Synergistic Leaching of Titanium, Aluminum, and Magnesium Components during Dilute Acid Pressure Treatment of High-Titanium Blast Furnace Slag.

This study focuses on an improved leaching process through the combination of pressurized conditions and direct filtration of acid leaching slurry, which is conductive to improving the filterability of acid leaching systems and the extraction rates of Ti, Al, and Mg components. The effects of sulfuric acid concentration, reaction temperature, particle size of materials, acid-slag ratio, and reaction time on the leaching efficiency were systematically investigated. The results showed that pressurization significantly enhances the filtration efficiency of the reaction slurry. Under the same filtration time, the filtration efficiency increased from 46% under ordinary pressure to 78% under pressurized conditions. Moreover, under the optimal reaction conditions, the extraction rates of Ti, Al, and Mg components were more than 88.21%, 97.8%, and 96.31%, respectively. Additionally, XRD and FTIR showed that titanium oxide sulfate hydrate crystals were produced in the acid-leached residues when the reaction temperature exceeded 190 °C, thereby reducing the extraction rate of Ti component. And the XRD pattern shows that when the reaction temperature is maintained at 190 °C and the reaction time is extended to 150 min, titanium oxide sulfate hydrate crystals will be formed to reduce the extraction rate of the Ti component. In summary, this study not only provides important theoretical support for the resource utilization of high-titanium blast furnace slag but also offers a feasible solution for efficient extraction and convenient filtration, thus holding significant academic and practical implications.

Implementing dilute acid pretreatment coupled with solid acid catalysis and enzymatic hydrolysis to improve bioconversion of bamboo shoot shells.

Exploiting bamboo shoot shells (BSS) as feedstocks for biorefining is a crucial scheme to advance the bioavailability of bamboo shoots. This work applied traditional dilute sulfuric acid pretreatment (DAP) to treat BSS and simultaneously prepared the solid-acid-catalyst by using BSS as carbon-based carriers. The biocatalysis of the prehydrolysate from DAP and enzymatic hydrolysis of pretreated BSS was subsequently performed to achieve efficient bioconversion of its carbohydrates. The results displayed that 0.1 g/L H2SO4 employed in DAP was the optimal condition for furfural conversion of BSS during biocatalysis, reaching the maximum of 41%. Meanwhile, the enzymatic hydrolysis efficiency of the pretreated BSS also reached the maximum of 97%. This increment of efficiency was ascribed to the enhancement of accessibility and cellulosic crystal size, and also the reduction of surface area of lignin in BSS. Ultimately, the efficient bioutilization of BSS and bioconversion of its carbohydrates were realized by DAP technology.

A Detoxification-Free Process for Enhanced Ethanol Production From Corn Fiber Under Semi-Simultaneous Saccharification and Fermentation.

Corn fiber, a by-product from the corn-processing industry, is an attractive feedstock for cellulosic ethanol because of its rich carbohydrate content (mainly residual starch, cellulose, and hemicellulose), abundant reserves, easy collection, and almost no transportation cost. However, the complex structure and components of corn fiber, especially hemicellulose, make it difficult to be effectively hydrolyzed into fermentable sugars through enzymatic hydrolysis. This study developed a simple and easy industrialized process without detoxification treatment for high-yield ethanol produced from corn fiber. Corn fiber was pretreated by dilute acid under the conditions optimized by Box-Behnken design (0.5% H2SO4 at 105°C for 43 min), and 81.8% of total sugars, including glucose, xylose, and arabinose, could be recovered, then the mixture (solid and hydrolysates) was directly used for semi-simultaneous saccharification and fermentation without detoxification, and ethanol yield reached about 81% of the theoretical yield.

Fermentable sugars production from wheat bran and rye bran: response surface model optimization of dilute sulfuric acid hydrolysis.

ABSTRACTOptimization of hydrolysis conditions of lignocellulosic biomass is crucial to able to produce value-added products by fermentation. This study not only determines optimal dilute sulfuric acid (H2SO4) hydrolysis conditions of wheat bran (WB) and rye bran (RB) by using one-factor-at-a-time method and subsequently Box-Behnken design but also elucidates chemical composition of hydrolysates yielded under optimal hydrolysis conditions. Based on the results, optimal hydrolysis conditions of WB and RB were 121 and 130°C of temperature, 1/8 and 1/8 w/v of solid to liquid ratio, 2.66 and 1.58% v/v of dilute H2SO4 ratio, and 30 and 16 min of implementation time, respectively. Hydrolysates obtained from WB and RB at these conditions contained 72.7 (0.58 g sugar/g biomass) and 89.4 g/L (0.72 g sugar/g biomass) of reducing sugar concentration, respectively. Hydrolysis rates of WB and RB were 87.79 and 91.33%, respectively. Main reducing sugar in RB hydrolysate was glucose with 31.17 g/L (0.25 g glucose/g biomass) while glucose and xylose were the main monosaccharides with 20.90 (0.17 g glucose/g biomass) and 18.69 g/L (0.15 g xylose/g biomass) in WB hydrolysate, respectively. With acidic hydrolysis of WB and RB, inhibitors such as phenolics, 5-Hydroxymethylfurfural, 2-Furaldehyde (not for RB), acetic acid, and formic acid (not for WB) formed. Catalytic efficiency values of H2SO4 for WB and RB were 15.2 and 24.4 g /g, respectively, indicating that inhibitor concentration in WB hydrolysate was higher than that of RB. These results indicated that WB and RB have a high potential in production of value-added products by fermentation.

Improvement of Nicotine Removal and Ethanol Fermentability From Tobacco Stalk by Integration of Dilute Sulfuric Acid Presoak and Instant Catapult Steam Explosion Pretreatment.

The nicotine from tobacco stalk showed obvious inhibitory effect on the activity of cellulase and fermentability of microorganisms, which seriously hinders the utilization of tobacco stalk. Dilute sulfuric acid presoak of tobacco stalk was used to enhance the performance of instant catapult steam explosion (ICSE) for tobacco stalk pretreatment. The presoak was beneficial to break the recalcitrant structure of tobacco stalk, reduce nicotine content to relieve the inhibition on the activity of cellulase and metabolism of microorganisms, and promote the performance of enzymatic hydrolysis and ethanol fermentation. The optimized 0.8% sulfuric acid (w/w) presoak-integrated ICSE pretreatment resulted in 85.54% nicotine removal from tobacco stalk; meanwhile, the total sugar concentration from enzymatic hydrolysis of pretreated tobacco stalk increased from 33.40 to 53.81 g/L (the ratio of dry tobacco stalk to water was 1:8, w/w), ethanol concentration increased 103.36% from 5.95 to 12.10 g/L in flask, compared with separate ICSE pretreatment. Finally, the ethanol concentration achieved the highest 23.53 g/L in a 5-L fermenter with the ethanol yield from the glucose of tobacco stalk hydrolysate achieving 71.40% by increasing the solid loading of the tobacco stalk in the enzymatic hydrolysis process (the ratio of dry tobacco stalk to water was 1:4, w/w). These results achieved the expected purpose of efficient utilization of discarded tobacco stalk.

Comprehensive investigation of multiples factors in sulfuric acid pretreatment on the enzymatic hydrolysis of waste straw cellulose.

The prerequisite for cellulosic biochemical production from lignocellulosic materials is efficient enzymatic hydrolysis that is a complicated heterogeneous catalytic process and affected by the complex lignin-cellulose-hemicellulose network. Understanding the main influencing factors for enzymatic hydrolysis is of substantial significance to guide the design of a biorefinery process. An experimental study of the pretreatment indicated that acid pretreatment is preferable for herbaceous feedstocks. Therefore, the classic dilute sulfuric acid pretreatment was utilized to hydrolyze and remove hemicellulose from three representative types of agricultural straws at various intensities. From the enzymatic hydrolysis of residual cellulose perspective, the crystallinity index and enzyme accessibility of the pretreated materials were also mathematically correlated to hemicellulose removals, respectively. For the better insight and understanding of the mathematical logics, the linear and nonlinear kinetic models were therefore compared, and the relationship was established by the five-parameter logistic equations and Allosteric sigmoidal models with well fittings.

The key role of delignification in overcoming the inherent recalcitrance of Chinese fir for biorefining.

The enzymatic digestibility of softwood is hindered for its highly recalcitrant nature to enzymatic attack. In this study, the effects of dilute sulfuric acid pretreatment (DSAP), acidic sodium chlorite pretreatment (SCP), and their combined pretreatments (DSA-SCP and SC-DSAP) on Chinese fir sawdust were investigated, respectively. Results demonstrated that lignin was the most important obstacle, and digestibility increased linearly with lignin removal yield. Furthermore, the results revealed that the order of sequential pretreatment significantly affected the delignification, and hemicellulose should be removed first. Compared to SC-DSAP, DSA-SCP involving the hemicellulose-removal-first strategy exhibited higher delignification efficiency. DSA-SCP caused lignin removal of 92.3% and the enzymatic hydrolysis was high of 97.9%. Finally, a regression model with high reliability was established to quickly evaluate pretreatment process. In summary, this study highlighted the importance of delignification for saccharification of softwood and unveiled the effect of hemicellulose on delignification.

Preparation of nanocellulose in high yield via chemi-mechanical synergy.

Nanocellulose has gained increasing attention due to its excellent properties and wide application prospect. However, fast and low-waste preparation of nanocellulose is still challenging. Here, a time-saving and low-cost chemi-mechanical method was proposed to prepare cellulose nanocrystals (D-CNCs) and cellulose nanofibers (D-CNFs) by dilute sulfuric acid hydrolysis and the homogenization of the un-hydrolyzed cellulose residues, respectively. After hydrolyzed by 0.3 wt% sulfuric acid at 160 °C for 2 h, the diameter and length distribution of the obtained D-CNCs were 16 ∼ 45 nm and 150 ∼ 600 nm, respectively. The yield of D-CNCs and D-CNFs reached to 15.78 % and 69.11 %. The thermostability of D-CNCs was more superior to CNCs manufactured by 64 wt% sulfuric acid. In conclusion, this approach offers a promising strategy for high yield of nanocellulose due to its easy operation and low pollution.

Xylooligosaccharides production from a sugarcane biomass mixture: Effects of commercial enzyme combinations on bagasse/straw hydrolysis pretreated using different strategies.

Xylooligosaccharides (XOS) are non-digestible food ingredients with prebiotic properties for selectively promoting the growth of probiotics, which provide many health benefits and several applications in the food and pharmaceutical industry. The objective of this study was to optimize the concentration of commercial hemicellulases for the production of XOS, with a 2-6 polymerization degree, using a mixture of sugarcane bagasse and straw pretreated with ionic liquid or diluted sulfuric acid. The concentrations of enzymes endo-1,4-xylanase (NS50030, Novozyme®) and α-L-arabinofuranosidase (GH51) (Megazyme®) were optimized using a central composite rotatable design (CCRD). The xylooligosaccharides (XOS) released by hydrolysis were analyzed via capillary electrophoresis and quantified with HPAEC-PAD. The XOS profile obtained from the hydrolisis of the pretreated sugarcane biomass mixture (MPSA) was similar to that obtained with the hydrolisis of MBX, which provided higher xylobiose (X2) concentration. Our results also demonstrated that pretreatment with an ionic liquid favored the requirement of lower enzyme concentration in enzymatic hydrolysis for having provided a biomass with lower lignin content than the pretreatment with dilute sulfuric acid. It required up to 20% less of the optimum concentration of the endo-1,4-xylanase mixture to achieve similar values to those obtained with the biomass pretreated with dilute sulfuric acid, representing a possible alternative to reduce enzymatic cost.

Effect of dilute acid pretreatment on the saccharification and fermentation of rye straw.

This research shows the effect of dilute acid pretreatment with various sulfuric acid concentrations (0.5-2.0% [wt/vol]) on enzymatic saccharification and fermentation yield of rye straw. After pretreatment, solids of rye straw were suspended in Na citrate buffer or post-pretreatment liquids (prehydrolysates) containing sugars liberated after hemicellulose hydrolysis. Saccharification was conducted using enzymes dosage of 15 or 25 FPU/g cellulose. Cellulose saccharification rate after rye straw pretreatment was enhanced by performing enzymatic hydrolysis in sodium citrate buffer in comparison with hemicellulose prehydrolysate. The maximum cellulose saccharification rate (69%) was reached in sodium citrate buffer (biomass pretreated with 2.0% [wt/vol] H2 SO4 ). Lignocellulosic complex of rye straw after pretreatment was subjected to separate hydrolysis and fermentation (SHF) or separate hydrolysis and co-fermentation (SHCF). The SHF processes conducted in the sodium citrate buffer using monoculture of Saccharomyces cerevisiae (Ethanol Red) were more efficient compared to hemicellulose prehydrolysate in respect with ethanol yields. Maximum fermentation efficiency of SHF processes obtained after rye straw pretreatment at 1.5% [wt/vol] H2 SO4 and saccharification using enzymes dosage of 25 FPU/g in sodium citrate buffer, achieving 40.6% of theoretical yield. However, SHCF process using cocultures of pentose-fermenting yeast, after pretreatment of raw material at 1.5% [wt/vol] H2 SO4 and hydrolysis using enzymes dosage of 25 FPU/g, resulted in the highest ethanol yield among studied methods, achieving 9.4 g/L of ethanol, corresponding to 55% of theoretical yield.

Efficiency of dilute sulfuric acid pretreatment of distillery stillage in the production of cellulosic ethanol.

The aim of this study was to examine suitability of distillery stillage of various origins subjected to dilute sulfuric acidic pretreatment for production of cellulosic ethanol. Optimal conditions for dilute acid pretreatment of: rye and wheat distillery stillage 121 °C, 0.2 M H2SO4, 60 min; maize stillage 131 °C, 0.2 M H2SO4, 60 min. The highest efficiency of enzymatic hydrolysis was achieved for rye and wheat stillage using 1 g of DW and the concentration of cellulolytic enzyme of 24% w/w, and for maize stillage 3 g of DW and enzyme concentration of 24% w/w. The use of rye and wheat stillage for production of ethanol does not require a detoxification process and enables full attenuation of glucose after 48 h of the process. However, the use of maize stillage as a raw material must be preceded by a detoxification process that guarantees a reduction of 5-hydroxymethylfurfural concentration in the fermentation medium.

Dilute sulfuric acid fractionation of Korean food waste for ethanol and lactic acid production by yeast.

Fermentation of food waste biomass can be used to produce biochemicals such as lactic acid and ethanol in a cost-effective manner. Korean food waste (KFW) dewatered by a screw press contains 23.1% glucan on a dry basis and is a potential raw material for the production of ethanol and lactic acid through fermentation. This study was conducted to optimize the dilute acid fractionation conditions for KFW fermentation with respect to the H2SO4 concentration (0-0.8% w/v), temperature (130-190 °C), and residence time (1-128 min) using response surface methodology. Dilute sulfuric acid fractionation was carried out using a 30-mL stainless steel reactor under conditions, and then the dilute acid fractionation was scaled-up in 1-L and 7-L stainless steel reactors under the optimal conditions. The hydrolysate was concentrated, liquid-liquid extracted and neutralized for lactic acid and ethanol production. The highest concentration of glucose obtained from the KFW was 26.4 g/L using fractionation with 0.37% w/v H2SO4 at 156 °C for 123.6 min. Using recombinant Saccharomyces cerevisiae containing a codon-optimized lactate dehydrogenase, the yield of lactic acid and ethanol was 77% of the theoretical yield for 17.4 g/L of fermentable sugar at pH 5.5. Additionally, the yield of ethanol produced by Issatchenkia orientalis was 89% of the theoretical yield for 25 g/L of fermentable sugar at pH 3.

Production of Bio-Ethanol by Integrating Microwave-Assisted Dilute Sulfuric Acid Pretreated Sugarcane Bagasse Slurry with Molasses.

Sugarcane bagasse (SCB) and molasses, known as carbohydrate-rich biomass derived from sugar production, can serve as feedstock for bio-ethanol production. To establish a simple process, the production of bio-ethanol through integration of whole pretreated slurry (WPS) of SCB with molasses was investigated. The results showed that microwave-assisted dilute sulfuric acid pretreatment reduced the formation of toxic compounds compared to a pretreatment process involving "conventional heating". Pretreatment at 180 oC with 10% w v-1 solid loading and 0.5% w v-1 H2SO4 was sufficient to achieve efficient enzymatic saccharification of WPS. By conducting separate hydrolysis and fermentation (SHF), an ethanol yield of 90.12% was obtained from the mixture of WPS and molasses, but the ethanol concentration of 33.48 g L-1 was relatively low. By adopting fed-batch SHF, the ethanol concentration reached 41.49 g L-1. Assuming that the molasses were converted to ethanol at an efficiency of 87.21% (i.e., ethanol was obtained from fermentation of molasses alone), the ethanol yield from WPS when a mixture of WPS and molasses was fermented was 78.30%, which was higher than that of enzymatic saccharification of WPS (73.53%). These findings suggest that the production of bio-ethanol via integration of WPS with molasses is a superior method. Graphical Abstract ᅟ.

Lower pressure heating steam is practical for the distributed dry dilute sulfuric acid pretreatment.

Most studies paid more attention to the pretreatment temperature and the resulted pretreatment efficiency, while ignored the heating media and their scalability to an industry scale. This study aimed to use a relative low pressure heating steam easily provided by steam boiler to meet the requirement of distributed dry dilute acid pretreatment. The results showed that the physical properties of the pretreated corn stover were maintained stable using the steam pressure varying from 1.5, 1.7, 1.9 to 2.1MPa. Enzymatic hydrolysis and high solids loading simultaneous saccharification and fermentation (SSF) results were also satisfying. CFD simulation indicated that the high injection velocity of the low pressure steam resulted in a high steam holdup and made the mixing time of steam and solid corn stover during pretreatment much shorter in comparison with the higher pressure steam. This study provides a design basis for the boiler requirement in distributed pretreatment concept.

Effects of fertilizer application and dry/wet processing of Miscanthus x giganteus on bioethanol production.

The effects of wet and dry processing of miscanthus on bioethanol production using simultaneous saccharification and fermentation (SSF) process were investigated, with wet samples showing higher ethanol yields than dry samples. Miscanthus grown with no fertilizer, with fertilizer and with swine manure were sampled for analysis. Wet-fractionation was used to separate miscanthus into solid and liquid fractions. Dilute sulfuric acid pretreatment was employed and the SSF process was performed with saccharomyces cerevisiae and a cocktail of enzymes at 35°C. After pretreatment, cellulose compositions of biomass of the wet samples increased from 61.0-67.0% to 77.0-87.0%, which were higher than the compositions of dry samples. The highest theoretical ethanol yield of 88.0% was realized for wet processed pretreated miscanthus, grown with swine manure. Changes to the morphology and chemical composition of the biomass samples after pretreatment, such as crystallinity reduction, were observed using SEM and FTIR. These changes improved ethanol production.

Long term storage of dilute acid pretreated corn stover feedstock and ethanol fermentability evaluation.

This study reported a new solution of lignocellulose feedstock storage based on the distributed pretreatment concept. The dry dilute sulfuric acid pretreatment (DDAP) was conducted on corn stover feedstock, instead of ammonia fiber explosion pretreatment. Then the dry dilute acid pretreated corn stover was stored for three months during summer season with high temperature and humidity. No negative aspects were found on the physical property, composition, hydrolysis yield and ethanol fermentability of the long term stored pretreated corn stover, plus the additional merits including no chemicals recovery operation, anti-microbial contaminant environment from stronger acid and inhibitor contents, as well as the mild and slow hydrolysis in the storage. The new pretreatment method expanded the distributed pretreatment concept of feedstock storage with potential for practical application.

High ethanol fermentation performance of the dry dilute acid pretreated corn stover by an evolutionarily adapted Saccharomyces cerevisiae strain.

Ethanol fermentation was investigated at the high solids content of the dry dilute sulfuric acid pretreated corn stover feedstock using an evolutionary adapted Saccharomyces cerevisiae DQ1 strain. The evolutionary adaptation was conducted by successively transferring the S. cerevisiae DQ1 cells into the inhibitors containing corn stover hydrolysate every 12h and finally a stable yeast strain was obtained after 65 days' continuous adaptation. The ethanol fermentation performance using the adapted strain was significantly improved with the high ethanol titer of 71.40 g/L and the high yield of 80.34% in the simultaneous saccharification and fermentation (SSF) at 30% solids content. No wastewater was generated from pretreatment to fermentation steps. The results were compared with the published cellulosic ethanol fermentation cases, and the obvious advantages of the present work were demonstrated not only at the high ethanol titer and yield, but also the significant reduction of wastewater generation and potential cost reduction.

Use of Empty Fruit Bunches from the oil palm for bioethanol production: a thorough comparison between dilute acid and dilute alkali pretreatment.

In the present work, two pretreatment techniques using either dilute acid (H2SO4) or dilute alkali (NaOH) have been compared for producing bioethanol from Empty Fruit Bunches (EFBs) from oil palm tree, a relevant feedstock for tropical countries. Treatments' performances under different conditions have been assessed and statistically optimized with respect to the response upon standardized enzymatic saccharification. The dilute acid treatment performed at optimal conditions (161.5°C, 9.44 min and 1.51% acid loading) gave 85.5% glucose yield, comparable to those of other commonly investigated feedstocks. Besides, the possibility of using fibers instead of finely ground biomass may be of economic interest. Oppositely, treatment with dilute alkali has shown lower performances under the conditions explored, most likely given the relatively significant lignin content, suggesting that the use of stronger alkali regime (with the associated drawbacks) is unavoidable to improve the performance of this treatment.

Dilute sulfuric acid pretreatment of corn stover for enzymatic hydrolysis and efficient ethanol production by recombinant Escherichia coli FBR5 without detoxification.

A pretreatment strategy for dilute H2SO4 pretreatment of corn stover was developed for the purpose of reducing the generation of inhibitory substances during pretreatment so that a detoxification step is not required prior to fermentation while maximizing sugar yield. The optimal conditions for pretreatment of corn stover (10%, w/v) were: 0.75% H2SO4, 160°C, and 0-5 min holding time. The conditions were chosen based on maximum glucose release after enzymatic hydrolysis, minimum loss of pentose sugars and minimum formation of sugar degradation products such as furfural and hydroxymethyl furfural. The pretreated corn stover after enzymatic saccharification generated 63.2 ± 2.2 and 63.7 ± 2.3 g total sugars per L at 0 and 5 min holding time, respectively. Furfural production was 0.45 ± 0.1 and 0.87 ± 0.4 g/L, respectively. The recombinant Escherichia coli strain FBR5 efficiently fermented non-detoxified corn stover hydrolyzate if the furfural content is <0.5 g/L.