% from NaOH pre-treated A. philoxeroides and B. mutica biomass, respectively. Findings of this study suggested pronounced role of bacterial cellulase-assisted-synthesized AuNPs in biofuel industries for the successful production of bioethanol from distinct aquatic weeds biomass in a cost-effective manner in future.

Conversion of Babool wood residue to 5-Hydroxymethyl Furfural: Kinetics and Process modelling

This study proposes an integrated approach for the formation of total reducing sugars (TRS) and 5-hydroxymethyl furfural (5-HMF) from forestry biomass. Detailed kinetics was studied using an irreversible series model and the developed kinetic model is congruent with the experimental data. The obtained rate constants were also applied to gain insight for designing continuous reactor configurations. Maximum TRS (32.28%) and 5-HMF yield (42.32%) was obtained in 67.13 min and 311.62 min at 120 °C using single-stage CSTR whereas complete conversion of TRS was observed in 17.03 min with significant 5-HMF yield (23.68%) in 39.07 min at 120 °C using two equal-sized CSTR in series. Also, maximum TRS yield (30.61%) and 5-HMF yield (58.41%) was observed in 67.13 min and 193.38 min respectively using single-stage PFR. The proposed model for Babool wood hydrolysis will be valuable to facilitate the cost-effective and sustainable conversion of waste biomass to bio-based fuels.

Novel strategies for glucose production from biomass using heteropoly acid catalyst

Abstract Bioethanol and direct glucose fuel cells pledged clean energy to the world. Cellulose depolymerization for glucose production has been a successful approach in bioethanol production. Heteropoly acids (HPAs) are strong Bronsted solid acid catalysts for biomass hydrolysis. Keggin type HPAs, namely, Silicotungstic acid (HSiW), Phosphotungstic acid (HPW), and Phosphomolybdic acid (HPMo), were used for the hydrolysis of lignocellulosic biomass to glucose. Five different biomass feedstocks, namely, miscanthus, sugarcane leaves, switchgrass, sunflower seeds, and bamboo leaves, were examined for the feasibility of total reducing sugar (TRS) yield through the composition analysis and catalytic biomass hydrolysis. Sunflower seeds contained the maximum holocellulose with 90.6%, and switchgrass contained the least i.e., 77.63%. Among the five biomass tested, switchgrass resulted in the highest TRS (5.77 wt/dry wt. %) with HPMo catalyst at a catalyst to biomass ratio of 30:100 (wt./wt. %), a reaction temperature of 120 °C for 3 h. The reaction parameters for depolymerization were optimized for all three HPAs, and the optimized conditions were 3 h and 120 °C. HPMo showed maximum TRS yield (5.77 wt/dry wt.%) among the three HPAs at 30:100 catalyst to biomass ratio. However, a catalyst to biomass ratio of 20:100 (wt./wt.%) was economical (5.25 wt/dry wt.%) for commercial application.

Assessment of combination of pretreatment of Sorghum durra stalk and production of chimeric enzyme (β-glucosidase and endo β-1,4 glucanase, CtGH1-L1-CtGH5-F194A) and cellobiohydrolase (CtCBH5A) for saccharification to produce bioethanol

Optimization of pretreatment and saccharification of Sorghum durra stalk (Sds) was carried out. The chimeric enzyme (CtGH1-L1-CtGH5-F194A) having β-glucosidase (CtGH1) and endo β-1,4 glucanase activity (CtGH5-F194A) and cellobiohydrolase (CtCBH5A) from Clostridium thermocellum were used for saccharification. Chimeric enzyme will save production cost of two enzymes, individually. Stage 2 pretreatment by 1% (w/v) NaOH assisted autoclaving + 1.5% (v/v) dilute H2SO4 assisted oven heating gave lower total sugar yield (366.6 mg/g of pretreated Sds) and total glucose yield (195 mg/g of pretreated Sds) in pretreated hydrolysate with highest crystallinity index 55.6% than the other stage 2 pretreatments. Optimized parameters for saccharification of above stage 2 pretreated biomass were 3% (w/v) biomass concentration, enzyme (chimera: cellobiohydrolase) ratio, 2:3 (U/g) of biomass, total enzyme loading (350 U/g of pretreated biomass), 24 h and 30 °C. Best stage 2 pretreated Sds under optimized enzyme saccharification conditions gave maximum total reducing sugar yield 417 mg/g and glucose yield 285 mg/g pretreated biomass in hydrolysate. Best stage 2 pretreated Sds showed significantly higher cellulose, 71.3% and lower lignin, 2.0% and hemicellulose, 12.2% (w/w) content suggesting the effectiveness of method. This hydrolysate upon SHF using Saccharomyces cerevisiae under unoptimized conditions produced ethanol yield, 0.12 g/g of glucose. Abbreviation: Ct-Clostridium thermocellum, Sds-Sorghum durra stalk, TRS-Total reducing sugar, HPLC-High performance liquid chromatography, RI-Refractive index, ADL-acid insoluble lignin, GYE-Glucose yeast extract, MGYP-Malt glucose yeast extract peptone, SHF-separate hydrolysis and fermentation, OD-Optical density, PVDF-Poly vinylidene fluoride, TS-total sugar, FESEM-Field emission scanning electron microscopy, XRD-X-ray diffraction, FTIR-Fourier transform infra-red spectroscopy and CrI-Crystallinity index.

Evaluation of pre-treatment methods for Lantana camara stem for enhanced enzymatic saccharification.

This study evaluates certain pre-treatment methods for Lantana camara stem for efficient conversion to fermentable sugars. The composition analysis of L. camara stem showed 66.8% (w/w) holocellulose, 34.9% (w/w) cellulose and 17% (w/w) hemicellulose. Comparative analysis of various chemical, physical or physico-chemical pre-treatments on L. camara stem was performed. Of all pretreatment methods used, pre-treatment with 1% (v/v) H2SO4 assisted autoclaving gave maximum total reducing sugar yield 132.7mg/g (13.2g/L) of raw biomass in pretreated hydrolysate. Major contribution to total reducing sugar was from hemicellulosic fraction, because total pentose sugar yield was 119.4mg/g of raw biomass whereas, glucose released was only 10mg/g of untreated biomass. The enzymatic saccharification of pre-treated L. camara stem by 1% (v/v) H2SO4 assisted autoclaving was performed with partially purified carboxymethylcellulase from Bacillus amyloliquefaciens SS35. Enzymatic saccharification at 30°C for 48h gave total reducing sugar yield, 63.3mg/g of pre-treated biomass in the hydrolysate, while untreated biomass gave 43.3mg/g of untreated biomass. The total sugar yield i.e. the sum of pre-treated biomass hydrolysate total reducing sugar (132.7mg/g of raw biomass) and enzymatic hydrolysate total reducing sugar (63.3mg/g of pre-treated biomass) was 196.0mg/g of raw biomass, indicating the effectiveness of pre-treatment method. Field emission scanning electron microscopy, Fourier transform infrared and X-ray diffraction analyses displayed enhanced porosity, removal of non-cellulosic sugars and increased cellulose crystallinity, respectively, in pre-treated L. camara stem, showing the effectiveness of acid assisted autoclaving pre-treatment.

Efficient hydrolysis of Babool wood (Acacia nilotica) to total reducing sugars using acid/ionic liquid combination catalyzed by modified activated carbon

This study aims to examine the potential of Babool wood (Acacia nilotica) as an alternative and sustainable resource to produce value added chemicals and/or useful intermediates like sugars. The performance of Babool wood digestability and hydrolysis to sugars was compared using three acids: H2SO4/H3PO4/HCl and ionic liquid [Bmim] Cl catalyzed by modified activated carbon. Hydrolysis using sulphuric acid treated Babool wood leads to the formation of total reducing sugar (TRS) ranging from 53.34% to 83.67% yield under different conditions. Babool wood treated with acid was characterized using Fourier Transformation Infrared Spectroscopy, X- Ray Diffraction and Lignocellulosic compositional analysis. Further, the effect of process variables such as acid strength, acid concentration, acid to Babool wood ratio, Babool wood particle size, hydrolysis time, and temperature on the TRS yield was explored. Maximum TRS yield was observed to be 83.67% in a reaction time of 60 min using −80 + 100 mesh of Babool wood at 393 K. Kinetic results were successfully simulated with literature model (R2 > 0.9) for rate of formation of sugar. This study provides a single step approach for Babool wood hydrolysis to sugars.

Hydrolysis of cellulose with one-pot synthesized sulfonated carbonaceous solid acid

Cellulose could be effectively hydrolyzed into reducing sugars with a novel sulfonated carbonaceous solid acid. The catalyst bearing both cellulose catalytic sites (–SO3H) and binding sites (–Cl) was synthesized by one-pot carbonization of sucralose with p-toluenesulfonic acid, bypassing the use of concentrated sulphuric acid and without any post-modification. Influences of reaction time and temperature, water content in ionic liquid, dosage of catalyst and substrate on the yield of total reducing sugars (TRS) from cellulose were investigated. A maximum TRS yield of 67.6% was obtained in the 1-butyl-3-methyl imidazolium chloride at 130°C in 60min, which was much higher than that hydrolyzed by the –Cl free solid acid (36.1%). The excellent catalytic performance of the prepared solid acid can be attributed to the synergic effect of –SO3H and –Cl groups. This work provided a green method to synthesize sulfonated carbonaceous solid acid for efficient conversion of biomass into biofuels.

Two-stage thermophilic bio-hydrogen and methane production from oil palm trunk hydrolysate using Thermoanaerobacterium thermosaccharolyticum KKU19

The two-stage process for thermophilic bio-hydrogen production followed by methane production was examined on a hydrolysate obtained from oil palm trunk (OPT). The optimum conditions for lime pretreatment and enzymatic hydrolysis of OPT was a lime loading of 0.2 g Ca(OH)2/g-OPT, pretreatment time of 60 min, temperature of 121 °C and enzyme loading of 35 filter paper units/g-OPT. A maximum total reducing sugar yield of 473 mg/g-OPT was obtained, which was 2.7-fold higher than that of untreated OPT. The OPT hydrolysate was used as a substrate for bio-hydrogen production by Thermoanaerobacterium thermosaccharolyticum KKU19 in the first stage. The maximum hydrogen production potential of 2179 mL H2/Lsubstrate was obtained under the optimum conditions of 16.5 g/L initial substrate concentration, initial pH of 6.7 and 54.5 °C, respectively. Acidic effluent was used to produce methane in the second stage in which the methane yield of 272.4 mL/g-chemical oxygen demand (COD) was achieved. The two-stage hydrogen and methane production resulted in energy yield of 10.6 kJ/g-CODadded with 83% COD removal.

Effect of Subsequent Dilute Acid and Enzymatic Hydrolysis on Reducing Sugar Production from Sugarcane Bagasse and Spent Citronella Biomass

This work was aimed at investigating the effect of process parameters on dilute acid pretreatment and enzymatic hydrolysis of spent citronella biomass (after citronella oil extraction) and sugarcane bagasse on total reducing sugar (TRS) yield. In acid pretreatment, the parameters studied were acid concentration, temperature, and time. At the optimized condition (0.1 M H2SO4, 120°C, and 120 min), maximum TRS obtained was 452.27 mg·g−1and 487.50 mg·g−1for bagasse and citronella, respectively. Enzymatic hydrolysis of the pretreated biomass usingTrichoderma reesei26291 showed maximum TRS yield of 226.99 mg·g−1for citronella and 282.85 mg·g−1for bagasse at 10 FPU, 50°C, and 48 hr. The maximum crystallinity index (CI) of bagasse and citronella after acid pretreatment obtained from X-ray diffraction analysis was 64.41% and 56.18%, respectively. Decreased CI after enzymatic hydrolysis process to 37.28% and 34.16% for bagasse and citronella, respectively, revealed effective conversion of crystalline cellulose to glucose. SEM analysis of the untreated and treated biomass revealed significant hydrolysis of holocellulose and disruption of lignin.

Pretreatment of microalgal biomass for enhanced recovery/extraction of reducing sugars and proteins

Microalgae species including Chlamydomonas mexicana, Micractinium reisseri, Scenedesmus obliquus and Tribonema aequale were cultivated in batch cultures, and their biochemical composition was determined. C. mexicana showed the highest carbohydrate content of 52.6% and was selected for further study. Sonication pretreatment under optimum conditions (at 40 kHz, 2.2 Kw, 50 °C for 15 min) released 74 ± 2.7 mg g(-1) of total reducing sugars (TRS) of dry cell weight, while the combined sonication and enzymatic hydrolysis treatment enhanced the TRS yield by fourfold (280.5 ± 4.9 mg g(-1)). The optimal ratio of enzyme [E]:substrate [S] for maximum TRS yield was [1]:[5] at 50 °C and pH 5. Combined sonication and hydrolysis treatment released 7.3% (27.1 ± 0.9 mg g(-1)) soluble protein of dry cell weight, and further fermentation of the dissolved carbohydrate fraction enhanced the soluble protein content up to 56% (228.4 mg g(-1)) of total protein content. Scanning and transmission electron microscopic analyses indicated that microalgae cells were significantly disrupted by the combined sonication and enzyme hydrolysis treatment. This study indicates that pretreatment and subsequent fermentation of the microalgal biomass enhance the recovery of carbohydrates and proteins which can be used as feedstocks for generation of biofuels.

Optimization of Alkaline and Dilute Acid Pretreatment of Agave Bagasse by Response Surface Methodology.

Utilization of lignocellulosic materials for the production of value-added chemicals or biofuels generally requires a pretreatment process to overcome the recalcitrance of the plant biomass for further enzymatic hydrolysis and fermentation stages. Two of the most employed pretreatment processes are the ones that used dilute acid (DA) and alkaline (AL) catalyst providing specific effects on the physicochemical structure of the biomass, such as high xylan and lignin removal for DA and AL, respectively. Another important effect that need to be studied is the use of a high solids pretreatment (≥15%) since offers many advantaged over lower solids loadings, including increased sugar and ethanol concentrations (in combination with a high solids saccharification), which will be reflected in lower capital costs; however, this data is currently limited. In this study, several variables, such as catalyst loading, retention time, and solids loading, were studied using response surface methodology (RSM) based on a factorial central composite design of DA and AL pretreatment on agave bagasse using a range of solids from 3 to 30% (w/w) to obtain optimal process conditions for each pretreatment. Subsequently enzymatic hydrolysis was performed using Novozymes Cellic CTec2 and HTec2 presented as total reducing sugar (TRS) yield. Pretreated biomass was characterized by wet-chemistry techniques and selected samples were analyzed by calorimetric techniques, and scanning electron/confocal fluorescent microscopy. RSM was also used to optimize the pretreatment conditions for maximum TRS yield. The optimum conditions were determined for AL pretreatment: 1.87% NaOH concentration, 50.3 min and 13.1% solids loading, whereas DA pretreatment: 2.1% acid concentration, 33.8 min and 8.5% solids loading.

Hydrolysis of bamboo biomass by subcritical water treatment

The aim of present study was to obtain total reducing sugars (TRS) from bamboo under subcritical water (SCW) treatment in a batch reactor at the temperature ranging from 170°C to 220°C and 40min hydrolysis time. Experiments were performed to investigate the effects of temperature and time on TRS yield. The maximum TRS yield (42.21%) was obtained at lower temperature (180°C), however longer reaction time (25min). X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) analysis were used to characterise treated and untreated bamboo samples. The XRD profile revealed that crystallinity of bamboo increased to 71.90% with increase in temperature up to 210°C and decreased thereafter to 70.92%. The first-order reaction kinetic model was used to fit the experimental data to obtain rate constants. From the Arrhenius plot, activation energy and pre-exponential factor at 25min time were found to be 17.97kJmol−1 and 0.154min−1, respectively.

Efficient hydrolyzation of cellulose in ionic liquid by novel sulfonated biomass-based catalysts

A green and effective approach for comprehensive hydrolyzation of cellulose has been described. Several carbon-based solid acids were successfully prepared using various biomass (glucose, microcrystalline cellulose, bamboo, and rice husk) and used to catalyze cellulose hydrolysis. The acid groups (–SO3H and –COOH) were successfully introduced onto the surface of the carbon-based solid acid catalysts as evidenced by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The structure of the prepared catalysts was characterized by scanning electron microscope and X-ray diffraction. The catalysts showed excellent catalytic performance for hydrolysis of cellulose. To improve the reaction efficiency, ball-milling and solubilization in ionic liquids of cellulose were adopted. A maximum total reducing sugar yield of 81.8 % was obtained in ionic liquid 1-butyl-3-methyl imidazolium chloride at 125 °C for 90 min when the water addition was 10 % of ionic liquid. This study provided a promising strategy to synthesize solid acids from lignocelluloses, which were further used to convert biomass into biofuels and platform chemicals.

SO3H-functionalized acidic ionic liquids as catalysts for the hydrolysis of cellulose

The conversion of cellulose into valuable chemicals to deal with the depletion of fossil fuel has got much attention. Completing the hydrolysis of cellulose under mild conditions is the key step. In this study, six kinds of SO3H-functionalized acidic ionic liquids were used as acid catalyst to promote the hydrolysis of cellulose in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl). All of them were efficient for the hydrolysis of cellulose, with the maximum total reducing sugars (TRS) yields over 83% at 100°C. Acidic ionic liquids with analogous structures showed similar catalytic activities. Triethyl-(3-sulfo-propyl)-ammonium hydrogen sulfate (IL-5 in this study) was the optimum ionic liquid for cellulose hydrolysis, with the maximum TRS yield at 100°C up to 99% when the dosage used was 0.2g. In addition, the water in [BMIM]Cl had negative effect on cellulose hydrolysis. Therefore, controlling the content of water in a comparatively low level is quite necessary.