Organic Acid Pretreatment Research Articles

Evaluation of biomass pretreatment to optimize process factors for different organic acids via Box-Behnken RSM method.

Biomass, as renewable energy source, is of importance to investigate to extend the conversion yield by microorganism. Because of lignocellulosic structure, biomass must be pretreated with a process, frequently inorganic acid has to be used with a problem of hazardous byproducts. Organic acid pretreatment is an efficient alternative to be investigated. Sugar beet pulp, as an agro-industrial residue of microorganism, can be utilized by pretreatment, which is usually a costly process. Pretreatment with organic acids creates a great opportunity to convert the process into more economic and effective. Moreover, pressure conditions significantly increase the yield of biodegradable sugar content. In this study, different organic acids of maleic, fumaric, oxalic, and acetic acid pretreatment was investigated to pretreatment of sugar beet pulp, which came vast amount from factories, under pressure and non-pressure conditions via Box–Behnken method to estimate optimum point of acid ratio (1, 3, 5%), time (10, 27.5, 45 min), and solid ratio factors (3, 6.5, 10%) for highest degradation. Results were also evaluated economically. As a result of the experiments, it was observed that acetic acid gave the best result with 409.16 g/L total sugar concentration than the other organic acids. The highest TS concentration of maleic, oxalic, and fumaric acid were 97.26, 97.85, and 91.37 g/L, respectively, under pressure. According to economical evaluation, owing to lower market price and highest TS formation yield, pretreatment cost of acetic acid pretreatment was found averagely 1.51 $/gTS under pressure conditions.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10163-021-01276-7.

Panax ginseng-Derived Extracellular Vesicles Facilitate Anti-Senescence Effects in Human Skin Cells: An Eco-Friendly and Sustainable Way to Use Ginseng Substances.

Ginseng is a traditional herbal medicine in eastern Asian countries. Most active constituents in ginseng are prepared via fermentation or organic acid pretreatment. Extracellular vesicles (EVs) are released by most organisms from prokaryotes to eukaryotes and play central roles in intra- and inter-species communications. Plants produce EVs upon exposure to microbes; however, their direct functions and utility for human health are barely known, except for being proposed as delivery vehicles. In this study, we isolated EVs from ginseng roots (GrEVs) or the culture supernatants of ginseng cells (GcEVs) derived from Panax ginseng C.A. Meyer and investigated their biological effects on human skin cells. GrEV or GcEV treatments improved the replicative senescent or senescence-associated pigmented phenotypes of human dermal fibroblasts or ultraviolet B radiation-treated human melanocytes, respectively, by downregulating senescence-associated molecules and/or melanogenesis-related proteins. Based on comprehensive lipidomic analysis using liquid chromatography mass spectrometry, the lipidomic profile of GrEVs differed from that of the parental root extracts, showing significant increases in 70 of 188 identified lipid species and prominent increases in diacylglycerols, some phospholipids (phosphatidylcholine, phosphatidylethanolamine, lysophosphatidylcholine), and sphingomyelin, revealing their unique vesicular properties. Therefore, our results imply that GEVs represent a novel type of bioactive and sustainable nanomaterials that can be applied to human tissues for improving tissue conditions and targeted delivery of active constituents.

Degumming silk by CO2 supercritical fluid and their dyeing ability with plant indigo

Degumming silk by CO₂ supercritical fluid and their dyeing ability with plant indigo

Microwave assisted dilute organic acid pre-treatment of oil palm empty fruit bunch to improve enzyme accessibility

The depletion of fossil fuel is intriguing for researchers to find sustainable energy. Oil palm empty fruit bunch (OPEFB) is abundant biomass in Indonesia which is potential to be converted into bioethanol because of its high cellulose content. Suitable pre-treatment could increase the effectiveness of cellulose conversion into sugars. The aim of this study is to evaluate the effectiveness of Microwave-assisted Oxalic Acid pre-treatment (MOxA) and Enzymatic Hydrolysis (EH) to improve enzyme accessibility through variation of heating temperature, irradiation time, and EH incubation time. The higher the microwave heating temperature, longer irradiation time, and longer EH incubation time, the higher the glucose yield per pulp (GY) and reducing sugar yield (RSY) were observed. After MOxA at 200°C-15 min, as much as 43.22 % GY per initial biomass was obtained by EH for 10 days. SEM images showed more ruptures on the surface area of OPEFB fibre after MOxA that supported in increasing of enzyme digestibility. The XRD spectra demonstrated that the crystallinity index (CI) increased after MOxA because pre-treatment reduced amorphous components in the biomass. In addition, the FTIR spectra showed that peak intensity at 1714 cm−1 corresponded to hemicellulose was gradually reduced after MOxA while peaks corresponded to lignin was more discernible.

Organic Acid Pretreatment of Oil Palm Trunk Biomass for Succinic Acid Production

Oil palm trunk (OPT) is a promising lignocellulosic biomass for sugar production due to its abundant availability, low-cost and high carbohydrate content. Organic acids have been suggested as an alternative to sulphuric acid pretreatment due to their lower hazardous properties. Various organic acids (citric acid, formic acid and oxalic acid) of different concentration (0.5–5.0%) were assessed to find a suitable catalyst in hydrolysing oil palm trunk biomass (OPTB) for different reaction time (15–120 min) at a fixed temperature (120 °C), and expressed in a combined severity factor (CSF) to allow for xylose selectivity and their performance comparison. Of various organic acids used, oxalic acid was shown to be the most effective in solubilizing hemicellulose of OPTB, recovering a maximum xylose of ~ 61.2% at a CSF of 0.97. Nevertheless, citric acid-derived hydrolysate was more potent for succinic acid fermentation by Actinobacillus succinogenes 130Z, showing optimal succinic acid titer of 10.62 g/L and yield of 0.47 g/g, which were two-fold higher than those without acid pretreatment. The capability of A. succinogenes 130Z in utilising both glucose and xylose of OPTB hydrolysates supports development of bio-based succinic acid using oil palm biomass.

Comparative Evaluation of Organic Acid Pretreatment of Eucalyptus for Kraft Dissolving Pulp Production.

Pretreatment is an essential process for the extensive utilization of lignocellulose materials. The effect of four common organic acid pretreatments for Kraft dissolving pulp production was comparatively investigated. It was found that under acidic conditions, hemicellulose can be effectively removed and more reducing sugars can be recovered. During acetic acid pretreatment, lignin that was dissolved in acetic acid could form a lignin-related film which would alleviate cellulose hydrolysis, while other organic acids caused severe cellulose degradation. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD) were used to characterize the pretreated chips in the process. Lignin droplets were attached to the surface of the treated wood chips according to the SEM results. The FTIR spectrum showed that the lignin peak signal becomes stronger, and the hemicellulose peak signal becomes weaker with acid pretreatment. The XRD spectrum demonstrated that the crystallinity index of the wood chips increased. The acetic acid pretreatment process-assisted Kraft process achieved higher yield (31.66%) and higher α-cellulose (98.28%) than any other organic acid pretreatment. Furthermore, extensive utilization of biomass was evaluated with the acetic acid pretreatment-assisted Kraft process. 43.8% polysaccharide (12.14% reducing sugar and 31.66% dissolving pulp) and 22.24% lignin (0.29% acetic acid lignin and 21.95% sulfate lignin) were recovered during the process. Biomass utilization could reach 66.04%. Acetic acid pretreatment is a promising process for extensive biomass utilization.

Organic acid pretreatment of oil palm trunk biomass for fermentable xylose production

Green alternatives to chemical pretreatment in hydrolysing hemicellulose for efficient biorefineries are very much sought-after. In this study, we aimed to determine the effectiveness of several organic acids in hydrolysing hemicellulose of oil palm trunk biomass (OPTB) to form fermentable xylose. Various organic acids (citric acid, formic acid and oxalic acid) of different concentration (0.5-5.0%) were assessed to find a suitable catalyst in hydrolysing OPTB for reaction time (15-120 min) at a fixed temperature (120°C), aiming for high xylose selectivity. Of these, oxalic acid was shown the most effective in solubilizing hemicellulose from OPTB, producing a maximum xylose yield of ∼70% at the optimum catalyst concentration of 5.0% (w/v) for 120 min. The main components in the hemicellulosic hydrolysate were xylose, 16.26±0.30 g/L; glucose, 2.11±0.04 g/L; arabinose, 0.19±0.05 g/L; acetic acid, 5.59±0.07 g/L and trace amount of furfural and hydroxylmethylfurfural (HMF). The resulting xylose recovery was comparable to the conventional pretreatment using dilute sulphuric acid, thus provides an alternative approach of biomass pretreatment for process improvement. The fermentability of xylose from the hemicellulosic hydrolysate was further evaluated for succinic acid production.

Valorization of cashew apple bagasse using acetic acid pretreatment: Production of cellulosic ethanol and lignin for their use as sunscreen ingredients

The present study focuses on the fractionation of cashew apple bagasse via a pretreatment using acetic acid as a delignifying agent and sulfuric acid as an external catalyst. As expected, the concentrations of both acids and the incubation time dramatically affected delignification and hemicellulose solubilization. Under the optimal pretreatment conditions, recycling of the spent liquor had no apparent impact on the chemical composition of the pretreated material, yield of sugar produced via enzymatic hydrolysis (∼37 g/L reducing sugars at 7.5% (w/v) solid loading), or yield of ethanol obtained via fermentation with Saccharomyces cerevisiae (∼16 g/L at 10% (w/v) solid loading). The lignin recovered from the spent liquor showed a good ultraviolet protective effect; the addition of 5% (w/w) of the biopolymer increased the sun protection factor of a commercial sunscreen lotion from 21.62 to 40.71. The combined use of hydrogen peroxide and ultraviolet radiation reduced the organosolv lignin color (absorbance at 450 nm was four times lower) owing to aromatic ring cleavage, but cosmetics containing whitened organosolv lignin had low sun protection factor values. In summary, the results obtained in this study demonstrate the utility of organic acid pretreatment in the valorization of lignocellulosic materials.

Effect of organic acid pretreatment of water hyacinth on enzymatic hydrolysis and biogas and bioethanol production

Due to rapid growth and uncontrolled spreading of water hyacinth in aquatic natural and urban niches, the conversion of this weed to value-added chemicals and biofuels leads to the reduction of pollution and greenhouse effect. The rate-limiting step of the conversion process is hydrolysis reaction of lignocellulosic biomass to sugars, which are subsequently converted to biochemicals and biofuels. To improve the enzymatic hydrolysis efficiency of water hyacinth, the organic acid pretreatments were conducted in this study by using two types of organic acids, including oxalic acid and citric acid. The pretreatment parameters, including pretreatment time, pretreatment temperature, and acid concentration were optimized by using Response Surface Methodology (RSM) based on Box-Behnken design. The highest reducing sugar concentration at 66.92 mg/100 mg-biomass was obtained when using oxalic acid pretreatment. The effects of organic acids on biogas and bioethanol production were observed compared to unpretreated water hyacinth. The biogas and bioethanol yields were increased for 75.61% and 23.26% when using citric acid and oxalic acid pretreatment, respectively. The improvement of biofuel production from water hyacinth by organic acid pretreatment suggested the possibility to applications and solutions in biorefinery industry and environmental situation.

Effect of Hydrothermal, Phytase, or Organic Acid Pretreatments of Canola Meal on Phytate Level of the Meal

The objective of this study was to investigate the effect of pretreatment of canola meal with hydrothermal processing, phytase, and organic acid on phytate degradation. Six experiments were conducted processing canola meal in a hydrothermal reactor with different moisture conditions (15-350%), acid additions (hydrochloric acid, citric acid, malic acid, and lactic acid), pH (pH 4, 5, and 6), incubation times (30, 45, and 60 min), and phytase enzymes (‘Quantum Blue’ and ‘Finase’). The study revealed that although hydrothermal pretreatment of canola meal with phytase and higher moisture (200-350%) would allow 24.8-36% phytate breakdown, and a higher moisture addition (200%) combined with organic acid increased even further to 46.6%, lower moisture (50 and 100%) and organic acid was still effective in reducing phytate (by 7.9-19.4%). Optimal pH and incubation time in hydrothermal reactor for phytase efficacy were determined to be pH 4 and 5 and 30 to 60 min. Still, the results of the current study suggest that pretreatments should be further evaluated to optimize the efficacy of enzyme and organic acids as prebiotics to reduce anti-nutrients in canola meal, thus improving its utilization for livestock and reducing excretion to environment.

Synergism of organic acid and deep eutectic solvents pretreatment for the co-production of oligosaccharides and enhancing enzymatic saccharification

A novel pretreatment using organic acid synergism with deep eutectic solvents (DESs) was developed to the co-production of oligosaccharides, especially for the functional oligosaccharides, and enhancement of corn straws enzymatic saccharification. It was found that lactic acid (Lac) pretreatment combined with choline chloride/Lac system could not only selectively convert the hemicellulose to xylo-oligosaccharides (XOS), which account for 89.7% of total xylose in prehydrolysate (the functional XOS (DP < 5) took up about 35%), but also significantly promote the glucose release (33.2 g/100 g material) and well lignin separation (representing 40.9% in whole process), which better than the single organic pretreatment at higher modified severity index (SI). Structural features of various solids were characterized to better comprehend how hemicellulose and lignin removal influenced enzymatic hydrolysis. This work offered the mild and potential method to co-produce fermentable sugars with the effective separation and valorization of lignin.

Sustainable production of pure silica from rice husk waste in Kazakhstan

This study aimed at developing a new synthesis method for the production of high purity silica from rice husks originated from different regions of Kazakhstan. The proposed eco-friendly method is compared with the conventional one reported in the literature which is accompanied by the use of significant amount of inorganic alkali and acids and direct combustion. In order to reduce the environmental impact, the mineral acid pre-treatment stage was either removed or replaced with organic acid pre-treatment, which reduced the amount of chemicals used during the synthesis and treatment process. The calcination temperature of 600 °C was selected based on thermogravimetric analysis. The average purity of silica samples obtained via different methods ranged from 84.81 to 99.66 wt%. The purity of the produced silica by use of the greener method was high reaching 98.67% with surface area up to 625 m2/g.

Comparison of Dilute Organic Acid Pretreatment and a Comprehensive Exploration of Citric Acid Pretreatment on Corn Cob

Comparison of Dilute Organic Acid Pretreatment and a Comprehensive Exploration of Citric Acid Pretreatment on Corn Cob

Effects of inorganic and organic acid pretreatments on the hydrothermal liquefaction of municipal secondary sludge

In this study, the effects of inorganic (HCl, HNO3 and H2SO4) and organic (HCOOH, CH3COOH and HOOCCOOH) acid pretreatments on the hydrothermal liquefaction (HTL) of municipal secondary sludge (MSS) were investigated. The results showed that all acid pretreatments could increase bio-oil yield by changing the proportion of organic matters and ash content in feedstock and thus facilitating the conversion of water soluble product to bio-oil. A maximum bio-oil yield of 26.75 wt% was obtained from the HCl pretreatment which increased 7.5 wt% compared to the blank experiment. Moreover, the inorganic acid pretreatments showed a better performance in terms of enhancing bio-oil quality as their higher heating values (HHVs, 31.83–36.04 MJ/kg) were much higher than that from organic acid pretreatments (24.57–29.22 MJ/kg). The characterization analysis of bio-oil indicated that the HCl pretreatment was most beneficial for the formation of light fraction and increment of hydrocarbon.

Evaluation and Optimization of Organic Acid Pretreatment of Cotton Gin Waste for Enzymatic Hydrolysis and Bioethanol Production

This paper investigates the efficiency of the organic acids on the pretreatment of an industrially generated cotton gin waste for the removal of lignin, thereby releasing cellulose and hemicellulose as fermentable sugar components. Cotton gin waste was pretreated with various organic acids namely lactic acid, oxalic acid, citric acid, and maleic acid. Among these, maleic acid was found to be the most efficient producing maximum xylose sugar (126.05 ± 0.74g/g) at the optimum pretreatment condition of 150°C, 500mM, and 45min. The pretreatment efficiency was comparable to the conventional dilute sulfuric acid pretreatment. A lignin removal of 88% was achieved by treating maleic acid pretreated biomass in a mixture of sodium sulfite and sodium chlorite. The pretreated biomass was further evaluated for the release of sugar by enzymatic hydrolysis and subsequently bioethanol production from hydrolysates. The maximum 686.13g/g saccharification yield was achieved with maleic acid pretreated biomass which was slightly higher than the sulfuric acid (675.26g/g) pretreated waste. The fermentation of mixed hydrolysates(41.75g/l) produced 18.74g/l bioethanol concentration with 2.25g/l/h ethanol productivity and 0.48g/g ethanol yield using sequential use of Saccharomyces cerevisiae and Pichia stipitis yeast strains. The production of bioethanol was higher than the ethanol produced using co-culture in comparison to sequential culture. Thus, it has been demonstrated that the maleic acid pretreatment and fermentation using sequential use of yeast strains are efficient for bioethanol production from cotton gin waste.

Organic acid pretreatment of oil palm trunk: effect on enzymatic saccharification and ethanol production.

Effective lignocellulosic biomass saccharification is one of the crucial requirements of biofuel production via fermentation process. Organic acid pretreatments have been gained much interests as one of the high potential methods for promoting enzymatic saccharification of lignocellulosic materials due to their lower hazardous properties and lower production of inhibitory by-products of fermentation than typical chemical pretreatment methods. In this study, three organic acids, including acetic acid, oxalic acid, and citric acid, were examined for improvement of enzymatic saccharification and bioethanol production from oil palm trunk biomass. Based on response surface methodology, oxalic acid pretreated biomass released the maximum reducing sugar of 144mg/g-pretreated biomass at the optimum condition, which was higher than untreated samples for 2.30 times. The released sugar yield of oil palm trunk also corresponded to the results of FT-IR analysis, which revealed the physical modification of cellulose and hemicellulose surface structures of pretreated biomass. Nevertheless, citric acid pretreatment is the most efficient pretreatment method to improve bioethanol fermentation of Saccharomyces cerevisiae TISTR 5606at 1.94 times higher than untreated biomass. These results highlighted the selection of organic acid pretreatment as a potential method for biofuel production from oil palm trunk feedstocks.

Phenolics and essential mineral profile of organic acid pretreated unripe banana flour

Banana fruit (Musa spp) though rich in essential minerals, has also been implicated for the presence of phytochemicals which nonetheless beneficial, can also act as mineral inhibitors when in forms such as phenolic compounds, phytates and tannins. This study assayed the essential macro and trace minerals as well as phenolic compounds present in unripe banana flour (UBF) obtained from the pulp of four different cultivars. Unripe banana flour was processed by oven drying in a forced air oven dryer at 70°C upon pretreatment with ascorbic, citric and lactic acid. Organic acid pretreatment was done separately on each unripe banana cultivar at concentrations of 10, 15 and 20g/L. Phenolic compounds were profiled using liquid chromatography mass spectrometry electrospray ion (LC-MS-ESI) while essential minerals were determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES) and mass spectroscopy (ICP-MS) respectively. Results of LC-MS-ESI assay of phenolics revealed the presence of flavonoids: epicatechin and myricetin 3-O-rhamnosyl-glucoside in varying concentrations in UBF. Essential mineral profile indicated that Zinc had the least occurrence of 3.55mg/kg (p<0.05), while potassium was the most abundant mineral at 14746.73mg/kg in UBF of all four banana cultivars. Correlation between phenolic compounds and essential minerals using Pearson's Correlation Coefficient test revealed weak and inverse association between flavonoids and most macro and trace minerals present in UBF samples. Organic acid pretreatment thus exhibited little effect on phenolics and essential minerals of UBF samples, though, inhibitory influence of phenolic compounds was recorded on essential minerals.

Effect of Organic Acid Pretreatment on Napier Grass (Pennisetum purpureum) Straw Biomass Conversion

Production of specialty chemicals or bioproducts from lignocellulosic biomass has a major bottleneck at hydrolysis step due to recalcitrant structures of lignocellulose fibrils. Pretreatment is necessary to be executed to enhance saccharification efficiency. This study, the effect of acid pretreatment on lignocellulosic conversion of Napier grass was evaluated based on Response Surface Methodology (RSM). Pretreatment conditions were optimized for oxalic, citric, acetic, and hydrochloric acids. Validation indicated that the models were predictive to magnify the conversion. Hydrochloric acid exhibited highest effectiveness, followed by oxalic, acetic, and citric acids. The optimal conditions were using 0.7% (w/v) hydrochloric acid at 105°C for 60.18 min and using 5.72% (w/v) oxalic acid at 104.66°C for 76.94 min. The obtained sugar yields were low compared to those from rice straws pretreated with the optimal, same acid conditions. The results here suggested the requirement of optimization study before choosing organic acid pretreatment to different types of lignocellulosic biomass.

Optimization of organic acid pretreatment of wheat straw.

The objective of this study was to determine the effectiveness of different organic acids (maleic, succinic, and oxalic acid) on enzymatic hydrolysis and fermentation yields of wheat straw. It was also aimed to optimize the process conditions (temperature, acid concentration, and pretreatment time) by using response surface methodology (RSM). In line with this objective, the wheat straw samples were pretreated at three different temperatures (170, 190, and 210°C), acid concentrations (1%, 3%, and 5%) and pretreatment time (10, 20, and 30 min). The findings show that at extreme pretreatment conditions, xylose was solubilized in liquid phase, causing an increase in cellulose and lignin content of biomass. Enzymatic hydrolysis experiments revealed that maleic and oxalic acids were quite effective at achieving high sugar yields (>90%) from wheat straw. In contrast, the highest sugar yields were 50-60%, when the samples were pretreated with succinic acid, indicating that succinic acid was not as effective. The optimum process conditions for maleic acid were, 210°C, 1.08% acid concentration, and 19.8 min; for succinic acid 210°C, 5% acid concentration, and 30 min; for oxalic acid 210°C, 3.6% acid concentration, and 16.3 min. The ethanol yields obtained at optimum conditions were 80, 79, and 59% for maleic, oxalic and succinic acid, respectively. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1487-1493, 2016.

Enhancement of In Situ Enzymatic Saccharification of Corn Stover by a Stepwise Sodium Hydroxide and Organic Acid Pretreatment

A stepwise pretreatment method that combines sodium hydroxide and organic acid pretreatments was proposed and investigated to maximize the recovery of main constituents of lignocellulose. The sodium hydroxide pretreatment was firstly optimized by a designed orthogonal experiment with the optimum pretreatment conditions determined as 1wt% NaOH at 70°C for 1h, and 60.42% of lignin was successfully removed during this stage. In the second stage, 0.5% acetic acid was selected to pretreat the first-stage solid residue at 80°C for 40min in order to decompose hemicelluloses to soluble oligomers or monomers. Then, the whole slurry was subjected to in situ enzymatic saccharification by cellullase with a supplementation of xylanase to further degrade the xylooligosaccharides generated during the acetic acid pretreatment. The maximum reducing sugar and glucose yields achieved were 20.74 and 12.03g/L, respectively. Furthermore, rapid ethanol fermentation and a yield of 80.3% also testified this pretreatment method, and the in situ saccharification did not bring any negative impact on ethanol fermentation and has a broad application prospect.