Dilute Sulfuric Acid Treatment Research Articles

Comparative Analysis of Pretreatment Methods for Fruit Waste Valorization in Euglena gracilis Cultivation: Impacts on Biomass, β-1,3-Glucan Production, and Photosynthetic Efficiency.

This study explored the sustainable valorization of fruit waste extracts from sugarcane bagasse (SB), banana peel (BP), and watermelon rind (WR) for Euglena gracilis biomass and β-1,3-glucan production. The extracts were prepared using water extraction (WE), high-temperature and pressure treatment (HTP), and dilute sulfuric acid treatment (DSA). The DSA-treated extracts consistently yielded the best results. E. gracilis cultured in SB-DSA showed the highest cell density with a 2.08-fold increase compared to the commercial HUT medium, followed by BP-DSA (1.35-fold) and WR-DSA (1.70-fold). Photosynthetic pigment production increased significantly, with chlorophyll a yield being highest in SB-DSA (1.90-fold increase). The chlorophyll a/b ratio and total carotenoid content also improved, indicating enhanced light-harvesting capacity and photoprotection. Photosynthetic efficiency, measured by chlorophyll fluorescence, notably improved. The maximum quantum yield of PSII (Fv/Fm) increased by up to 25.88% in SB-DSA, suggesting reduced stress and improved overall photosynthetic health. The potential photochemical efficiency (Fv/F0) showed even greater improvements: up to 40.53% in SB-DSA. Cell morphology analysis revealed larger cell aspect ratios, implying a more active cellular physiological state. β-1,3-glucan yield also increased by 23.99%, 12.92%, and 23.38% in SB-DSA, BP-DSA, and WR-DSA, respectively. This study demonstrates the potential of pretreated fruit waste as a cost-effective and sustainable medium for E. gracilis cultivation, offering the dual benefits of waste valorization and high-value compound production. These findings contribute to the development of more efficient biorefinery processes and align with the circular economy principles in food biotechnology.

Efficient enzymatic hydrolysis of active oxygen and solid alkali/dilute sulfuric acid-pretreated corn cob

This work proposed a two-step pretreatment method of cooking with active oxygen and solid alkali (CAOSA) followed by dilute sulfuric acid treatment (DA), to contribute enzymatic hydrolysis of corn cob. The first step, CAOSA pretreatment, removed 83.16 % of the lignin, while the second step, a milder pretreatment with DA further eliminated hemicellulose. After the two-step pretreatment, the cellulose content of the residue reached 66.74 %, and with a solid loading of 5 %, the glucose yield was remarkably high at 98.35 % with a concentration of 36.47 g/L. The optimal conditions of the process were determined as follows: DA with 1 % H2SO4 at a solid-to-liquid ratio of 1:10, a temperature of 110 ℃, and a pretreatment time of 60 min. To confirm the efficacy of the two-step pretreatment, we characterized the samples treated with different methods using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The developed method proposes an effective pretreatment and results in the complete enzymatic hydrolysis of corn cob.

Revalorization of sunflower stalk pith as feedstock for the coproduction of pectin and glucose using a two-step dilute acid pretreatment process

BackgroundSunflower stalk pith, residue from the processing of sunflower, is rich in pectin and cellulose, thereby acting as an economic raw material for the acquisition of these compounds. In order to increase the commercial value of sunflower processing industry, a two-step dilute sulfuric acid treatment process was conducted on spent sunflower stalk pith to obtain the value-added products, pectin and glucose.ResultsIn this study, pectin was firstly extracted under mild acid condition to avoid pectin degradation, which was conducted at 90 °C with a pH of 2.0 for 2 h, and ~0.14 g/g of pectin could be recovered. Then the remaining solids after pectin extraction were subjected to the reinforced treatment process with 0.75% H2SO4 at 150 °C for 30 min to further improve enzymatic hydrolysis efficiency. Moreover, by combining a fed-batch enzymatic hydrolysis strategy, a solid loading content of 16% was successfully achieved and the glucose titer reached 103.1 g/L with a yield of 83.6%.ConclusionFinally, ~140 g pectin and 260 g glucose were produced from 1 kg of raw sunflower stalk pith using the integrated biorefinery process. This work puts forward a two-step dilute acid pretreatment combined with enzymatic hydrolysis method to produce pectin and glucose from sunflower spent waste.

Conversion of Symphytum officinale and Panicum virgatum plant extracts to 5-hydroxymethylfurfural catalysed by metal chlorides in ionic liquids

The present work examined the potential for two plants grown on Canadian soil, Symphytum officinale L. (common comfrey) and Panicum virgatum L. (switchgrass), to produce 5-hydroxymethylfurfural using metal chloride catalysis in two ionic liquids, 1-butyl-3-methylimidazolium chloride or 1-ethyl-3-methylimidazolium chloride. Furthermore, two pre-treatments, namely the dilute sulfuric acid treatment and the methanol extraction, were studied as a way to improve sugar availability and increase 5-hydroxymethylfurfural yields compared with untreated biomass. The 0.5 mol/L H2SO4 hydrolysis under autoclave conditions produced sugar-rich extracts containing 230 ± 23 mg of sugars per gram of hydrolysed biomass for comfrey and 425 ± 13 mg of sugars per gram of hydrolysed biomass for switchgrass. The methanol extraction produced extracts high in simple sugars with concentration of 300 ± 60 mg of sugars per gram of dry extract for comfrey and 202 ± 16 mg of sugars per gram of dry extract for switchgrass. The yield of 5-hydroxymethylfurfural was improved from less than 1% using untreated biomass to 6.04% and 18.0% using dry methanol extracts of comfrey and switchgrass, respectively. These yields, although small, are important, as they show for the first time that a methanol extract could enhance the metal chloride catalysis in ionic liquids for 5-hydroxymethylfurfural production from biomass.

Production of fermentable sugars from corn fiber using soaking in aqueous ammonia (SAA) pretreatment and fermentation to succinic acid using Escherichia coli AFP184

Conversion of corn fiber (CF), a by-product from the corn-to-ethanol conversion process, into fermentable sugar and succinic acid was investigated using soaking in aqueous ammonia (SAA) pretreatment followed by biological conversions, including enzymatic hydrolysis and fermentation using genetically engineered E. coli (AFP184). The SAA pretreatment (using a 15% w/w NH4OH solution at a solid-to-liquid ratio of 1: 10 at 60 °C for 24 h) removed 20-38% of lignin and significantly improved the digestibility of the treated solid (85-99% of glucan digestibility). Following the enzymatic hydrolysis, the sugar-rich hydrolysate was subjected to dilute sulfuric acid treatment (1 wt% sulfuric acid and 120 °C for 1 h), which hydrolyzed the oligosaccharides in the hydrolysate into fermentable monomeric sugars. The mixed sugar hydrolysates containing hexose and pentose obtained from the two-step hydrolysis and SAA pretreatment were fermented to succinic acid using a genetically engineered microorganism, Escherichia coli AFP184, for evaluating the fermentability. Engineered E. coli AFP184 effectively converted soluble sugars in the hydrolysate to succinic acid (20.7 g/L), and the production rate and yield were further enhanced with additional nutrients; the highest concentration of succinic acid was 26.3 g/L for 48 h of fermentation.

Integrated utilization of algal biomass and corn stover for biofuel production

This paper describes a novel route for the utilization of algal and lignocellulosic biomass for biofuel production. Dilute sulfuric acid treatment was employed to destroy the rigid algal cells and generate algal hydrolysate. Algal hydrolysate was used as the reaction medium for the enzymatic hydrolysis of lignocellulose from corn stover. The acid treatment parameters were optimized based on the enzymatic efficiency of corn stover digestion and the promotion mechanism is discussed. The algal residues from the acid treatment process were co-digested with corn stover to generate methane. This study showed that algal hydrolysate can be used as a supplemental feedstock and reaction medium to enhance ethanol production. Furthermore, the residues could be utilized as the nitrogen source during the anaerobic digestion of corn stover.

Treating Distillers’ Grain from the Luzhou Aroma/Flavor Industry To Degrade Fiber

To minimize environmental contamination and waste of resources, distillers’ grain (DG) from the Chinese liquor industry was used to produce reducing sugars for Bacillus thuringiensis cultivation. Four different pretreatments, using sodium hydroxide (0.5–2% w/v, 50–121 °C, 1 h), calcium hydroxide (0.2–4% w/v, 50–121 °C, 1 h), dilute sulfuric acid (0.5–2% w/v, 50–121 °C, 1 h), and hot water (50–121 °C, 1 h), were investigated in order to determine the optimal method for degrading cellulose in DG to produce monomeric sugars. Enzymatic hydrolysis and fermentation followed each pretreatment method. The results showed that the highest yield of monomeric sugars was obtained by using 2% dilute sulfuric acid treatment at 121 °C for 1 h (giving 313 g/kg DG), which was significantly higher (p < 0.001) than the yields obtained using other pretreatment methods. The highest spore count was achieved using this pretreatment with the addition of supplements. The utilization of DG in this study provides a plentiful carbon ...

A sulfuric–lactic acid process for efficient purification of fungal chitosan with intact molecular weight

The most recent method of fungal chitosan purification, i.e., two steps of dilute sulfuric acid treatment, pretreatment of cell wall at room temperature for phosphate removal and extraction of chitosan from the phosphate free cell wall at high temperature, significantly reduces the chitosan molecular weight. This study was aimed at improvement of this method. In the pretreatment step, to choose the best conditions, cell wall of Rhizopus oryzae, containing 9% phosphate, 10% glucosamine, and 21% N-acetyl glucosamine, was treated with sulfuric, lactic, acetic, nitric, or hydrochloric acid, at room temperature. Sulfuric acid showed the best performance in phosphate removal (90%) and cell wall recovery (89%). To avoid depolymerisation of chitosan, hot sulfuric acid extraction was replaced with lactic acid treatment at room temperature, and a pure fungal chitosan was obtained (0.12g/g cell wall). Similar pretreatment and extraction processes were conducted on pure shrimp chitosan and resulted in a chitosan recovery of higher than 87% while the reduction of chitosan viscosity was less than 15%. Therefore, the sulfuric–lactic acid method purified the fungal chitosan without significant molecular weight manipulation.

Preparation of biomass hydrochar derived sulfonated catalysts and their catalytic effects for 5-hydroxymethylfurfural production

Amorphous carbon-based sulfonated catalysts were generated from four kinds of biomass (lignin, cellulose, wood meal and D-xylose) by hydrothermal carbonization at various temperatures (225, 245 and 265 °C) followed by sulfonation, with a yield of 36–56%. All of these catalysts showed aromatic structure, hydroxyl and carboxyl groups, with a density of SO3H groups between 0.56 and 0.87 mmol g−1. 5-Hydroxymethylfurfural (HMF) was produced from inulin in ionic liquids (ILs) in one step with the addition of carbon-based sulfonated catalysts, with a factual yield of 47–65% at 100 °C, 60 min. Moderate extension of reaction time (from 30 to 90 min) and increase of temperature (from 80 to 120 °C) promoted HMF production. Ethyl acetate was used as extractant, and about 39–55% of HMF can be recovered from ILs. One problem with these carbon-based sulfonated catalysts was that they would be partly deactivated in ILs for separate reuse, however, they can be easily regenerated by dilute sulfuric acid treatment. The carbon-based sulfonated catalysts exhibited good catalytic activity compared with traditional solid acid catalysts, and the carbon-based sulfonated catalyst/ILs reaction system showed high reusability. In consideration of the renewable as well as the high catalytic activity abilities, these biomass derived carbon-based sulfonated catalysts would be promising for industrial application.

Bioethanol production using the sequential acid/alkali-pretreated empty palm fruit bunch fiber

Empty palm fruit bunch (EPFB) contains a rigid and ordered fiber structure within a relatively high level of hemicellulose and lignin. To enhance poorly enzymatic digestibility and fermentability, in this a sequential acid/alkali pretreatment strategy was applied to increase the fermentable sugar in EPFB fiber. Cellulose content in the biomass was effectively increased by using dilute sulfuric acid treatment to eliminate hemicellulose followed by highly concentrated sodium hydroxide treatment for delignification. The pretreated biomass consisted of 85.2 ± 1.9% cellulose, 1.8 ± 0.5% hemicellulose, and 9.2 ± 0.3% lignin. Under optimal conditions for enzymatic saccharification, 10% (w/v) of pretreated EPFB fiber was hydrolyzed completely and converted to 70.8 ± 0.8 g/L glucose and 1.8 ± 0.1 g/L xylose with a 83.9% yield efficiency. Simultaneous saccharification and fermentation of the pretreated biomass by Saccharomyces cerevisiae W303-1A produced 37.8 g/L ethanol in 1.5 L fermented medium containing 10% (w/v) pretreated EPFB fiber after 60 h. The ethanol productivity was 0.378 g ethanol/g dry EPFB fiber and 0.45 g ethanol/g glucose after fermentation, with a low concentration of xylose and organic acid metabolites. Also, 88% of fermentable sugar was used by the yeast for ethanol fermentation. These results indicate that sequential acid/alkali pretreatment increased enzymatic digestibility and ethanol productivity.

Molecular-Level Consequences of Biomass Pretreatment by Dilute Sulfuric Acid at Various Temperatures

Ex situ room-temperature 13C nuclear magnetic resonance (NMR) measurements are reported on powdered poplar wood that has been pretreated with dilute sulfuric acid (concentrations up to 1 wt %) for times ranging up to 20 min and at temperatures of 120, 130, 140, and 150 °C. There are significant, albeit not dramatic, changes in the measured NMR spectra of the biomass as result of dilute sulfuric acid treatment. Values of T1 for 13C and 1H, as well as TCH and T1ρH, were measured for lignin peaks and cellulose peaks in the 13C NMR spectra, as potential indicators of the degree of atomic-level motion. For lignin components, one finds a trend to larger TCH values as the treatment time or H2SO4 concentration is increased for treatment temperatures of 120 and 130 °C; however, for treatment temperatures of 140 and 150 °C, TCH apparently decreases as the treatment time is increased. This higher temperature TCH behavior implies that the lignin may actually become more rigid at later stages of treatment at temperatu...

Comparison of Feedstock Pretreatment Performance and Its Effect on Soluble Sugar Availability

Cellulosic feedstocks for bioenergy differ in composition and processing requirements for efficient conversion to chemicals and fuels. This study discusses and compares the processing requirements for three lignocellulosic feedstocks—soybean hulls, wheat straw, and de-starched wheat bran. They were ground with a hammer mill to investigate how differences in composition and particle size affect the hydrolysis process. Enzyme hydrolysis was conducted using cellulase from Trichoderma reesei at 50°C and pH 5. Ground fractions were also subjected to dilute sulfuric acid treatment at 125°C, 15 psi for 30 min prior to cellulase treatment. Reducing particle size of biomass resulted in segregated components of feedstock. Grinding wheat straw to particle size <132 μm resulted in measured lignin content from 20% to ≈5% and reduced hemicellulose content. Reducing lignin content increased the effectiveness of enzyme hydrolysis of wheat straw. Particles sized <132 μm exhibited the highest soluble sugar release upon hydrolysis for all three feedstocks studied. Hemicellulose digestion improved with dilute sulfuric acid treatment with residual hemicellulose content <5% in all three feedstocks after acid treatment. This enhanced the cellulase action and resulted in approximately 1.6-fold increase in sugar availability in de-starched wheat bran and ≈1.5-fold for wheat straw and soybean hulls. Higher sugar availability in wheat bran after acid-mediated enzyme treatment correlated to higher ethanol yields during yeast fermentation compared with soybean hulls and wheat straw.

Dilute acid-soluble phosphorus in fresh air-borne tephras and fixation with an increase in active aluminum and iron

Fresh rhyolite-to-andesite tephras ground to less than 0.15 mm particles contained dilute acid-soluble phosphorus (P) as in the case of cultivated upland soils in Japan. The amount of P determined by Truog extraction (Truog P) ranged between 119 and 784 mg P2O5 kg-1 in 12 rhyolite-to-andesite tephras, and that determined by a modified Bray P2 extraction method (modified Bray P2) ranged between 133 and 812 mg P2O5 kg-1. In contrast, the Truog P-content in fresh basaltic andesite-to-basalt tephras was only 3.4–23 mg P2O5 kg-1, and the modified Bray P2-content was in the range of 41–185 mg P2O5 kg-1, although the total P-content of the two tephra groups was in almost the same range. Among 12 rhyolite-to-andesite tephras, those from Mt. Usu that erupted in 1977 and from Mt. Pinatubo that erupted in 1991 were selected for detailed studies. Fine particle size fractions of these tephras showed higher Truog P values than the coarse ones. The Truog P values further increased in the heavy fraction with a particle density of 2.8 or greater. In this heavy fraction, apatite was detected by energy dispersive X-ray (EDX) analysis, indicating the contribution of the mineral to the high Truog P. Dilute sulfuric acid treatment of the tephras at 80°C for 15 d followed by neutralization increased the amount of active Al and Fe and decreased the Truog P values of these tephras. These results suggested that the amount of apatite rapidly decreased with weathering in volcanic ash soils.