Formation Of Sugars Research Articles

Effect of Surfactant HLB Value on Enzymatic Hydrolysis of Chitosan

Nonionic surfactants are reported as being able to enhance enzyme stability and increase the conversion of enzymatic reactions. Surfactant-assisted enzymatic hydrolysis conversion is affected by surfactant HLB values. This work investigated the influence of nonionic surfactants with different HLB values on chitosan enzymatic hydrolysis using cellulase enzyme by measuring the reducing sugars formation, viscosity, and molecular weight of hydrolyzed chitosan. A characterization analysis of hydrolyzed products was also carried out. A higher HLB value exhibits a better enzymatic chitosan hydrolysis performance, shown by the decrease in a solution’s viscosity and the increase in reducing sugar formation. Increasing the surfactant concentration will also increase the hydrolysis rate. Nonionic surfactants can protect cellulase enzyme from the denaturation of temperature and stirring influence. The higher the HLB value, the lower the molecular weight of the hydrolyzed chitosan. The result of UV–Vis demonstrated aldehyde groups formation during hydrolysis. The SEM analysis showed that the chitosan, hydrolyzed using different HLB values of surfactants, had different surface morphologies. However, it did not change the chemical structure of the hydrolysis product seen by the FTIR analysis. The XRD patterns showed that the relative crystallinity of raw chitosan decreased when hydrolyzed with surfactants.

Effects of pH and Osmotic Changes on the Metabolic Expressions of Bacillus subtilis Strain 168 in Metabolite Pathways including Leucine Metabolism.

Bacillus subtilis is often exposed to diverse culture conditions with the aim of improving hygiene or food quality. This can lead to changes in the volatile metabolite profiles related to the quality of fermented foods. To comprehensively interpret the associated metabolic expressions, changes in intracellular primary and extracellular secondary volatile metabolites were investigated by exposing B. subtilis to an alkaline pH (BP, pH 8.0) and a high salt concentration (BS, 1 M). In particular, B. subtilis was cultured in a leucine-enriched medium to investigate the formation of leucine-derived volatile metabolites. This study observed metabolic changes in several metabolic pathways, including carbohydrate metabolism, amino acid metabolism, fatty acid metabolism, and leucine degradation. The formation of proline (an osmolyte), furans, pyrrole, and monosaccharide sugars (glucose, galactose, and fructose) was enhanced in BS, whereas fatty acid derivatives (ketones and alcohols) increased in BP. In the case of leucine degradation, 3-methyl-butanal and 3-methylbutanol could be salt-specific metabolites, while the contents of 3-methylbutanoic acid and 3-methylbutylacetate increased in BP. These results show culture condition-specific metabolic changes, especially secondary volatile metabolites related to the sensory property of foods, in B. subtilis.

Important role of seawater radiolysis of the World Ocean in the chemical evolution of the early Earth

It is generally recognized that the evolution of early Earth was affected by an external energy source: radiation from the early Sun. We also propose and substantiate the hypothesis of important role of natural radioactivity, as an internal energy source, in the evolution of early Earth. Radioactive isotopes have been present on Earth since its formation. The decay of long-lived 232Th, 238U, 238U, and 40K was an important source of energy and, together with accretion of interplanetary matter and the action of gravitational forces, it promoted melting and differentiation of matter and tectonic activity of early Earth. At the same time, radioactive isotopes initiated radiation-chemical transformations of the Earth's matter and contributed to the chemical evolution of the planet. The initial content of radioactive isotopes in the World Ocean of the early Earth and the kinetics of their decay, the values of the absorbed dose and dose rate, as well as the efficiency of seawater radiolysis as a function of time are calculated. It is shown that the decay of long-lived isotopes initiated radiation chemical reactions of compounds dissolved in the ocean and gave rise to oxygen. The ocean served as a “reservoir” that collected components of the early atmosphere and products of their transformations and simultaneously as a “converter” in which further chemical reactions of these compounds took place. The chemical transformations of dissolved inorganic compounds boosted interrelated processes important for evolution: formation of organic matter, including prebiotic molecules, purification of the ocean, and oxygenation of hydro- and atmosphere of Earth. As a result, ocean became the “cradle” for the emergence of life. Radical mechanisms for the formation of simple amino acids, sugars, and nitrogen bases, i.e., the key structures of all living matter, were proposed. The amounts of organic matter and oxygen accumulated with time were calculated; the results confirmed the role of natural radioactivity in the evolution of Earth's matter and the emergence of life. We expect that this hypothesis would become the starting point for considering the important role of natural radioactivity and radiation-chemical processes in the general picture of Earth's evolution and emergence of life.

Novel insight into the effect of fermentation time on quality of Yunnan Congou black tea

Fermentation is a crucial process in black tea processing; however, the effect of fermentation time on the quality of Yunnan Congou black tea has never been assessed. This study aimed to evaluate the quality of Yunnan Congou black tea by detecting quality components, artificial sensory evaluation, and objective attributes under different fermentation times (2, 3, 4, and 5 h). Partial least squares discriminant, odor active value, and least-significant difference analyses were used to identify key differences in its compounds. Overall, 36 non-volatile and 142 volatile compounds were detected. We found that 3 h was the optimal fermentation time for retaining several simple catechins, allowing formation of theaflavins (TFs) and thearubigins (TRs) and promoting formation and conversion of sugars and degradation of flavonoid glycosides. The volatile compounds were most abundant, and sweet and umami comprehensive sensor responses were stronger in the 3 h-fermented samples with the best sensory quality. Nine non-volatile (including TFs, TRs, theabrownins, caffeine, and glucose) and eight volatile (including linalool, phenylacetaldehyde, methyl salicylate, benzaldehyde, 2-pentyl-furan, and trans-β-ionone) markers were identified using multivariate statistical analysis. This study provides technical guidance for directed and standardized production and lays a theoretical foundation for the in-depth study of Yunnan Congou black tea.

Metabolomics mechanism of traditional soy sauce associated with fermentation time

Given that fermentation time has significant impact on quality and flavor of soy sauce, a global understanding of the metabolic mechanism as fermentation time prolonged is essential for producing satisfactory and consistent quality of traditional soy sauce. Herein, the metabolic compounds changes of soy sauce associated with fermentation time up to 10 years were comprehensively investigated by using Chinese traditional fermented soy sauce (CTFSS) as a demonstration. Results showed that formaldehyde nitrogen, total soluble nitrogen (TSN), non-salt soluble solids, amino acids, free 5’-nucleotides and volatile compounds in CTFSS changed obviously during fermentation. Specifically, glutamic acid and aspartic acid were prominent in CTFSS. Continuous decrease in content of hypoxanthine (Hx) was found from 1M (1-month soy sauce) to 7M (7-months soy sauce). Furthermore, a significant opposite tendency for changes between some volatile compounds and amino acids was indicated that there was a transformation between these two components. Therefore, a better understanding to the influence of fermentation time on soy sauce had been proposed. As the formation and conversion of amino acids and sugars might be mainly responsible for flavor formation in CTFSS, the ratio of these two reactions rate led the metabolism to be divided into three steps, degradation, conversion and balance.

Slowing down of starch hydrolysis of glutinous rice and non-glutinous rice flours by black soybean extracts: Cooperation between cyanidin 3-O-glucoside and procyanidins

• Black soybean components inhibited starch hydrolysis by binding to rice flours. • The inhibition was greater in non-glutinous rice flour than glutinous rice flour. • In the components, cyanidin 3- O -glucoside and procyanidins were included. • The inhibition by cyanidin 3- O -glucoside and procyanidins were cooperative. • The cooperation took place in the digestion of amylopectin as well as amylose. Black soybean (BSB), which contains cyanidin 3- O -glucoside (C3G) and procyanidins, is an ordinary ingredient in Japan. The BSB extracts slowed down pancreatin-induced reducing sugar formation and starch hydrolysis more significantly in non-glutinous rice flour (joshin-ko) than glutinous rice flour (mochi-ko), suggesting that BSB components inhibited amylose digestion more effectively than amylopectin digestion. In the components, C3G, a procyanidin dimer (proB2), and procyanidin oligomers were included. C3G could cooperate with proB2 for the inhibition. Procyanidin oligomers inhibited the amylose hydrolysis significantly but slightly the reducing sugar formation in joshin-ko, and inhibited the both reactions slightly in mochi-ko, suggesting that the oligomers could effectively inhibit amylose digestion. C3G could also cooperate with the procyanidin oligomers to inhibit amylose digestion in joshin-ko. The above results suggest that the cooperation of C3G and procyanidins might also be included in the BSB extract-dependent inhibition of amylose digestion in joshin-ko.

Structural Modelling and in-silico characterization of a Novel Thermophilic β-amylase from Clostridium thermosulfuregenes

β-amylase is a hydrolytic enzyme that is involved in breaking down starch and producing energy. Since the discovery of β-amylase, it has been applied in various applications especially in the food industry. In this study, a novel β-amylase from Clostridium thermosuluregen, a thermophilic anaerobic bacterium that ferments its extracellular emulsion to ethanol at 62 ℃ was modelled and studied using bioinformatics tools and compared with B. cereus β-amylases that functions at mesophilic conditions. The results showed that the overall structural conformations, secondary structures, and important residues involved in active and binding sites were identified in both proteins. The results revealed that the modelled β-amylase of C. thermosulfuregen is very similar with respect to the global conformation, location of active and binding sites. Both proteins showed identical structural domains with the thermophilic variant possessing a high percentage of hydrophobic amino acid residues, polar amino acid residues, and differences in secondary composition such as loops and beta sheets as the potential evolutionary thermal adaptations that make it stable enzyme that functions up to 70 ℃. The results suggest that the thermal stability are not dependent on one single unique mechanism and may use one or a combination of the mechanisms to sustain its structural conformation at a higher operating temperature. Overall, considering the common properties of this modelled protein with the β-amylase of B. cereus, it can be assumed that if the β-amylase of C. thermosulfuregen were expressed in-vitro, it would produce a stable protein that possesses the hydrolysis function for C. thermosulfuregen to break down the starch and sugar formation.

Identification of Glycolaldehyde Enol (HOHC═CHOH) in Interstellar Analogue Ices.

Glycolaldehyde is considered the entry point in the aqueous prebiotic formose (Butlerow) reaction although it mainly exists in its unreactive hydrated form in aqueous solution. The characterization of the more reactive nucleophilic enol form under interstellar conditions has remained elusive to date. Here we report on the identification of glycolaldehyde enol (1,2-ethenediol, HOHC═CHOH) in low temperature methanol-bearing ices at temperatures as low as 5 K. Exploiting isotope labeling and isomer-selective photoionization coupled with reflectron time-of-flight mass spectrometry, our results unravel distinct reaction pathways to 1,2-ethenediol, thus demonstrating the kinetic stability, availability for prebiotic sugar formation, and potential detectability in deep space.

Optimization of the catalytic process and increase of the Irpex lacteus cellulases yield for saccharification

Cellulases are key enzymes in the biomass saccharification process. Basidiomycetes are capable of producing the entire complex of cellulases necessary for complete hydrolysis of the substrate. In research used a culture of wood-decay fungus I. lacteus Il-11 capable of active cellulose hydrolysis. The results showed that the citrate buffer system allowed stabilization of cellulases action. With increasing enzyme concentration, the amount of product increases but the rate of sugar formation decreases by 1.3–1.5 times with time (96–120 h). The value of the Michaelis-Menten constant is 0.063 M and the maximum reaction rate is 1.90 μM/min. The optimum concentration of cellulose for saccharification by I. lacteus enzyme complex is in the range of 4–7%. Glycine buffer promotes desorption of the I. lacteus cellulase complex from the substrate. Process flowsheet for the production and increase yield of I. lacteus cellulases is proposed.

Comparative transcriptome analysis reveals key genes potentially related to organic acid and sugar accumulation in loquat.

Organic acids and sugars are the primary components that determine the quality and flavor of loquat fruits. In the present study, major organic acids, sugar content, enzyme activities, and the expression of related genes were analyzed during fruit development in two loquat cultivars, 'JieFangZhong' (JFZ) and 'BaiLi' (BL). Our results showed that the sugar content increased during fruit development in the two cultivars; however, the organic acid content dramatically decreased in the later stages of fruit development. The differences in organic acid and sugar content between the two cultivars primarily occured in the late stage of fruit development and the related enzymes showed dynamic changes in activies during development. Phosphoenolpyruvate carboxylase (PEPC) and mNAD malic dehydrogenase (mNAD-MDH) showed higher activities in JFZ at 95 days after flowering (DAF) than in BL. However, NADP-dependent malic enzyme (NADP-ME) activity was the lowest at 95 DAF in both JFZ and BL with BL showing higher activity compared with JFZ. At 125 DAF, the activity of fructokinase (FRK) was significantly higher in JFZ than in BL. The activity of sucrose synthase (SUSY) in the sucrose cleavage direction (SS-C) was low at early stages of fruit development and increased at 125 DAF. SS-C activity was higher in JFZ than in BL. vAI and sucrose phosphate synthase (SPS) activities were similar in the two both cultivars and increased with fruit development. RNA-sequencing was performed to determine the candidate genes for organic acid and sugar metabolism. Our results showed that the differentially expressed genes (DEGs) with the greated fold changes in the later stages of fruit development between the two cultivars were phosphoenolpyruvate carboxylase 2 (PEPC2), mNAD-malate dehydrogenase (mNAD-MDH), cytosolic NADP-ME (cyNADP-ME2), aluminum-activated malate transporter (ALMT9), subunit A of vacuolar H+-ATPase (VHA-A), vacuolar H+-PPase (VHP1), NAD-sorbitol dehydrogenase (NAD-SDH), fructokinase (FK), sucrose synthase in sucrose cleavage (SS-C), sucrose-phosphate synthase 1 (SPS1), neutral invertase (NI), and vacuolar acid invertase (vAI). The expression of 12 key DEGs was validated by quantitative reverese transcription PCR (RT-qPCR). Our findings will help understand the molecular mechanism of organic acid and sugar formation in loquat, which will aid in breeding high-quality loquat cultivars.

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.

Sensorial and Volatile Analysis of Wines Made from Partially Dehydrated Grapes: An Ontario Case Study

Winemaking in cool climate viticultural areas can pose challenges due to difficulties in achieving optimal ripeness from climatic conditions that tend to vary vintage-to-vintage. To stabilize quality, the use of partially dehydrated grapes has been indicated as beneficial to the production of high-quality wine (“appassimento” style) despite climatic variation. Postharvest wine grape dehydration is a complex process that involves the concentration or formation of sugars, aromas, and flavours. One of the quality challenges facing appassimento style winemaking is elevated levels of undesirable oxidation compounds. The aim of this study was to characterize wines made from a local yeast isolate, Saccharomyces uvarum CN1, which demonstrates limited osmotolerance and may have application to this wine style, as it is a known lower producer of such compounds. Wines made with CN1 were compared to wines made with the accepted commercial standard, S. cerevisiae, EC1118. Fermentations (n = 24) were established at three target starting sugar concentrations from dehydrated Cabernet franc grapes (24.5, 26.0, and 27.5°Brix) and a control (21.5°Brix) and were assessed for volatile organic compound (VOC) composition via gas chromatography-mass spectrometry (GC-MS). Wines also underwent quantitative descriptive analysis to identify and quantify sensory attributes by a trained panel (n = 11). Results show that the wines fermented with the yeast isolate contain significant differences in the concentrations of VOCs in the wines. Sensorially, the wines differed in intensity for a number of attributes, including red fruit aroma, black fruit flavour, and length of finish both within Brix treatments and amongst yeast strains. The most important differentiating factor amongst these wines was the combination of yeast strain at the highest starting sugar concentration (27.5°Brix). These findings may assist winemakers by informing the yeast strain choice for optimizing appassimento style wine quality in cool climates.

АНТИСТРЕССОВОЕ ВОЗДЕЙСТВИЕ ОРГАНОМИНЕРАЛЬНЫХ УДОБРЕНИЙ В АГРОТЕХНОЛОГИИ ОЗИМОЙ ПШЕНИЦЫ

To study the effect of urea mineral fertilizer and new organo-mineral fertilizers Stimulife and potassium gutamate containing humid acids (humates) and selenium bioelement, which can affect the plant’s protective system, enhancing adaptive potential, winter wheat crops were treated with prima herbicide at a dose of 500 ml/ha. Visually, the suppression of crops and stress changes in plants were determined. After that, foliar fertilization with urea and organomineral fertilizers was carried out. The activity of the catalase enzyme (NF 1.11.1.6) of leaves when treated with organo-mineral fertilizers increased by 20.4% on the first day, then the increase decreased and on the fifth day it decreased to 11.2%. This type of change in catalase activity is caused by the protective and stimulating effect of the drugs Stimulife and potassium humate, and the protection of cells from the destructive effect of oxygen under stress. The aboveground mass of plants and area of leaves per plant increased, both with the use of urea up to 5.5% - as a result of additional nutrition, and with organo-mineral fertilizers up to 2.9% – as a protective effect against stressors, as a result of increased physiological and biochemical reactions. The content of sugars and fiber increased from the tillering phase to the tube exit phase, and by earing it decreased to the initial state. Urea treatment reduced the sugar content by up to 40%, as a result of the outflow of low-molecular metabolites from sugar formation processes to protein biosynthesis. The nitrogen content when using urea increased by 11.6%, which was provided by additional nitrogen nutrition.

Impact of exogenous \u03b1-amylases on sugar formation in straight dough wheat bread

The use of bacterial or fungal α-amylases is common in wheat bread production to improve several quality-related parameters such as loaf volume, crust color or staling behavior. To study the impact of exogenous α-amylases on straight dough wheat bread, we quantitated mono-, di- and oligosaccharides and residual α-amylase activity in bread crumb during storage for up to 96 h. Discovery-driven proteomics of the five α-amylase preparations studied showed that only a few different amylases per preparation were responsible for the hydrolytic effect. Compared to the control, the supplementation with α-amylase from Bacillus amyloliquefaciens in wheat dough preparation led to major changes in the sugar composition of bread crumb during storage with the formation of oligosaccharides like maltopentaose, maltohexaose, maltoheptaose, and maltooctaose. A residual activity corresponding to 4.0% of the applied activity was determined in the breads prepared with α-amylase from B. amyloliquefaciens, but no residual activity was detected for any of the other fungal or bacterial α-amylases from Aspergillus oryzae or Thermoactinomyces vulgaris. Whether the detected residual activity is related to the characteristics of bread staling or bread crumb properties must be clarified in further studies.

Autocatalysis in Formose Reaction and Formation of RNA Nucleosides.

Understanding of the abiotic formation of nucleosides under geochemical conditions is currently a major scientific challenge. In this study, free radical pathways for formation of RNA nucleosides with canonical nucleobases are proposed for the first time. The pathways proceed with relatively low energy barriers for the formation of ribose as well as all RNA nucleosides. The formose reaction proceeds either with or without Ca2+ and CaOH+ cations. An autocalytic cycle for the formation of both glycolaldehyde and glyceraldehyde is identified when Ca2+ or CaOH+ cations are involved in the reaction. The results suggest that Ca2+ cations are not involved in the formation of ribose from glyceraldehyde. In addition, these pathways lead to the formation of dihydroxyacetone and d-erythrose. Calculated results show that the glycosidic bond can be formed abiotically between the d-ribose and the nucleobase, where d-ribose forms a cyclic free radical that subsequently reacts with the neutral nucleobase. Involvement of proper nucleobase tautomer is important for the formation of RNA nucleosides. Our approaches provide a solution for the long-standing question of how the glycosidic bond is formed under the abiotic conditions with low energy barriers. The pathways for formation of the sugars without a catalyst are relevant to the formation of sugars in interstellar clouds. On the other hand, the autocalysis in the formose reaction followed by the formation of the nucleosides is appropriate for the abiotic synthesis taking place in the presence of water in the early Earth environment. The Ca2+ and CaOH+ cations appear to be the first nonenzymatic catalytic systems for formation of biomolecules.

Profiling of Low-Molecular-Weight Carbonyls and Protein Modifications in Flavored Milk.

Thermal treatments of dairy products favor oxidations, Maillard reactions, and the formation of sugar or lipid oxidation products. Additives including flavorings might enhance these reactions or even induce further reactions. Here we aimed to characterize protein modifications in four flavored milk drinks using samples along the production chain—raw milk, pasteurization, mixing with flavorings, heat treatment, and the commercial product. Therefore, milk samples were analyzed using a bottom up proteomics approach and a combination of data-independent (MSE) and data-dependent acquisition methods (DDA). Twenty-one small carbonylated lipids were identified by shotgun lipidomics triggering 13 protein modifications. Additionally, two Amadori products, 12 advanced glycation end products (AGEs), and 12 oxidation-related modifications were targeted at the protein level. The most common modifications were lactosylation, formylation, and carboxymethylation. The numbers and distribution of modification sites present in raw milk remained stable after pasteurization and mixing with flavorings, while the final heat treatment significantly increased lactosylation and hexosylation in qualitative and quantitative terms. The processing steps did not significantly affect the numbers of AGE-modified, oxidized/carbonylated, and lipid-carbonylated sites in proteins.

Probing rapid carbon fixation in fast-growing seaweed Ulva meridionalis using stable isotope 13C-labelling

The high growth rate of Ulva seaweeds makes it a potential algal biomass resource. In particular, Ulva meridionalis grows up to fourfold a day. Here, we demonstrated strong carbon fixation by U. meridionalis using 13C stable isotope labelling and traced the 13C flux through sugar metabolites with isotope-ratio mass spectrometry (IR-MS), Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), 13C-nuclear magnetic resonance spectrometry (13C-NMR), and gas chromatography-mass spectrometry (GC–MS). U. meridionalis was first cultured in 13C-labelled enriched artificial seawater for 0–12 h, and the algae were collected every 4 h. U. meridionalis grew 1.8-fold (dry weight), and the 13C ratio reached 40% in 12 h, whereas 13C incorporation hardly occurred under darkness. At the beginning of the light period, 13C was incorporated into nucleic diphosphate (NDP) sugars in 4 h, and 13C labelled peaks were identified using FT-ICR-MS spectra. Using semiquantitative 13C-NMR measurements and GC–MS, 13C was detected in starch and matrix polysaccharides after the formation of NDP sugars. Moreover, the 14:10 light:dark regime resulted into 85% of 13C labelling was achieved after 72 h of cultivation. The rapid 13C uptake by U. meridionalis shows its strong carbon fixation capacity as a promising seaweed biomass feedstock.

Effects of operational conditions on auto-catalyzed and sulfuric-acid-catalyzed hydrothermal pretreatment of sugarcane bagasse at different severity factor

Bagasse, a major by-product of sugarcane-processing industries, has potential to play a significant role as feedstock for production of cellulosic ethanol, platform chemicals, and bio-based commodities. Pretreatment is essential for efficient processing of lignocellulosic feedstocks by biochemical conversion. In this work, auto-catalyzed (A-HTP) and dilute sulfuric-acid-catalyzed (SA-HTP) hydrothermal pretreatment of sugarcane bagasse was investigated, setting the temperature (175−205 °C) and the time (4−51 min) in such a way that the severity factor (SF) was always maintained at one of three predetermined values (2.8, 3.8, and 4.8). The investigation covered the effects of different operational pretreatment conditions on (i) the formation of sugars and water-soluble bioconversion inhibitors, including newly discovered inhibitors such as formaldehyde and p-benzoquinone, in the pretreatment liquid, (ii) the chemical composition and recovery of constituents in the solid phase, as determined using two-step treatment with sulfuric acid, Py-GC/MS, and solid-state NMR, (iii) pseudo-lignin formation, (iv) furan aldehydes in condensates from the gas phase, (v) enzymatic digestibility of pretreated solids, (vi) enzyme inhibition by pretreatment liquids, and (vii) fermentability of pretreatment liquids using Saccharomyces cerevisiae yeast. Glucose and xylose were the predominant sugars in pretreatment liquids from SA-HTP and A-HTP, respectively. For A-HTP, the enzymatic digestibility of the pretreated solids was proportional to the SF, while for SA-HTP no clear trend was observed. The best enzymatic digestibility (above 80%) was achieved for A-HTP performed at SF 4.8. The highest total yields of glucose and xylose, the predominant sugars, were achieved for A-HTP at SF 3.8 and temperatures of 190 °C and 205 °C. The fermentability of the pretreatment liquids by Saccharomyces cerevisiae was lower for SA-HTP than for A-HTP. The investigation suggests that hydrothermal pretreatment of sugarcane bagasse can be performed with good results without addition of sulfuric acid, but that the conditions must be just harsh enough to almost quantitatively solubilize the hemicelluloses.

Evaluation of the effects of different chemical pretreatments in sugarcane bagasse on the response of enzymatic hydrolysis in batch systems subject to high mass loads

In the present study, sugarcane bagasse (SB) was subjected to different pretreatments. The pretreated SB was characterized chemically and structurally and was enzymatically hydrolyzed using a commercial enzyme preparation. Pretreatment with sulfite-NaOH was the most efficient for removing lignin while keeping cellulose intact. In addition, sulfite-NaOH pretreatment presented the best response to the enzymatic hydrolysis of cellulose and xylan, reaching conversions of 90%. The increase in consistency (≥10%) in the enzymatic hydrolysis of SB pretreated with sulfite-NaOH showed a loss of cellulose and xylan conversions efficiencies of 28 and 37%, respectively. However, enzymatic hydrolysis with a consistency of 20% resulted in a maximum rate of glucose and xylose formation of 8.5 and 3.0 g L−1 h−1, respectively, and an enzymatic hydrolysate containing 80 and 33 g L−1 of glucose and xylose, respectively. The enzymatic hydrolysis assay in a bioreactor with 20% consistency promoted faster liquefaction of SB, resulting in a higher maximum rate of glucose production (10.6 g L−1 h−1). The increase in the concentration and rate of formation of fermentable sugars in the enzymatic hydrolysate can partially avoid steps of concentration of the hydrolysate, resulting in less energy consumption and greater productivity of the bioproducts obtained from the hydrolysate, such as cellulosic ethanol (2G ethanol).

Casca da manga como fonte de matéria prima lignocelulósica para obtenção do bioetanol

O uso de combustíveis fósseis tem intensificado cada vez mais a emissão de gases poluentes à atmosfera, dessa forma, o etanol de segunda geração, obtido por matéria prima lignocelulósica surge como alternativa por ser considerado uma energia limpa. O biocombustível pode ser produzido a partir de resíduos gerados da fruticultura, como exemplo, a casca da manga, a qual possui uma composição satisfatória à produção do bioetanol. Este trabalho teve por objetivo, a produção de açúcares fermentescíveis, a partir desta matéria prima, para isso, foi realizado um planejamento fatorial acerca das principais variáveis de interesse no processo, e empregado a técnica da hidrólise ácida. Pôde-se observar, um aumento de 25,49% na formação de açúcares fermentescíveis comparados a composição in natura da matéria em estudo.